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-rw-r--r--Documentation/DocBook/Makefile3
-rw-r--r--Documentation/DocBook/genericirq.tmpl474
-rw-r--r--Documentation/DocBook/kernel-locking.tmpl2
-rw-r--r--Documentation/IRQ.txt22
-rw-r--r--Documentation/RCU/torture.txt34
-rw-r--r--Documentation/arm/Samsung-S3C24XX/Overview.txt35
-rw-r--r--Documentation/arm/Samsung-S3C24XX/S3C2412.txt120
-rw-r--r--Documentation/arm/Samsung-S3C24XX/S3C2413.txt21
-rw-r--r--Documentation/atomic_ops.txt28
-rw-r--r--Documentation/driver-model/overview.txt2
-rw-r--r--Documentation/feature-removal-schedule.txt64
-rw-r--r--Documentation/kdump/gdbmacros.txt2
-rw-r--r--Documentation/kernel-parameters.txt13
-rw-r--r--Documentation/keys-request-key.txt54
-rw-r--r--Documentation/keys.txt29
-rw-r--r--Documentation/pi-futex.txt121
-rw-r--r--Documentation/robust-futexes.txt2
-rw-r--r--Documentation/rt-mutex-design.txt781
-rw-r--r--Documentation/rt-mutex.txt79
-rw-r--r--Documentation/scsi/ppa.txt2
-rw-r--r--Documentation/sound/alsa/ALSA-Configuration.txt106
-rw-r--r--Documentation/video4linux/README.pvrusb2212
-rw-r--r--Documentation/watchdog/pcwd-watchdog.txt75
-rw-r--r--Documentation/watchdog/src/watchdog-simple.c15
-rw-r--r--Documentation/watchdog/src/watchdog-test.c68
-rw-r--r--Documentation/watchdog/watchdog-api.txt56
-rw-r--r--Documentation/watchdog/watchdog.txt23
27 files changed, 2248 insertions, 195 deletions
diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile
index 5a2882d275ba..66e1cf733571 100644
--- a/Documentation/DocBook/Makefile
+++ b/Documentation/DocBook/Makefile
@@ -10,7 +10,8 @@ DOCBOOKS := wanbook.xml z8530book.xml mcabook.xml videobook.xml \
10 kernel-hacking.xml kernel-locking.xml deviceiobook.xml \ 10 kernel-hacking.xml kernel-locking.xml deviceiobook.xml \
11 procfs-guide.xml writing_usb_driver.xml \ 11 procfs-guide.xml writing_usb_driver.xml \
12 kernel-api.xml journal-api.xml lsm.xml usb.xml \ 12 kernel-api.xml journal-api.xml lsm.xml usb.xml \
13 gadget.xml libata.xml mtdnand.xml librs.xml rapidio.xml 13 gadget.xml libata.xml mtdnand.xml librs.xml rapidio.xml \
14 genericirq.xml
14 15
15### 16###
16# The build process is as follows (targets): 17# The build process is as follows (targets):
diff --git a/Documentation/DocBook/genericirq.tmpl b/Documentation/DocBook/genericirq.tmpl
new file mode 100644
index 000000000000..0f4a4b6321e4
--- /dev/null
+++ b/Documentation/DocBook/genericirq.tmpl
@@ -0,0 +1,474 @@
1<?xml version="1.0" encoding="UTF-8"?>
2<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
3 "http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>
4
5<book id="Generic-IRQ-Guide">
6 <bookinfo>
7 <title>Linux generic IRQ handling</title>
8
9 <authorgroup>
10 <author>
11 <firstname>Thomas</firstname>
12 <surname>Gleixner</surname>
13 <affiliation>
14 <address>
15 <email>tglx@linutronix.de</email>
16 </address>
17 </affiliation>
18 </author>
19 <author>
20 <firstname>Ingo</firstname>
21 <surname>Molnar</surname>
22 <affiliation>
23 <address>
24 <email>mingo@elte.hu</email>
25 </address>
26 </affiliation>
27 </author>
28 </authorgroup>
29
30 <copyright>
31 <year>2005-2006</year>
32 <holder>Thomas Gleixner</holder>
33 </copyright>
34 <copyright>
35 <year>2005-2006</year>
36 <holder>Ingo Molnar</holder>
37 </copyright>
38
39 <legalnotice>
40 <para>
41 This documentation is free software; you can redistribute
42 it and/or modify it under the terms of the GNU General Public
43 License version 2 as published by the Free Software Foundation.
44 </para>
45
46 <para>
47 This program is distributed in the hope that it will be
48 useful, but WITHOUT ANY WARRANTY; without even the implied
49 warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
50 See the GNU General Public License for more details.
51 </para>
52
53 <para>
54 You should have received a copy of the GNU General Public
55 License along with this program; if not, write to the Free
56 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston,
57 MA 02111-1307 USA
58 </para>
59
60 <para>
61 For more details see the file COPYING in the source
62 distribution of Linux.
63 </para>
64 </legalnotice>
65 </bookinfo>
66
67<toc></toc>
68
69 <chapter id="intro">
70 <title>Introduction</title>
71 <para>
72 The generic interrupt handling layer is designed to provide a
73 complete abstraction of interrupt handling for device drivers.
74 It is able to handle all the different types of interrupt controller
75 hardware. Device drivers use generic API functions to request, enable,
76 disable and free interrupts. The drivers do not have to know anything
77 about interrupt hardware details, so they can be used on different
78 platforms without code changes.
79 </para>
80 <para>
81 This documentation is provided to developers who want to implement
82 an interrupt subsystem based for their architecture, with the help
83 of the generic IRQ handling layer.
84 </para>
85 </chapter>
86
87 <chapter id="rationale">
88 <title>Rationale</title>
89 <para>
90 The original implementation of interrupt handling in Linux is using
91 the __do_IRQ() super-handler, which is able to deal with every
92 type of interrupt logic.
93 </para>
94 <para>
95 Originally, Russell King identified different types of handlers to
96 build a quite universal set for the ARM interrupt handler
97 implementation in Linux 2.5/2.6. He distinguished between:
98 <itemizedlist>
99 <listitem><para>Level type</para></listitem>
100 <listitem><para>Edge type</para></listitem>
101 <listitem><para>Simple type</para></listitem>
102 </itemizedlist>
103 In the SMP world of the __do_IRQ() super-handler another type
104 was identified:
105 <itemizedlist>
106 <listitem><para>Per CPU type</para></listitem>
107 </itemizedlist>
108 </para>
109 <para>
110 This split implementation of highlevel IRQ handlers allows us to
111 optimize the flow of the interrupt handling for each specific
112 interrupt type. This reduces complexity in that particular codepath
113 and allows the optimized handling of a given type.
114 </para>
115 <para>
116 The original general IRQ implementation used hw_interrupt_type
117 structures and their ->ack(), ->end() [etc.] callbacks to
118 differentiate the flow control in the super-handler. This leads to
119 a mix of flow logic and lowlevel hardware logic, and it also leads
120 to unnecessary code duplication: for example in i386, there is a
121 ioapic_level_irq and a ioapic_edge_irq irq-type which share many
122 of the lowlevel details but have different flow handling.
123 </para>
124 <para>
125 A more natural abstraction is the clean separation of the
126 'irq flow' and the 'chip details'.
127 </para>
128 <para>
129 Analysing a couple of architecture's IRQ subsystem implementations
130 reveals that most of them can use a generic set of 'irq flow'
131 methods and only need to add the chip level specific code.
132 The separation is also valuable for (sub)architectures
133 which need specific quirks in the irq flow itself but not in the
134 chip-details - and thus provides a more transparent IRQ subsystem
135 design.
136 </para>
137 <para>
138 Each interrupt descriptor is assigned its own highlevel flow
139 handler, which is normally one of the generic
140 implementations. (This highlevel flow handler implementation also
141 makes it simple to provide demultiplexing handlers which can be
142 found in embedded platforms on various architectures.)
143 </para>
144 <para>
145 The separation makes the generic interrupt handling layer more
146 flexible and extensible. For example, an (sub)architecture can
147 use a generic irq-flow implementation for 'level type' interrupts
148 and add a (sub)architecture specific 'edge type' implementation.
149 </para>
150 <para>
151 To make the transition to the new model easier and prevent the
152 breakage of existing implementations, the __do_IRQ() super-handler
153 is still available. This leads to a kind of duality for the time
154 being. Over time the new model should be used in more and more
155 architectures, as it enables smaller and cleaner IRQ subsystems.
156 </para>
157 </chapter>
158 <chapter id="bugs">
159 <title>Known Bugs And Assumptions</title>
160 <para>
161 None (knock on wood).
162 </para>
163 </chapter>
164
165 <chapter id="Abstraction">
166 <title>Abstraction layers</title>
167 <para>
168 There are three main levels of abstraction in the interrupt code:
169 <orderedlist>
170 <listitem><para>Highlevel driver API</para></listitem>
171 <listitem><para>Highlevel IRQ flow handlers</para></listitem>
172 <listitem><para>Chiplevel hardware encapsulation</para></listitem>
173 </orderedlist>
174 </para>
175 <sect1>
176 <title>Interrupt control flow</title>
177 <para>
178 Each interrupt is described by an interrupt descriptor structure
179 irq_desc. The interrupt is referenced by an 'unsigned int' numeric
180 value which selects the corresponding interrupt decription structure
181 in the descriptor structures array.
182 The descriptor structure contains status information and pointers
183 to the interrupt flow method and the interrupt chip structure
184 which are assigned to this interrupt.
185 </para>
186 <para>
187 Whenever an interrupt triggers, the lowlevel arch code calls into
188 the generic interrupt code by calling desc->handle_irq().
189 This highlevel IRQ handling function only uses desc->chip primitives
190 referenced by the assigned chip descriptor structure.
191 </para>
192 </sect1>
193 <sect1>
194 <title>Highlevel Driver API</title>
195 <para>
196 The highlevel Driver API consists of following functions:
197 <itemizedlist>
198 <listitem><para>request_irq()</para></listitem>
199 <listitem><para>free_irq()</para></listitem>
200 <listitem><para>disable_irq()</para></listitem>
201 <listitem><para>enable_irq()</para></listitem>
202 <listitem><para>disable_irq_nosync() (SMP only)</para></listitem>
203 <listitem><para>synchronize_irq() (SMP only)</para></listitem>
204 <listitem><para>set_irq_type()</para></listitem>
205 <listitem><para>set_irq_wake()</para></listitem>
206 <listitem><para>set_irq_data()</para></listitem>
207 <listitem><para>set_irq_chip()</para></listitem>
208 <listitem><para>set_irq_chip_data()</para></listitem>
209 </itemizedlist>
210 See the autogenerated function documentation for details.
211 </para>
212 </sect1>
213 <sect1>
214 <title>Highlevel IRQ flow handlers</title>
215 <para>
216 The generic layer provides a set of pre-defined irq-flow methods:
217 <itemizedlist>
218 <listitem><para>handle_level_irq</para></listitem>
219 <listitem><para>handle_edge_irq</para></listitem>
220 <listitem><para>handle_simple_irq</para></listitem>
221 <listitem><para>handle_percpu_irq</para></listitem>
222 </itemizedlist>
223 The interrupt flow handlers (either predefined or architecture
224 specific) are assigned to specific interrupts by the architecture
225 either during bootup or during device initialization.
226 </para>
227 <sect2>
228 <title>Default flow implementations</title>
229 <sect3>
230 <title>Helper functions</title>
231 <para>
232 The helper functions call the chip primitives and
233 are used by the default flow implementations.
234 The following helper functions are implemented (simplified excerpt):
235 <programlisting>
236default_enable(irq)
237{
238 desc->chip->unmask(irq);
239}
240
241default_disable(irq)
242{
243 if (!delay_disable(irq))
244 desc->chip->mask(irq);
245}
246
247default_ack(irq)
248{
249 chip->ack(irq);
250}
251
252default_mask_ack(irq)
253{
254 if (chip->mask_ack) {
255 chip->mask_ack(irq);
256 } else {
257 chip->mask(irq);
258 chip->ack(irq);
259 }
260}
261
262noop(irq)
263{
264}
265
266 </programlisting>
267 </para>
268 </sect3>
269 </sect2>
270 <sect2>
271 <title>Default flow handler implementations</title>
272 <sect3>
273 <title>Default Level IRQ flow handler</title>
274 <para>
275 handle_level_irq provides a generic implementation
276 for level-triggered interrupts.
277 </para>
278 <para>
279 The following control flow is implemented (simplified excerpt):
280 <programlisting>
281desc->chip->start();
282handle_IRQ_event(desc->action);
283desc->chip->end();
284 </programlisting>
285 </para>
286 </sect3>
287 <sect3>
288 <title>Default Edge IRQ flow handler</title>
289 <para>
290 handle_edge_irq provides a generic implementation
291 for edge-triggered interrupts.
292 </para>
293 <para>
294 The following control flow is implemented (simplified excerpt):
295 <programlisting>
296if (desc->status &amp; running) {
297 desc->chip->hold();
298 desc->status |= pending | masked;
299 return;
300}
301desc->chip->start();
302desc->status |= running;
303do {
304 if (desc->status &amp; masked)
305 desc->chip->enable();
306 desc-status &amp;= ~pending;
307 handle_IRQ_event(desc->action);
308} while (status &amp; pending);
309desc-status &amp;= ~running;
310desc->chip->end();
311 </programlisting>
312 </para>
313 </sect3>
314 <sect3>
315 <title>Default simple IRQ flow handler</title>
316 <para>
317 handle_simple_irq provides a generic implementation
318 for simple interrupts.
319 </para>
320 <para>
321 Note: The simple flow handler does not call any
322 handler/chip primitives.
323 </para>
324 <para>
325 The following control flow is implemented (simplified excerpt):
326 <programlisting>
327handle_IRQ_event(desc->action);
328 </programlisting>
329 </para>
330 </sect3>
331 <sect3>
332 <title>Default per CPU flow handler</title>
333 <para>
334 handle_percpu_irq provides a generic implementation
335 for per CPU interrupts.
336 </para>
337 <para>
338 Per CPU interrupts are only available on SMP and
339 the handler provides a simplified version without
340 locking.
341 </para>
342 <para>
343 The following control flow is implemented (simplified excerpt):
344 <programlisting>
345desc->chip->start();
346handle_IRQ_event(desc->action);
347desc->chip->end();
348 </programlisting>
349 </para>
350 </sect3>
351 </sect2>
352 <sect2>
353 <title>Quirks and optimizations</title>
354 <para>
355 The generic functions are intended for 'clean' architectures and chips,
356 which have no platform-specific IRQ handling quirks. If an architecture
357 needs to implement quirks on the 'flow' level then it can do so by
358 overriding the highlevel irq-flow handler.
359 </para>
360 </sect2>
361 <sect2>
362 <title>Delayed interrupt disable</title>
363 <para>
364 This per interrupt selectable feature, which was introduced by Russell
365 King in the ARM interrupt implementation, does not mask an interrupt
366 at the hardware level when disable_irq() is called. The interrupt is
367 kept enabled and is masked in the flow handler when an interrupt event
368 happens. This prevents losing edge interrupts on hardware which does
369 not store an edge interrupt event while the interrupt is disabled at
370 the hardware level. When an interrupt arrives while the IRQ_DISABLED
371 flag is set, then the interrupt is masked at the hardware level and
372 the IRQ_PENDING bit is set. When the interrupt is re-enabled by
373 enable_irq() the pending bit is checked and if it is set, the
374 interrupt is resent either via hardware or by a software resend
375 mechanism. (It's necessary to enable CONFIG_HARDIRQS_SW_RESEND when
376 you want to use the delayed interrupt disable feature and your
377 hardware is not capable of retriggering an interrupt.)
378 The delayed interrupt disable can be runtime enabled, per interrupt,
379 by setting the IRQ_DELAYED_DISABLE flag in the irq_desc status field.
380 </para>
381 </sect2>
382 </sect1>
383 <sect1>
384 <title>Chiplevel hardware encapsulation</title>
385 <para>
386 The chip level hardware descriptor structure irq_chip
387 contains all the direct chip relevant functions, which
388 can be utilized by the irq flow implementations.
389 <itemizedlist>
390 <listitem><para>ack()</para></listitem>
391 <listitem><para>mask_ack() - Optional, recommended for performance</para></listitem>
392 <listitem><para>mask()</para></listitem>
393 <listitem><para>unmask()</para></listitem>
394 <listitem><para>retrigger() - Optional</para></listitem>
395 <listitem><para>set_type() - Optional</para></listitem>
396 <listitem><para>set_wake() - Optional</para></listitem>
397 </itemizedlist>
398 These primitives are strictly intended to mean what they say: ack means
399 ACK, masking means masking of an IRQ line, etc. It is up to the flow
400 handler(s) to use these basic units of lowlevel functionality.
401 </para>
402 </sect1>
403 </chapter>
404
405 <chapter id="doirq">
406 <title>__do_IRQ entry point</title>
407 <para>
408 The original implementation __do_IRQ() is an alternative entry
409 point for all types of interrupts.
410 </para>
411 <para>
412 This handler turned out to be not suitable for all
413 interrupt hardware and was therefore reimplemented with split
414 functionality for egde/level/simple/percpu interrupts. This is not
415 only a functional optimization. It also shortens code paths for
416 interrupts.
417 </para>
418 <para>
419 To make use of the split implementation, replace the call to
420 __do_IRQ by a call to desc->chip->handle_irq() and associate
421 the appropriate handler function to desc->chip->handle_irq().
422 In most cases the generic handler implementations should
423 be sufficient.
424 </para>
425 </chapter>
426
427 <chapter id="locking">
428 <title>Locking on SMP</title>
429 <para>
430 The locking of chip registers is up to the architecture that
431 defines the chip primitives. There is a chip->lock field that can be used
432 for serialization, but the generic layer does not touch it. The per-irq
433 structure is protected via desc->lock, by the generic layer.
434 </para>
435 </chapter>
436 <chapter id="structs">
437 <title>Structures</title>
438 <para>
439 This chapter contains the autogenerated documentation of the structures which are
440 used in the generic IRQ layer.
441 </para>
442!Iinclude/linux/irq.h
443 </chapter>
444
445 <chapter id="pubfunctions">
446 <title>Public Functions Provided</title>
447 <para>
448 This chapter contains the autogenerated documentation of the kernel API functions
449 which are exported.
450 </para>
451!Ekernel/irq/manage.c
452!Ekernel/irq/chip.c
453 </chapter>
454
455 <chapter id="intfunctions">
456 <title>Internal Functions Provided</title>
457 <para>
458 This chapter contains the autogenerated documentation of the internal functions.
459 </para>
460!Ikernel/irq/handle.c
461!Ikernel/irq/chip.c
462 </chapter>
463
464 <chapter id="credits">
465 <title>Credits</title>
466 <para>
467 The following people have contributed to this document:
468 <orderedlist>
469 <listitem><para>Thomas Gleixner<email>tglx@linutronix.de</email></para></listitem>
470 <listitem><para>Ingo Molnar<email>mingo@elte.hu</email></para></listitem>
471 </orderedlist>
472 </para>
473 </chapter>
474</book>
diff --git a/Documentation/DocBook/kernel-locking.tmpl b/Documentation/DocBook/kernel-locking.tmpl
index 158ffe9bfade..644c3884fab9 100644
--- a/Documentation/DocBook/kernel-locking.tmpl
+++ b/Documentation/DocBook/kernel-locking.tmpl
@@ -1590,7 +1590,7 @@ the amount of locking which needs to be done.
1590 <para> 1590 <para>
1591 Our final dilemma is this: when can we actually destroy the 1591 Our final dilemma is this: when can we actually destroy the
1592 removed element? Remember, a reader might be stepping through 1592 removed element? Remember, a reader might be stepping through
1593 this element in the list right now: it we free this element and 1593 this element in the list right now: if we free this element and
1594 the <symbol>next</symbol> pointer changes, the reader will jump 1594 the <symbol>next</symbol> pointer changes, the reader will jump
1595 off into garbage and crash. We need to wait until we know that 1595 off into garbage and crash. We need to wait until we know that
1596 all the readers who were traversing the list when we deleted the 1596 all the readers who were traversing the list when we deleted the
diff --git a/Documentation/IRQ.txt b/Documentation/IRQ.txt
new file mode 100644
index 000000000000..1011e7175021
--- /dev/null
+++ b/Documentation/IRQ.txt
@@ -0,0 +1,22 @@
1What is an IRQ?
2
3An IRQ is an interrupt request from a device.
4Currently they can come in over a pin, or over a packet.
5Several devices may be connected to the same pin thus
6sharing an IRQ.
7
8An IRQ number is a kernel identifier used to talk about a hardware
9interrupt source. Typically this is an index into the global irq_desc
10array, but except for what linux/interrupt.h implements the details
11are architecture specific.
12
13An IRQ number is an enumeration of the possible interrupt sources on a
14machine. Typically what is enumerated is the number of input pins on
15all of the interrupt controller in the system. In the case of ISA
16what is enumerated are the 16 input pins on the two i8259 interrupt
17controllers.
18
19Architectures can assign additional meaning to the IRQ numbers, and
20are encouraged to in the case where there is any manual configuration
21of the hardware involved. The ISA IRQs are a classic example of
22assigning this kind of additional meaning.
diff --git a/Documentation/RCU/torture.txt b/Documentation/RCU/torture.txt
index e4c38152f7f7..a4948591607d 100644
--- a/Documentation/RCU/torture.txt
+++ b/Documentation/RCU/torture.txt
@@ -7,7 +7,7 @@ The CONFIG_RCU_TORTURE_TEST config option is available for all RCU
7implementations. It creates an rcutorture kernel module that can 7implementations. It creates an rcutorture kernel module that can
8be loaded to run a torture test. The test periodically outputs 8be loaded to run a torture test. The test periodically outputs
9status messages via printk(), which can be examined via the dmesg 9status messages via printk(), which can be examined via the dmesg
10command (perhaps grepping for "rcutorture"). The test is started 10command (perhaps grepping for "torture"). The test is started
11when the module is loaded, and stops when the module is unloaded. 11when the module is loaded, and stops when the module is unloaded.
12 12
13However, actually setting this config option to "y" results in the system 13However, actually setting this config option to "y" results in the system
@@ -35,6 +35,19 @@ stat_interval The number of seconds between output of torture
35 be printed -only- when the module is unloaded, and this 35 be printed -only- when the module is unloaded, and this
36 is the default. 36 is the default.
37 37
38shuffle_interval
39 The number of seconds to keep the test threads affinitied
40 to a particular subset of the CPUs. Used in conjunction
41 with test_no_idle_hz.
42
43test_no_idle_hz Whether or not to test the ability of RCU to operate in
44 a kernel that disables the scheduling-clock interrupt to
45 idle CPUs. Boolean parameter, "1" to test, "0" otherwise.
46
47torture_type The type of RCU to test: "rcu" for the rcu_read_lock()
48 API, "rcu_bh" for the rcu_read_lock_bh() API, and "srcu"
49 for the "srcu_read_lock()" API.
50
38verbose Enable debug printk()s. Default is disabled. 51verbose Enable debug printk()s. Default is disabled.
39 52
40 53
@@ -42,14 +55,14 @@ OUTPUT
42 55
43The statistics output is as follows: 56The statistics output is as follows:
44 57
45 rcutorture: --- Start of test: nreaders=16 stat_interval=0 verbose=0 58 rcu-torture: --- Start of test: nreaders=16 stat_interval=0 verbose=0
46 rcutorture: rtc: 0000000000000000 ver: 1916 tfle: 0 rta: 1916 rtaf: 0 rtf: 1915 59 rcu-torture: rtc: 0000000000000000 ver: 1916 tfle: 0 rta: 1916 rtaf: 0 rtf: 1915
47 rcutorture: Reader Pipe: 1466408 9747 0 0 0 0 0 0 0 0 0 60 rcu-torture: Reader Pipe: 1466408 9747 0 0 0 0 0 0 0 0 0
48 rcutorture: Reader Batch: 1464477 11678 0 0 0 0 0 0 0 0 61 rcu-torture: Reader Batch: 1464477 11678 0 0 0 0 0 0 0 0
49 rcutorture: Free-Block Circulation: 1915 1915 1915 1915 1915 1915 1915 1915 1915 1915 0 62 rcu-torture: Free-Block Circulation: 1915 1915 1915 1915 1915 1915 1915 1915 1915 1915 0
50 rcutorture: --- End of test 63 rcu-torture: --- End of test
51 64
52The command "dmesg | grep rcutorture:" will extract this information on 65The command "dmesg | grep torture:" will extract this information on
53most systems. On more esoteric configurations, it may be necessary to 66most systems. On more esoteric configurations, it may be necessary to
54use other commands to access the output of the printk()s used by 67use other commands to access the output of the printk()s used by
55the RCU torture test. The printk()s use KERN_ALERT, so they should 68the RCU torture test. The printk()s use KERN_ALERT, so they should
@@ -115,8 +128,9 @@ The following script may be used to torture RCU:
115 modprobe rcutorture 128 modprobe rcutorture
116 sleep 100 129 sleep 100
117 rmmod rcutorture 130 rmmod rcutorture
118 dmesg | grep rcutorture: 131 dmesg | grep torture:
119 132
120The output can be manually inspected for the error flag of "!!!". 133The output can be manually inspected for the error flag of "!!!".
121One could of course create a more elaborate script that automatically 134One could of course create a more elaborate script that automatically
122checked for such errors. 135checked for such errors. The "rmmod" command forces a "SUCCESS" or
136"FAILURE" indication to be printk()ed.
diff --git a/Documentation/arm/Samsung-S3C24XX/Overview.txt b/Documentation/arm/Samsung-S3C24XX/Overview.txt
index 8c6ee684174c..3e46d2a31158 100644
--- a/Documentation/arm/Samsung-S3C24XX/Overview.txt
+++ b/Documentation/arm/Samsung-S3C24XX/Overview.txt
@@ -7,11 +7,13 @@ Introduction
7------------ 7------------
8 8
9 The Samsung S3C24XX range of ARM9 System-on-Chip CPUs are supported 9 The Samsung S3C24XX range of ARM9 System-on-Chip CPUs are supported
10 by the 's3c2410' architecture of ARM Linux. Currently the S3C2410 and 10 by the 's3c2410' architecture of ARM Linux. Currently the S3C2410,
11 the S3C2440 are supported CPUs. 11 S3C2440 and S3C2442 devices are supported.
12 12
13 Support for the S3C2400 series is in progress. 13 Support for the S3C2400 series is in progress.
14 14
15 Support for the S3C2412 and S3C2413 CPUs is being merged.
16
15 17
16Configuration 18Configuration
17------------- 19-------------
@@ -43,9 +45,18 @@ Machines
43 45
44 Samsung's own development board, geared for PDA work. 46 Samsung's own development board, geared for PDA work.
45 47
48 Samsung/Aiji SMDK2412
49
50 The S3C2412 version of the SMDK2440.
51
52 Samsung/Aiji SMDK2413
53
54 The S3C2412 version of the SMDK2440.
55
46 Samsung/Meritech SMDK2440 56 Samsung/Meritech SMDK2440
47 57
48 The S3C2440 compatible version of the SMDK2440 58 The S3C2440 compatible version of the SMDK2440, which has the
59 option of an S3C2440 or S3C2442 CPU module.
49 60
50 Thorcom VR1000 61 Thorcom VR1000
51 62
@@ -211,24 +222,6 @@ Port Contributors
211 Lucas Correia Villa Real (S3C2400 port) 222 Lucas Correia Villa Real (S3C2400 port)
212 223
213 224
214Document Changes
215----------------
216
217 05 Sep 2004 - BJD - Added Document Changes section
218 05 Sep 2004 - BJD - Added Klaus Fetscher to list of contributors
219 25 Oct 2004 - BJD - Added Dimitry Andric to list of contributors
220 25 Oct 2004 - BJD - Updated the MTD from the 2.6.9 merge
221 21 Jan 2005 - BJD - Added rx3715, added Shannon to contributors
222 10 Feb 2005 - BJD - Added Guillaume Gourat to contributors
223 02 Mar 2005 - BJD - Added SMDK2440 to list of machines
224 06 Mar 2005 - BJD - Added Christer Weinigel
225 08 Mar 2005 - BJD - Added LCVR to list of people, updated introduction
226 08 Mar 2005 - BJD - Added section on adding machines
227 09 Sep 2005 - BJD - Added section on platform data
228 11 Feb 2006 - BJD - Added I2C, RTC and Watchdog sections
229 11 Feb 2006 - BJD - Added Osiris machine, and S3C2400 information
230
231
232Document Author 225Document Author
233--------------- 226---------------
234 227
diff --git a/Documentation/arm/Samsung-S3C24XX/S3C2412.txt b/Documentation/arm/Samsung-S3C24XX/S3C2412.txt
new file mode 100644
index 000000000000..cb82a7fc7901
--- /dev/null
+++ b/Documentation/arm/Samsung-S3C24XX/S3C2412.txt
@@ -0,0 +1,120 @@
1 S3C2412 ARM Linux Overview
2 ==========================
3
4Introduction
5------------
6
7 The S3C2412 is part of the S3C24XX range of ARM9 System-on-Chip CPUs
8 from Samsung. This part has an ARM926-EJS core, capable of running up
9 to 266MHz (see data-sheet for more information)
10
11
12Clock
13-----
14
15 The core clock code provides a set of clocks to the drivers, and allows
16 for source selection and a number of other features.
17
18
19Power
20-----
21
22 No support for suspend/resume to RAM in the current system.
23
24
25DMA
26---
27
28 No current support for DMA.
29
30
31GPIO
32----
33
34 There is support for setting the GPIO to input/output/special function
35 and reading or writing to them.
36
37
38UART
39----
40
41 The UART hardware is similar to the S3C2440, and is supported by the
42 s3c2410 driver in the drivers/serial directory.
43
44
45NAND
46----
47
48 The NAND hardware is similar to the S3C2440, and is supported by the
49 s3c2410 driver in the drivers/mtd/nand directory.
50
51
52USB Host
53--------
54
55 The USB hardware is similar to the S3C2410, with extended clock source
56 control. The OHCI portion is supported by the ohci-s3c2410 driver, and
57 the clock control selection is supported by the core clock code.
58
59
60USB Device
61----------
62
63 No current support in the kernel
64
65
66IRQs
67----
68
69 All the standard, and external interrupt sources are supported. The
70 extra sub-sources are not yet supported.
71
72
73RTC
74---
75
76 The RTC hardware is similar to the S3C2410, and is supported by the
77 s3c2410-rtc driver.
78
79
80Watchdog
81--------
82
83 The watchdog harware is the same as the S3C2410, and is supported by
84 the s3c2410_wdt driver.
85
86
87MMC/SD/SDIO
88-----------
89
90 No current support for the MMC/SD/SDIO block.
91
92IIC
93---
94
95 The IIC hardware is the same as the S3C2410, and is supported by the
96 i2c-s3c24xx driver.
97
98
99IIS
100---
101
102 No current support for the IIS interface.
103
104
105SPI
106---
107
108 No current support for the SPI interfaces.
109
110
111ATA
112---
113
114 No current support for the on-board ATA block.
115
116
117Document Author
118---------------
119
120Ben Dooks, (c) 2006 Simtec Electronics
diff --git a/Documentation/arm/Samsung-S3C24XX/S3C2413.txt b/Documentation/arm/Samsung-S3C24XX/S3C2413.txt
new file mode 100644
index 000000000000..ab2a88858f12
--- /dev/null
+++ b/Documentation/arm/Samsung-S3C24XX/S3C2413.txt
@@ -0,0 +1,21 @@
1 S3C2413 ARM Linux Overview
2 ==========================
3
4Introduction
5------------
6
7 The S3C2413 is an extended version of the S3C2412, with an camera
8 interface and mobile DDR memory support. See the S3C2412 support
9 documentation for more information.
10
11
12Camera Interface
13---------------
14
15 This block is currently not supported.
16
17
18Document Author
19---------------
20
21Ben Dooks, (c) 2006 Simtec Electronics
diff --git a/Documentation/atomic_ops.txt b/Documentation/atomic_ops.txt
index 23a1c2402bcc..2a63d5662a93 100644
--- a/Documentation/atomic_ops.txt
+++ b/Documentation/atomic_ops.txt
@@ -157,13 +157,13 @@ For example, smp_mb__before_atomic_dec() can be used like so:
157 smp_mb__before_atomic_dec(); 157 smp_mb__before_atomic_dec();
158 atomic_dec(&obj->ref_count); 158 atomic_dec(&obj->ref_count);
159 159
160It makes sure that all memory operations preceeding the atomic_dec() 160It makes sure that all memory operations preceding the atomic_dec()
161call are strongly ordered with respect to the atomic counter 161call are strongly ordered with respect to the atomic counter
162operation. In the above example, it guarentees that the assignment of 162operation. In the above example, it guarantees that the assignment of
163"1" to obj->dead will be globally visible to other cpus before the 163"1" to obj->dead will be globally visible to other cpus before the
164atomic counter decrement. 164atomic counter decrement.
165 165
166Without the explicitl smp_mb__before_atomic_dec() call, the 166Without the explicit smp_mb__before_atomic_dec() call, the
167implementation could legally allow the atomic counter update visible 167implementation could legally allow the atomic counter update visible
168to other cpus before the "obj->dead = 1;" assignment. 168to other cpus before the "obj->dead = 1;" assignment.
169 169
@@ -173,11 +173,11 @@ ordering with respect to memory operations after an atomic_dec() call
173(smp_mb__{before,after}_atomic_inc()). 173(smp_mb__{before,after}_atomic_inc()).
174 174
175A missing memory barrier in the cases where they are required by the 175A missing memory barrier in the cases where they are required by the
176atomic_t implementation above can have disasterous results. Here is 176atomic_t implementation above can have disastrous results. Here is
177an example, which follows a pattern occuring frequently in the Linux 177an example, which follows a pattern occurring frequently in the Linux
178kernel. It is the use of atomic counters to implement reference 178kernel. It is the use of atomic counters to implement reference
179counting, and it works such that once the counter falls to zero it can 179counting, and it works such that once the counter falls to zero it can
180be guarenteed that no other entity can be accessing the object: 180be guaranteed that no other entity can be accessing the object:
181 181
182static void obj_list_add(struct obj *obj) 182static void obj_list_add(struct obj *obj)
183{ 183{
@@ -291,9 +291,9 @@ to the size of an "unsigned long" C data type, and are least of that
291size. The endianness of the bits within each "unsigned long" are the 291size. The endianness of the bits within each "unsigned long" are the
292native endianness of the cpu. 292native endianness of the cpu.
293 293
294 void set_bit(unsigned long nr, volatils unsigned long *addr); 294 void set_bit(unsigned long nr, volatile unsigned long *addr);
295 void clear_bit(unsigned long nr, volatils unsigned long *addr); 295 void clear_bit(unsigned long nr, volatile unsigned long *addr);
296 void change_bit(unsigned long nr, volatils unsigned long *addr); 296 void change_bit(unsigned long nr, volatile unsigned long *addr);
297 297
298These routines set, clear, and change, respectively, the bit number 298These routines set, clear, and change, respectively, the bit number
299indicated by "nr" on the bit mask pointed to by "ADDR". 299indicated by "nr" on the bit mask pointed to by "ADDR".
@@ -301,9 +301,9 @@ indicated by "nr" on the bit mask pointed to by "ADDR".
301They must execute atomically, yet there are no implicit memory barrier 301They must execute atomically, yet there are no implicit memory barrier
302semantics required of these interfaces. 302semantics required of these interfaces.
303 303
304 int test_and_set_bit(unsigned long nr, volatils unsigned long *addr); 304 int test_and_set_bit(unsigned long nr, volatile unsigned long *addr);
305 int test_and_clear_bit(unsigned long nr, volatils unsigned long *addr); 305 int test_and_clear_bit(unsigned long nr, volatile unsigned long *addr);
306 int test_and_change_bit(unsigned long nr, volatils unsigned long *addr); 306 int test_and_change_bit(unsigned long nr, volatile unsigned long *addr);
307 307
308Like the above, except that these routines return a boolean which 308Like the above, except that these routines return a boolean which
309indicates whether the changed bit was set _BEFORE_ the atomic bit 309indicates whether the changed bit was set _BEFORE_ the atomic bit
@@ -335,7 +335,7 @@ subsequent memory operation is made visible. For example:
335 /* ... */; 335 /* ... */;
336 obj->killed = 1; 336 obj->killed = 1;
337 337
338The implementation of test_and_set_bit() must guarentee that 338The implementation of test_and_set_bit() must guarantee that
339"obj->dead = 1;" is visible to cpus before the atomic memory operation 339"obj->dead = 1;" is visible to cpus before the atomic memory operation
340done by test_and_set_bit() becomes visible. Likewise, the atomic 340done by test_and_set_bit() becomes visible. Likewise, the atomic
341memory operation done by test_and_set_bit() must become visible before 341memory operation done by test_and_set_bit() must become visible before
@@ -474,7 +474,7 @@ Now, as far as memory barriers go, as long as spin_lock()
474strictly orders all subsequent memory operations (including 474strictly orders all subsequent memory operations (including
475the cas()) with respect to itself, things will be fine. 475the cas()) with respect to itself, things will be fine.
476 476
477Said another way, _atomic_dec_and_lock() must guarentee that 477Said another way, _atomic_dec_and_lock() must guarantee that
478a counter dropping to zero is never made visible before the 478a counter dropping to zero is never made visible before the
479spinlock being acquired. 479spinlock being acquired.
480 480
diff --git a/Documentation/driver-model/overview.txt b/Documentation/driver-model/overview.txt
index ac4a7a737e43..2050c9ffc629 100644
--- a/Documentation/driver-model/overview.txt
+++ b/Documentation/driver-model/overview.txt
@@ -18,7 +18,7 @@ Traditional driver models implemented some sort of tree-like structure
18(sometimes just a list) for the devices they control. There wasn't any 18(sometimes just a list) for the devices they control. There wasn't any
19uniformity across the different bus types. 19uniformity across the different bus types.
20 20
21The current driver model provides a comon, uniform data model for describing 21The current driver model provides a common, uniform data model for describing
22a bus and the devices that can appear under the bus. The unified bus 22a bus and the devices that can appear under the bus. The unified bus
23model includes a set of common attributes which all busses carry, and a set 23model includes a set of common attributes which all busses carry, and a set
24of common callbacks, such as device discovery during bus probing, bus 24of common callbacks, such as device discovery during bus probing, bus
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt
index ddfd77029597..1cbbb8e28999 100644
--- a/Documentation/feature-removal-schedule.txt
+++ b/Documentation/feature-removal-schedule.txt
@@ -121,16 +121,6 @@ Who: NeilBrown <neilb@suse.de>
121 121
122--------------------------- 122---------------------------
123 123
124What: au1x00_uart driver
125When: January 2006
126Why: The 8250 serial driver now has the ability to deal with the differences
127 between the standard 8250 family of UARTs and their slightly strange
128 brother on Alchemy SOCs. The loss of features is not considered an
129 issue.
130Who: Ralf Baechle <ralf@linux-mips.org>
131
132---------------------------
133
134What: eepro100 network driver 124What: eepro100 network driver
135When: January 2007 125When: January 2007
136Why: replaced by the e100 driver 126Why: replaced by the e100 driver
@@ -166,6 +156,16 @@ Who: Jean Delvare <khali@linux-fr.org>
166 156
167--------------------------- 157---------------------------
168 158
159What: Unused EXPORT_SYMBOL/EXPORT_SYMBOL_GPL exports
160 (temporary transition config option provided until then)
161 The transition config option will also be removed at the same time.
162When: before 2.6.19
163Why: Unused symbols are both increasing the size of the kernel binary
164 and are often a sign of "wrong API"
165Who: Arjan van de Ven <arjan@linux.intel.com>
166
167---------------------------
168
169What: remove EXPORT_SYMBOL(tasklist_lock) 169What: remove EXPORT_SYMBOL(tasklist_lock)
170When: August 2006 170When: August 2006
171Files: kernel/fork.c 171Files: kernel/fork.c
@@ -213,3 +213,47 @@ Why: The interface no longer has any callers left in the kernel. It
213Who: Nick Piggin <npiggin@suse.de> 213Who: Nick Piggin <npiggin@suse.de>
214 214
215--------------------------- 215---------------------------
216
217What: Support for the MIPS EV96100 evaluation board
218When: September 2006
219Why: Does no longer build since at least November 15, 2003, apparently
220 no userbase left.
221Who: Ralf Baechle <ralf@linux-mips.org>
222
223---------------------------
224
225What: Support for the Momentum / PMC-Sierra Jaguar ATX evaluation board
226When: September 2006
227Why: Does no longer build since quite some time, and was never popular,
228 due to the platform being replaced by successor models. Apparently
229 no user base left. It also is one of the last users of
230 WANT_PAGE_VIRTUAL.
231Who: Ralf Baechle <ralf@linux-mips.org>
232
233---------------------------
234
235What: Support for the Momentum Ocelot, Ocelot 3, Ocelot C and Ocelot G
236When: September 2006
237Why: Some do no longer build and apparently there is no user base left
238 for these platforms.
239Who: Ralf Baechle <ralf@linux-mips.org>
240
241---------------------------
242
243What: Support for MIPS Technologies' Altas and SEAD evaluation board
244When: September 2006
245Why: Some do no longer build and apparently there is no user base left
246 for these platforms. Hardware out of production since several years.
247Who: Ralf Baechle <ralf@linux-mips.org>
248
249---------------------------
250
251What: Support for the IT8172-based platforms, ITE 8172G and Globespan IVR
252When: September 2006
253Why: Code does no longer build since at least 2.6.0, apparently there is
254 no user base left for these platforms. Hardware out of production
255 since several years and hardly a trace of the manufacturer left on
256 the net.
257Who: Ralf Baechle <ralf@linux-mips.org>
258
259---------------------------
diff --git a/Documentation/kdump/gdbmacros.txt b/Documentation/kdump/gdbmacros.txt
index dcf5580380ab..9b9b454b048a 100644
--- a/Documentation/kdump/gdbmacros.txt
+++ b/Documentation/kdump/gdbmacros.txt
@@ -175,7 +175,7 @@ end
175document trapinfo 175document trapinfo
176 Run info threads and lookup pid of thread #1 176 Run info threads and lookup pid of thread #1
177 'trapinfo <pid>' will tell you by which trap & possibly 177 'trapinfo <pid>' will tell you by which trap & possibly
178 addresthe kernel paniced. 178 address the kernel panicked.
179end 179end
180 180
181 181
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index bf5d2cd6a56e..86e9282d1c20 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -1665,6 +1665,10 @@ running once the system is up.
1665 usbhid.mousepoll= 1665 usbhid.mousepoll=
1666 [USBHID] The interval which mice are to be polled at. 1666 [USBHID] The interval which mice are to be polled at.
1667 1667
1668 vdso= [IA-32]
1669 vdso=1: enable VDSO (default)
1670 vdso=0: disable VDSO mapping
1671
1668 video= [FB] Frame buffer configuration 1672 video= [FB] Frame buffer configuration
1669 See Documentation/fb/modedb.txt. 1673 See Documentation/fb/modedb.txt.
1670 1674
@@ -1681,9 +1685,14 @@ running once the system is up.
1681 decrease the size and leave more room for directly 1685 decrease the size and leave more room for directly
1682 mapped kernel RAM. 1686 mapped kernel RAM.
1683 1687
1684 vmhalt= [KNL,S390] 1688 vmhalt= [KNL,S390] Perform z/VM CP command after system halt.
1689 Format: <command>
1690
1691 vmpanic= [KNL,S390] Perform z/VM CP command after kernel panic.
1692 Format: <command>
1685 1693
1686 vmpoff= [KNL,S390] 1694 vmpoff= [KNL,S390] Perform z/VM CP command after power off.
1695 Format: <command>
1687 1696
1688 waveartist= [HW,OSS] 1697 waveartist= [HW,OSS]
1689 Format: <io>,<irq>,<dma>,<dma2> 1698 Format: <io>,<irq>,<dma>,<dma2>
diff --git a/Documentation/keys-request-key.txt b/Documentation/keys-request-key.txt
index 22488d791168..c1f64fdf84cb 100644
--- a/Documentation/keys-request-key.txt
+++ b/Documentation/keys-request-key.txt
@@ -3,16 +3,23 @@
3 =================== 3 ===================
4 4
5The key request service is part of the key retention service (refer to 5The key request service is part of the key retention service (refer to
6Documentation/keys.txt). This document explains more fully how that the 6Documentation/keys.txt). This document explains more fully how the requesting
7requesting algorithm works. 7algorithm works.
8 8
9The process starts by either the kernel requesting a service by calling 9The process starts by either the kernel requesting a service by calling
10request_key(): 10request_key*():
11 11
12 struct key *request_key(const struct key_type *type, 12 struct key *request_key(const struct key_type *type,
13 const char *description, 13 const char *description,
14 const char *callout_string); 14 const char *callout_string);
15 15
16or:
17
18 struct key *request_key_with_auxdata(const struct key_type *type,
19 const char *description,
20 const char *callout_string,
21 void *aux);
22
16Or by userspace invoking the request_key system call: 23Or by userspace invoking the request_key system call:
17 24
18 key_serial_t request_key(const char *type, 25 key_serial_t request_key(const char *type,
@@ -20,16 +27,26 @@ Or by userspace invoking the request_key system call:
20 const char *callout_info, 27 const char *callout_info,
21 key_serial_t dest_keyring); 28 key_serial_t dest_keyring);
22 29
23The main difference between the two access points is that the in-kernel 30The main difference between the access points is that the in-kernel interface
24interface does not need to link the key to a keyring to prevent it from being 31does not need to link the key to a keyring to prevent it from being immediately
25immediately destroyed. The kernel interface returns a pointer directly to the 32destroyed. The kernel interface returns a pointer directly to the key, and
26key, and it's up to the caller to destroy the key. 33it's up to the caller to destroy the key.
34
35The request_key_with_auxdata() call is like the in-kernel request_key() call,
36except that it permits auxiliary data to be passed to the upcaller (the default
37is NULL). This is only useful for those key types that define their own upcall
38mechanism rather than using /sbin/request-key.
27 39
28The userspace interface links the key to a keyring associated with the process 40The userspace interface links the key to a keyring associated with the process
29to prevent the key from going away, and returns the serial number of the key to 41to prevent the key from going away, and returns the serial number of the key to
30the caller. 42the caller.
31 43
32 44
45The following example assumes that the key types involved don't define their
46own upcall mechanisms. If they do, then those should be substituted for the
47forking and execution of /sbin/request-key.
48
49
33=========== 50===========
34THE PROCESS 51THE PROCESS
35=========== 52===========
@@ -40,8 +57,8 @@ A request proceeds in the following manner:
40 interface]. 57 interface].
41 58
42 (2) request_key() searches the process's subscribed keyrings to see if there's 59 (2) request_key() searches the process's subscribed keyrings to see if there's
43 a suitable key there. If there is, it returns the key. If there isn't, and 60 a suitable key there. If there is, it returns the key. If there isn't,
44 callout_info is not set, an error is returned. Otherwise the process 61 and callout_info is not set, an error is returned. Otherwise the process
45 proceeds to the next step. 62 proceeds to the next step.
46 63
47 (3) request_key() sees that A doesn't have the desired key yet, so it creates 64 (3) request_key() sees that A doesn't have the desired key yet, so it creates
@@ -62,7 +79,7 @@ A request proceeds in the following manner:
62 instantiation. 79 instantiation.
63 80
64 (7) The program may want to access another key from A's context (say a 81 (7) The program may want to access another key from A's context (say a
65 Kerberos TGT key). It just requests the appropriate key, and the keyring 82 Kerberos TGT key). It just requests the appropriate key, and the keyring
66 search notes that the session keyring has auth key V in its bottom level. 83 search notes that the session keyring has auth key V in its bottom level.
67 84
68 This will permit it to then search the keyrings of process A with the 85 This will permit it to then search the keyrings of process A with the
@@ -79,10 +96,11 @@ A request proceeds in the following manner:
79(10) The program then exits 0 and request_key() deletes key V and returns key 96(10) The program then exits 0 and request_key() deletes key V and returns key
80 U to the caller. 97 U to the caller.
81 98
82This also extends further. If key W (step 7 above) didn't exist, key W would be 99This also extends further. If key W (step 7 above) didn't exist, key W would
83created uninstantiated, another auth key (X) would be created (as per step 3) 100be created uninstantiated, another auth key (X) would be created (as per step
84and another copy of /sbin/request-key spawned (as per step 4); but the context 1013) and another copy of /sbin/request-key spawned (as per step 4); but the
85specified by auth key X will still be process A, as it was in auth key V. 102context specified by auth key X will still be process A, as it was in auth key
103V.
86 104
87This is because process A's keyrings can't simply be attached to 105This is because process A's keyrings can't simply be attached to
88/sbin/request-key at the appropriate places because (a) execve will discard two 106/sbin/request-key at the appropriate places because (a) execve will discard two
@@ -118,17 +136,17 @@ A search of any particular keyring proceeds in the following fashion:
118 136
119 (2) It considers all the non-keyring keys within that keyring and, if any key 137 (2) It considers all the non-keyring keys within that keyring and, if any key
120 matches the criteria specified, calls key_permission(SEARCH) on it to see 138 matches the criteria specified, calls key_permission(SEARCH) on it to see
121 if the key is allowed to be found. If it is, that key is returned; if 139 if the key is allowed to be found. If it is, that key is returned; if
122 not, the search continues, and the error code is retained if of higher 140 not, the search continues, and the error code is retained if of higher
123 priority than the one currently set. 141 priority than the one currently set.
124 142
125 (3) It then considers all the keyring-type keys in the keyring it's currently 143 (3) It then considers all the keyring-type keys in the keyring it's currently
126 searching. It calls key_permission(SEARCH) on each keyring, and if this 144 searching. It calls key_permission(SEARCH) on each keyring, and if this
127 grants permission, it recurses, executing steps (2) and (3) on that 145 grants permission, it recurses, executing steps (2) and (3) on that
128 keyring. 146 keyring.
129 147
130The process stops immediately a valid key is found with permission granted to 148The process stops immediately a valid key is found with permission granted to
131use it. Any error from a previous match attempt is discarded and the key is 149use it. Any error from a previous match attempt is discarded and the key is
132returned. 150returned.
133 151
134When search_process_keyrings() is invoked, it performs the following searches 152When search_process_keyrings() is invoked, it performs the following searches
@@ -153,7 +171,7 @@ The moment one succeeds, all pending errors are discarded and the found key is
153returned. 171returned.
154 172
155Only if all these fail does the whole thing fail with the highest priority 173Only if all these fail does the whole thing fail with the highest priority
156error. Note that several errors may have come from LSM. 174error. Note that several errors may have come from LSM.
157 175
158The error priority is: 176The error priority is:
159 177
diff --git a/Documentation/keys.txt b/Documentation/keys.txt
index 61c0fad2fe2f..e373f0212843 100644
--- a/Documentation/keys.txt
+++ b/Documentation/keys.txt
@@ -780,6 +780,17 @@ payload contents" for more information.
780 See also Documentation/keys-request-key.txt. 780 See also Documentation/keys-request-key.txt.
781 781
782 782
783(*) To search for a key, passing auxiliary data to the upcaller, call:
784
785 struct key *request_key_with_auxdata(const struct key_type *type,
786 const char *description,
787 const char *callout_string,
788 void *aux);
789
790 This is identical to request_key(), except that the auxiliary data is
791 passed to the key_type->request_key() op if it exists.
792
793
783(*) When it is no longer required, the key should be released using: 794(*) When it is no longer required, the key should be released using:
784 795
785 void key_put(struct key *key); 796 void key_put(struct key *key);
@@ -1031,6 +1042,24 @@ The structure has a number of fields, some of which are mandatory:
1031 as might happen when the userspace buffer is accessed. 1042 as might happen when the userspace buffer is accessed.
1032 1043
1033 1044
1045 (*) int (*request_key)(struct key *key, struct key *authkey, const char *op,
1046 void *aux);
1047
1048 This method is optional. If provided, request_key() and
1049 request_key_with_auxdata() will invoke this function rather than
1050 upcalling to /sbin/request-key to operate upon a key of this type.
1051
1052 The aux parameter is as passed to request_key_with_auxdata() or is NULL
1053 otherwise. Also passed are the key to be operated upon, the
1054 authorisation key for this operation and the operation type (currently
1055 only "create").
1056
1057 This function should return only when the upcall is complete. Upon return
1058 the authorisation key will be revoked, and the target key will be
1059 negatively instantiated if it is still uninstantiated. The error will be
1060 returned to the caller of request_key*().
1061
1062
1034============================ 1063============================
1035REQUEST-KEY CALLBACK SERVICE 1064REQUEST-KEY CALLBACK SERVICE
1036============================ 1065============================
diff --git a/Documentation/pi-futex.txt b/Documentation/pi-futex.txt
new file mode 100644
index 000000000000..5d61dacd21f6
--- /dev/null
+++ b/Documentation/pi-futex.txt
@@ -0,0 +1,121 @@
1Lightweight PI-futexes
2----------------------
3
4We are calling them lightweight for 3 reasons:
5
6 - in the user-space fastpath a PI-enabled futex involves no kernel work
7 (or any other PI complexity) at all. No registration, no extra kernel
8 calls - just pure fast atomic ops in userspace.
9
10 - even in the slowpath, the system call and scheduling pattern is very
11 similar to normal futexes.
12
13 - the in-kernel PI implementation is streamlined around the mutex
14 abstraction, with strict rules that keep the implementation
15 relatively simple: only a single owner may own a lock (i.e. no
16 read-write lock support), only the owner may unlock a lock, no
17 recursive locking, etc.
18
19Priority Inheritance - why?
20---------------------------
21
22The short reply: user-space PI helps achieving/improving determinism for
23user-space applications. In the best-case, it can help achieve
24determinism and well-bound latencies. Even in the worst-case, PI will
25improve the statistical distribution of locking related application
26delays.
27
28The longer reply:
29-----------------
30
31Firstly, sharing locks between multiple tasks is a common programming
32technique that often cannot be replaced with lockless algorithms. As we
33can see it in the kernel [which is a quite complex program in itself],
34lockless structures are rather the exception than the norm - the current
35ratio of lockless vs. locky code for shared data structures is somewhere
36between 1:10 and 1:100. Lockless is hard, and the complexity of lockless
37algorithms often endangers to ability to do robust reviews of said code.
38I.e. critical RT apps often choose lock structures to protect critical
39data structures, instead of lockless algorithms. Furthermore, there are
40cases (like shared hardware, or other resource limits) where lockless
41access is mathematically impossible.
42
43Media players (such as Jack) are an example of reasonable application
44design with multiple tasks (with multiple priority levels) sharing
45short-held locks: for example, a highprio audio playback thread is
46combined with medium-prio construct-audio-data threads and low-prio
47display-colory-stuff threads. Add video and decoding to the mix and
48we've got even more priority levels.
49
50So once we accept that synchronization objects (locks) are an
51unavoidable fact of life, and once we accept that multi-task userspace
52apps have a very fair expectation of being able to use locks, we've got
53to think about how to offer the option of a deterministic locking
54implementation to user-space.
55
56Most of the technical counter-arguments against doing priority
57inheritance only apply to kernel-space locks. But user-space locks are
58different, there we cannot disable interrupts or make the task
59non-preemptible in a critical section, so the 'use spinlocks' argument
60does not apply (user-space spinlocks have the same priority inversion
61problems as other user-space locking constructs). Fact is, pretty much
62the only technique that currently enables good determinism for userspace
63locks (such as futex-based pthread mutexes) is priority inheritance:
64
65Currently (without PI), if a high-prio and a low-prio task shares a lock
66[this is a quite common scenario for most non-trivial RT applications],
67even if all critical sections are coded carefully to be deterministic
68(i.e. all critical sections are short in duration and only execute a
69limited number of instructions), the kernel cannot guarantee any
70deterministic execution of the high-prio task: any medium-priority task
71could preempt the low-prio task while it holds the shared lock and
72executes the critical section, and could delay it indefinitely.
73
74Implementation:
75---------------
76
77As mentioned before, the userspace fastpath of PI-enabled pthread
78mutexes involves no kernel work at all - they behave quite similarly to
79normal futex-based locks: a 0 value means unlocked, and a value==TID
80means locked. (This is the same method as used by list-based robust
81futexes.) Userspace uses atomic ops to lock/unlock these mutexes without
82entering the kernel.
83
84To handle the slowpath, we have added two new futex ops:
85
86 FUTEX_LOCK_PI
87 FUTEX_UNLOCK_PI
88
89If the lock-acquire fastpath fails, [i.e. an atomic transition from 0 to
90TID fails], then FUTEX_LOCK_PI is called. The kernel does all the
91remaining work: if there is no futex-queue attached to the futex address
92yet then the code looks up the task that owns the futex [it has put its
93own TID into the futex value], and attaches a 'PI state' structure to
94the futex-queue. The pi_state includes an rt-mutex, which is a PI-aware,
95kernel-based synchronization object. The 'other' task is made the owner
96of the rt-mutex, and the FUTEX_WAITERS bit is atomically set in the
97futex value. Then this task tries to lock the rt-mutex, on which it
98blocks. Once it returns, it has the mutex acquired, and it sets the
99futex value to its own TID and returns. Userspace has no other work to
100perform - it now owns the lock, and futex value contains
101FUTEX_WAITERS|TID.
102
103If the unlock side fastpath succeeds, [i.e. userspace manages to do a
104TID -> 0 atomic transition of the futex value], then no kernel work is
105triggered.
106
107If the unlock fastpath fails (because the FUTEX_WAITERS bit is set),
108then FUTEX_UNLOCK_PI is called, and the kernel unlocks the futex on the
109behalf of userspace - and it also unlocks the attached
110pi_state->rt_mutex and thus wakes up any potential waiters.
111
112Note that under this approach, contrary to previous PI-futex approaches,
113there is no prior 'registration' of a PI-futex. [which is not quite
114possible anyway, due to existing ABI properties of pthread mutexes.]
115
116Also, under this scheme, 'robustness' and 'PI' are two orthogonal
117properties of futexes, and all four combinations are possible: futex,
118robust-futex, PI-futex, robust+PI-futex.
119
120More details about priority inheritance can be found in
121Documentation/rtmutex.txt.
diff --git a/Documentation/robust-futexes.txt b/Documentation/robust-futexes.txt
index df82d75245a0..76e8064b8c3a 100644
--- a/Documentation/robust-futexes.txt
+++ b/Documentation/robust-futexes.txt
@@ -95,7 +95,7 @@ comparison. If the thread has registered a list, then normally the list
95is empty. If the thread/process crashed or terminated in some incorrect 95is empty. If the thread/process crashed or terminated in some incorrect
96way then the list might be non-empty: in this case the kernel carefully 96way then the list might be non-empty: in this case the kernel carefully
97walks the list [not trusting it], and marks all locks that are owned by 97walks the list [not trusting it], and marks all locks that are owned by
98this thread with the FUTEX_OWNER_DEAD bit, and wakes up one waiter (if 98this thread with the FUTEX_OWNER_DIED bit, and wakes up one waiter (if
99any). 99any).
100 100
101The list is guaranteed to be private and per-thread at do_exit() time, 101The list is guaranteed to be private and per-thread at do_exit() time,
diff --git a/Documentation/rt-mutex-design.txt b/Documentation/rt-mutex-design.txt
new file mode 100644
index 000000000000..c472ffacc2f6
--- /dev/null
+++ b/Documentation/rt-mutex-design.txt
@@ -0,0 +1,781 @@
1#
2# Copyright (c) 2006 Steven Rostedt
3# Licensed under the GNU Free Documentation License, Version 1.2
4#
5
6RT-mutex implementation design
7------------------------------
8
9This document tries to describe the design of the rtmutex.c implementation.
10It doesn't describe the reasons why rtmutex.c exists. For that please see
11Documentation/rt-mutex.txt. Although this document does explain problems
12that happen without this code, but that is in the concept to understand
13what the code actually is doing.
14
15The goal of this document is to help others understand the priority
16inheritance (PI) algorithm that is used, as well as reasons for the
17decisions that were made to implement PI in the manner that was done.
18
19
20Unbounded Priority Inversion
21----------------------------
22
23Priority inversion is when a lower priority process executes while a higher
24priority process wants to run. This happens for several reasons, and
25most of the time it can't be helped. Anytime a high priority process wants
26to use a resource that a lower priority process has (a mutex for example),
27the high priority process must wait until the lower priority process is done
28with the resource. This is a priority inversion. What we want to prevent
29is something called unbounded priority inversion. That is when the high
30priority process is prevented from running by a lower priority process for
31an undetermined amount of time.
32
33The classic example of unbounded priority inversion is were you have three
34processes, let's call them processes A, B, and C, where A is the highest
35priority process, C is the lowest, and B is in between. A tries to grab a lock
36that C owns and must wait and lets C run to release the lock. But in the
37meantime, B executes, and since B is of a higher priority than C, it preempts C,
38but by doing so, it is in fact preempting A which is a higher priority process.
39Now there's no way of knowing how long A will be sleeping waiting for C
40to release the lock, because for all we know, B is a CPU hog and will
41never give C a chance to release the lock. This is called unbounded priority
42inversion.
43
44Here's a little ASCII art to show the problem.
45
46 grab lock L1 (owned by C)
47 |
48A ---+
49 C preempted by B
50 |
51C +----+
52
53B +-------->
54 B now keeps A from running.
55
56
57Priority Inheritance (PI)
58-------------------------
59
60There are several ways to solve this issue, but other ways are out of scope
61for this document. Here we only discuss PI.
62
63PI is where a process inherits the priority of another process if the other
64process blocks on a lock owned by the current process. To make this easier
65to understand, let's use the previous example, with processes A, B, and C again.
66
67This time, when A blocks on the lock owned by C, C would inherit the priority
68of A. So now if B becomes runnable, it would not preempt C, since C now has
69the high priority of A. As soon as C releases the lock, it loses its
70inherited priority, and A then can continue with the resource that C had.
71
72Terminology
73-----------
74
75Here I explain some terminology that is used in this document to help describe
76the design that is used to implement PI.
77
78PI chain - The PI chain is an ordered series of locks and processes that cause
79 processes to inherit priorities from a previous process that is
80 blocked on one of its locks. This is described in more detail
81 later in this document.
82
83mutex - In this document, to differentiate from locks that implement
84 PI and spin locks that are used in the PI code, from now on
85 the PI locks will be called a mutex.
86
87lock - In this document from now on, I will use the term lock when
88 referring to spin locks that are used to protect parts of the PI
89 algorithm. These locks disable preemption for UP (when
90 CONFIG_PREEMPT is enabled) and on SMP prevents multiple CPUs from
91 entering critical sections simultaneously.
92
93spin lock - Same as lock above.
94
95waiter - A waiter is a struct that is stored on the stack of a blocked
96 process. Since the scope of the waiter is within the code for
97 a process being blocked on the mutex, it is fine to allocate
98 the waiter on the process's stack (local variable). This
99 structure holds a pointer to the task, as well as the mutex that
100 the task is blocked on. It also has the plist node structures to
101 place the task in the waiter_list of a mutex as well as the
102 pi_list of a mutex owner task (described below).
103
104 waiter is sometimes used in reference to the task that is waiting
105 on a mutex. This is the same as waiter->task.
106
107waiters - A list of processes that are blocked on a mutex.
108
109top waiter - The highest priority process waiting on a specific mutex.
110
111top pi waiter - The highest priority process waiting on one of the mutexes
112 that a specific process owns.
113
114Note: task and process are used interchangeably in this document, mostly to
115 differentiate between two processes that are being described together.
116
117
118PI chain
119--------
120
121The PI chain is a list of processes and mutexes that may cause priority
122inheritance to take place. Multiple chains may converge, but a chain
123would never diverge, since a process can't be blocked on more than one
124mutex at a time.
125
126Example:
127
128 Process: A, B, C, D, E
129 Mutexes: L1, L2, L3, L4
130
131 A owns: L1
132 B blocked on L1
133 B owns L2
134 C blocked on L2
135 C owns L3
136 D blocked on L3
137 D owns L4
138 E blocked on L4
139
140The chain would be:
141
142 E->L4->D->L3->C->L2->B->L1->A
143
144To show where two chains merge, we could add another process F and
145another mutex L5 where B owns L5 and F is blocked on mutex L5.
146
147The chain for F would be:
148
149 F->L5->B->L1->A
150
151Since a process may own more than one mutex, but never be blocked on more than
152one, the chains merge.
153
154Here we show both chains:
155
156 E->L4->D->L3->C->L2-+
157 |
158 +->B->L1->A
159 |
160 F->L5-+
161
162For PI to work, the processes at the right end of these chains (or we may
163also call it the Top of the chain) must be equal to or higher in priority
164than the processes to the left or below in the chain.
165
166Also since a mutex may have more than one process blocked on it, we can
167have multiple chains merge at mutexes. If we add another process G that is
168blocked on mutex L2:
169
170 G->L2->B->L1->A
171
172And once again, to show how this can grow I will show the merging chains
173again.
174
175 E->L4->D->L3->C-+
176 +->L2-+
177 | |
178 G-+ +->B->L1->A
179 |
180 F->L5-+
181
182
183Plist
184-----
185
186Before I go further and talk about how the PI chain is stored through lists
187on both mutexes and processes, I'll explain the plist. This is similar to
188the struct list_head functionality that is already in the kernel.
189The implementation of plist is out of scope for this document, but it is
190very important to understand what it does.
191
192There are a few differences between plist and list, the most important one
193being that plist is a priority sorted linked list. This means that the
194priorities of the plist are sorted, such that it takes O(1) to retrieve the
195highest priority item in the list. Obviously this is useful to store processes
196based on their priorities.
197
198Another difference, which is important for implementation, is that, unlike
199list, the head of the list is a different element than the nodes of a list.
200So the head of the list is declared as struct plist_head and nodes that will
201be added to the list are declared as struct plist_node.
202
203
204Mutex Waiter List
205-----------------
206
207Every mutex keeps track of all the waiters that are blocked on itself. The mutex
208has a plist to store these waiters by priority. This list is protected by
209a spin lock that is located in the struct of the mutex. This lock is called
210wait_lock. Since the modification of the waiter list is never done in
211interrupt context, the wait_lock can be taken without disabling interrupts.
212
213
214Task PI List
215------------
216
217To keep track of the PI chains, each process has its own PI list. This is
218a list of all top waiters of the mutexes that are owned by the process.
219Note that this list only holds the top waiters and not all waiters that are
220blocked on mutexes owned by the process.
221
222The top of the task's PI list is always the highest priority task that
223is waiting on a mutex that is owned by the task. So if the task has
224inherited a priority, it will always be the priority of the task that is
225at the top of this list.
226
227This list is stored in the task structure of a process as a plist called
228pi_list. This list is protected by a spin lock also in the task structure,
229called pi_lock. This lock may also be taken in interrupt context, so when
230locking the pi_lock, interrupts must be disabled.
231
232
233Depth of the PI Chain
234---------------------
235
236The maximum depth of the PI chain is not dynamic, and could actually be
237defined. But is very complex to figure it out, since it depends on all
238the nesting of mutexes. Let's look at the example where we have 3 mutexes,
239L1, L2, and L3, and four separate functions func1, func2, func3 and func4.
240The following shows a locking order of L1->L2->L3, but may not actually
241be directly nested that way.
242
243void func1(void)
244{
245 mutex_lock(L1);
246
247 /* do anything */
248
249 mutex_unlock(L1);
250}
251
252void func2(void)
253{
254 mutex_lock(L1);
255 mutex_lock(L2);
256
257 /* do something */
258
259 mutex_unlock(L2);
260 mutex_unlock(L1);
261}
262
263void func3(void)
264{
265 mutex_lock(L2);
266 mutex_lock(L3);
267
268 /* do something else */
269
270 mutex_unlock(L3);
271 mutex_unlock(L2);
272}
273
274void func4(void)
275{
276 mutex_lock(L3);
277
278 /* do something again */
279
280 mutex_unlock(L3);
281}
282
283Now we add 4 processes that run each of these functions separately.
284Processes A, B, C, and D which run functions func1, func2, func3 and func4
285respectively, and such that D runs first and A last. With D being preempted
286in func4 in the "do something again" area, we have a locking that follows:
287
288D owns L3
289 C blocked on L3
290 C owns L2
291 B blocked on L2
292 B owns L1
293 A blocked on L1
294
295And thus we have the chain A->L1->B->L2->C->L3->D.
296
297This gives us a PI depth of 4 (four processes), but looking at any of the
298functions individually, it seems as though they only have at most a locking
299depth of two. So, although the locking depth is defined at compile time,
300it still is very difficult to find the possibilities of that depth.
301
302Now since mutexes can be defined by user-land applications, we don't want a DOS
303type of application that nests large amounts of mutexes to create a large
304PI chain, and have the code holding spin locks while looking at a large
305amount of data. So to prevent this, the implementation not only implements
306a maximum lock depth, but also only holds at most two different locks at a
307time, as it walks the PI chain. More about this below.
308
309
310Mutex owner and flags
311---------------------
312
313The mutex structure contains a pointer to the owner of the mutex. If the
314mutex is not owned, this owner is set to NULL. Since all architectures
315have the task structure on at least a four byte alignment (and if this is
316not true, the rtmutex.c code will be broken!), this allows for the two
317least significant bits to be used as flags. This part is also described
318in Documentation/rt-mutex.txt, but will also be briefly described here.
319
320Bit 0 is used as the "Pending Owner" flag. This is described later.
321Bit 1 is used as the "Has Waiters" flags. This is also described later
322 in more detail, but is set whenever there are waiters on a mutex.
323
324
325cmpxchg Tricks
326--------------
327
328Some architectures implement an atomic cmpxchg (Compare and Exchange). This
329is used (when applicable) to keep the fast path of grabbing and releasing
330mutexes short.
331
332cmpxchg is basically the following function performed atomically:
333
334unsigned long _cmpxchg(unsigned long *A, unsigned long *B, unsigned long *C)
335{
336 unsigned long T = *A;
337 if (*A == *B) {
338 *A = *C;
339 }
340 return T;
341}
342#define cmpxchg(a,b,c) _cmpxchg(&a,&b,&c)
343
344This is really nice to have, since it allows you to only update a variable
345if the variable is what you expect it to be. You know if it succeeded if
346the return value (the old value of A) is equal to B.
347
348The macro rt_mutex_cmpxchg is used to try to lock and unlock mutexes. If
349the architecture does not support CMPXCHG, then this macro is simply set
350to fail every time. But if CMPXCHG is supported, then this will
351help out extremely to keep the fast path short.
352
353The use of rt_mutex_cmpxchg with the flags in the owner field help optimize
354the system for architectures that support it. This will also be explained
355later in this document.
356
357
358Priority adjustments
359--------------------
360
361The implementation of the PI code in rtmutex.c has several places that a
362process must adjust its priority. With the help of the pi_list of a
363process this is rather easy to know what needs to be adjusted.
364
365The functions implementing the task adjustments are rt_mutex_adjust_prio,
366__rt_mutex_adjust_prio (same as the former, but expects the task pi_lock
367to already be taken), rt_mutex_get_prio, and rt_mutex_setprio.
368
369rt_mutex_getprio and rt_mutex_setprio are only used in __rt_mutex_adjust_prio.
370
371rt_mutex_getprio returns the priority that the task should have. Either the
372task's own normal priority, or if a process of a higher priority is waiting on
373a mutex owned by the task, then that higher priority should be returned.
374Since the pi_list of a task holds an order by priority list of all the top
375waiters of all the mutexes that the task owns, rt_mutex_getprio simply needs
376to compare the top pi waiter to its own normal priority, and return the higher
377priority back.
378
379(Note: if looking at the code, you will notice that the lower number of
380 prio is returned. This is because the prio field in the task structure
381 is an inverse order of the actual priority. So a "prio" of 5 is
382 of higher priority than a "prio" of 10.)
383
384__rt_mutex_adjust_prio examines the result of rt_mutex_getprio, and if the
385result does not equal the task's current priority, then rt_mutex_setprio
386is called to adjust the priority of the task to the new priority.
387Note that rt_mutex_setprio is defined in kernel/sched.c to implement the
388actual change in priority.
389
390It is interesting to note that __rt_mutex_adjust_prio can either increase
391or decrease the priority of the task. In the case that a higher priority
392process has just blocked on a mutex owned by the task, __rt_mutex_adjust_prio
393would increase/boost the task's priority. But if a higher priority task
394were for some reason to leave the mutex (timeout or signal), this same function
395would decrease/unboost the priority of the task. That is because the pi_list
396always contains the highest priority task that is waiting on a mutex owned
397by the task, so we only need to compare the priority of that top pi waiter
398to the normal priority of the given task.
399
400
401High level overview of the PI chain walk
402----------------------------------------
403
404The PI chain walk is implemented by the function rt_mutex_adjust_prio_chain.
405
406The implementation has gone through several iterations, and has ended up
407with what we believe is the best. It walks the PI chain by only grabbing
408at most two locks at a time, and is very efficient.
409
410The rt_mutex_adjust_prio_chain can be used either to boost or lower process
411priorities.
412
413rt_mutex_adjust_prio_chain is called with a task to be checked for PI
414(de)boosting (the owner of a mutex that a process is blocking on), a flag to
415check for deadlocking, the mutex that the task owns, and a pointer to a waiter
416that is the process's waiter struct that is blocked on the mutex (although this
417parameter may be NULL for deboosting).
418
419For this explanation, I will not mention deadlock detection. This explanation
420will try to stay at a high level.
421
422When this function is called, there are no locks held. That also means
423that the state of the owner and lock can change when entered into this function.
424
425Before this function is called, the task has already had rt_mutex_adjust_prio
426performed on it. This means that the task is set to the priority that it
427should be at, but the plist nodes of the task's waiter have not been updated
428with the new priorities, and that this task may not be in the proper locations
429in the pi_lists and wait_lists that the task is blocked on. This function
430solves all that.
431
432A loop is entered, where task is the owner to be checked for PI changes that
433was passed by parameter (for the first iteration). The pi_lock of this task is
434taken to prevent any more changes to the pi_list of the task. This also
435prevents new tasks from completing the blocking on a mutex that is owned by this
436task.
437
438If the task is not blocked on a mutex then the loop is exited. We are at
439the top of the PI chain.
440
441A check is now done to see if the original waiter (the process that is blocked
442on the current mutex) is the top pi waiter of the task. That is, is this
443waiter on the top of the task's pi_list. If it is not, it either means that
444there is another process higher in priority that is blocked on one of the
445mutexes that the task owns, or that the waiter has just woken up via a signal
446or timeout and has left the PI chain. In either case, the loop is exited, since
447we don't need to do any more changes to the priority of the current task, or any
448task that owns a mutex that this current task is waiting on. A priority chain
449walk is only needed when a new top pi waiter is made to a task.
450
451The next check sees if the task's waiter plist node has the priority equal to
452the priority the task is set at. If they are equal, then we are done with
453the loop. Remember that the function started with the priority of the
454task adjusted, but the plist nodes that hold the task in other processes
455pi_lists have not been adjusted.
456
457Next, we look at the mutex that the task is blocked on. The mutex's wait_lock
458is taken. This is done by a spin_trylock, because the locking order of the
459pi_lock and wait_lock goes in the opposite direction. If we fail to grab the
460lock, the pi_lock is released, and we restart the loop.
461
462Now that we have both the pi_lock of the task as well as the wait_lock of
463the mutex the task is blocked on, we update the task's waiter's plist node
464that is located on the mutex's wait_list.
465
466Now we release the pi_lock of the task.
467
468Next the owner of the mutex has its pi_lock taken, so we can update the
469task's entry in the owner's pi_list. If the task is the highest priority
470process on the mutex's wait_list, then we remove the previous top waiter
471from the owner's pi_list, and replace it with the task.
472
473Note: It is possible that the task was the current top waiter on the mutex,
474 in which case the task is not yet on the pi_list of the waiter. This
475 is OK, since plist_del does nothing if the plist node is not on any
476 list.
477
478If the task was not the top waiter of the mutex, but it was before we
479did the priority updates, that means we are deboosting/lowering the
480task. In this case, the task is removed from the pi_list of the owner,
481and the new top waiter is added.
482
483Lastly, we unlock both the pi_lock of the task, as well as the mutex's
484wait_lock, and continue the loop again. On the next iteration of the
485loop, the previous owner of the mutex will be the task that will be
486processed.
487
488Note: One might think that the owner of this mutex might have changed
489 since we just grab the mutex's wait_lock. And one could be right.
490 The important thing to remember is that the owner could not have
491 become the task that is being processed in the PI chain, since
492 we have taken that task's pi_lock at the beginning of the loop.
493 So as long as there is an owner of this mutex that is not the same
494 process as the tasked being worked on, we are OK.
495
496 Looking closely at the code, one might be confused. The check for the
497 end of the PI chain is when the task isn't blocked on anything or the
498 task's waiter structure "task" element is NULL. This check is
499 protected only by the task's pi_lock. But the code to unlock the mutex
500 sets the task's waiter structure "task" element to NULL with only
501 the protection of the mutex's wait_lock, which was not taken yet.
502 Isn't this a race condition if the task becomes the new owner?
503
504 The answer is No! The trick is the spin_trylock of the mutex's
505 wait_lock. If we fail that lock, we release the pi_lock of the
506 task and continue the loop, doing the end of PI chain check again.
507
508 In the code to release the lock, the wait_lock of the mutex is held
509 the entire time, and it is not let go when we grab the pi_lock of the
510 new owner of the mutex. So if the switch of a new owner were to happen
511 after the check for end of the PI chain and the grabbing of the
512 wait_lock, the unlocking code would spin on the new owner's pi_lock
513 but never give up the wait_lock. So the PI chain loop is guaranteed to
514 fail the spin_trylock on the wait_lock, release the pi_lock, and
515 try again.
516
517 If you don't quite understand the above, that's OK. You don't have to,
518 unless you really want to make a proof out of it ;)
519
520
521Pending Owners and Lock stealing
522--------------------------------
523
524One of the flags in the owner field of the mutex structure is "Pending Owner".
525What this means is that an owner was chosen by the process releasing the
526mutex, but that owner has yet to wake up and actually take the mutex.
527
528Why is this important? Why can't we just give the mutex to another process
529and be done with it?
530
531The PI code is to help with real-time processes, and to let the highest
532priority process run as long as possible with little latencies and delays.
533If a high priority process owns a mutex that a lower priority process is
534blocked on, when the mutex is released it would be given to the lower priority
535process. What if the higher priority process wants to take that mutex again.
536The high priority process would fail to take that mutex that it just gave up
537and it would need to boost the lower priority process to run with full
538latency of that critical section (since the low priority process just entered
539it).
540
541There's no reason a high priority process that gives up a mutex should be
542penalized if it tries to take that mutex again. If the new owner of the
543mutex has not woken up yet, there's no reason that the higher priority process
544could not take that mutex away.
545
546To solve this, we introduced Pending Ownership and Lock Stealing. When a
547new process is given a mutex that it was blocked on, it is only given
548pending ownership. This means that it's the new owner, unless a higher
549priority process comes in and tries to grab that mutex. If a higher priority
550process does come along and wants that mutex, we let the higher priority
551process "steal" the mutex from the pending owner (only if it is still pending)
552and continue with the mutex.
553
554
555Taking of a mutex (The walk through)
556------------------------------------
557
558OK, now let's take a look at the detailed walk through of what happens when
559taking a mutex.
560
561The first thing that is tried is the fast taking of the mutex. This is
562done when we have CMPXCHG enabled (otherwise the fast taking automatically
563fails). Only when the owner field of the mutex is NULL can the lock be
564taken with the CMPXCHG and nothing else needs to be done.
565
566If there is contention on the lock, whether it is owned or pending owner
567we go about the slow path (rt_mutex_slowlock).
568
569The slow path function is where the task's waiter structure is created on
570the stack. This is because the waiter structure is only needed for the
571scope of this function. The waiter structure holds the nodes to store
572the task on the wait_list of the mutex, and if need be, the pi_list of
573the owner.
574
575The wait_lock of the mutex is taken since the slow path of unlocking the
576mutex also takes this lock.
577
578We then call try_to_take_rt_mutex. This is where the architecture that
579does not implement CMPXCHG would always grab the lock (if there's no
580contention).
581
582try_to_take_rt_mutex is used every time the task tries to grab a mutex in the
583slow path. The first thing that is done here is an atomic setting of
584the "Has Waiters" flag of the mutex's owner field. Yes, this could really
585be false, because if the the mutex has no owner, there are no waiters and
586the current task also won't have any waiters. But we don't have the lock
587yet, so we assume we are going to be a waiter. The reason for this is to
588play nice for those architectures that do have CMPXCHG. By setting this flag
589now, the owner of the mutex can't release the mutex without going into the
590slow unlock path, and it would then need to grab the wait_lock, which this
591code currently holds. So setting the "Has Waiters" flag forces the owner
592to synchronize with this code.
593
594Now that we know that we can't have any races with the owner releasing the
595mutex, we check to see if we can take the ownership. This is done if the
596mutex doesn't have a owner, or if we can steal the mutex from a pending
597owner. Let's look at the situations we have here.
598
599 1) Has owner that is pending
600 ----------------------------
601
602 The mutex has a owner, but it hasn't woken up and the mutex flag
603 "Pending Owner" is set. The first check is to see if the owner isn't the
604 current task. This is because this function is also used for the pending
605 owner to grab the mutex. When a pending owner wakes up, it checks to see
606 if it can take the mutex, and this is done if the owner is already set to
607 itself. If so, we succeed and leave the function, clearing the "Pending
608 Owner" bit.
609
610 If the pending owner is not current, we check to see if the current priority is
611 higher than the pending owner. If not, we fail the function and return.
612
613 There's also something special about a pending owner. That is a pending owner
614 is never blocked on a mutex. So there is no PI chain to worry about. It also
615 means that if the mutex doesn't have any waiters, there's no accounting needed
616 to update the pending owner's pi_list, since we only worry about processes
617 blocked on the current mutex.
618
619 If there are waiters on this mutex, and we just stole the ownership, we need
620 to take the top waiter, remove it from the pi_list of the pending owner, and
621 add it to the current pi_list. Note that at this moment, the pending owner
622 is no longer on the list of waiters. This is fine, since the pending owner
623 would add itself back when it realizes that it had the ownership stolen
624 from itself. When the pending owner tries to grab the mutex, it will fail
625 in try_to_take_rt_mutex if the owner field points to another process.
626
627 2) No owner
628 -----------
629
630 If there is no owner (or we successfully stole the lock), we set the owner
631 of the mutex to current, and set the flag of "Has Waiters" if the current
632 mutex actually has waiters, or we clear the flag if it doesn't. See, it was
633 OK that we set that flag early, since now it is cleared.
634
635 3) Failed to grab ownership
636 ---------------------------
637
638 The most interesting case is when we fail to take ownership. This means that
639 there exists an owner, or there's a pending owner with equal or higher
640 priority than the current task.
641
642We'll continue on the failed case.
643
644If the mutex has a timeout, we set up a timer to go off to break us out
645of this mutex if we failed to get it after a specified amount of time.
646
647Now we enter a loop that will continue to try to take ownership of the mutex, or
648fail from a timeout or signal.
649
650Once again we try to take the mutex. This will usually fail the first time
651in the loop, since it had just failed to get the mutex. But the second time
652in the loop, this would likely succeed, since the task would likely be
653the pending owner.
654
655If the mutex is TASK_INTERRUPTIBLE a check for signals and timeout is done
656here.
657
658The waiter structure has a "task" field that points to the task that is blocked
659on the mutex. This field can be NULL the first time it goes through the loop
660or if the task is a pending owner and had it's mutex stolen. If the "task"
661field is NULL then we need to set up the accounting for it.
662
663Task blocks on mutex
664--------------------
665
666The accounting of a mutex and process is done with the waiter structure of
667the process. The "task" field is set to the process, and the "lock" field
668to the mutex. The plist nodes are initialized to the processes current
669priority.
670
671Since the wait_lock was taken at the entry of the slow lock, we can safely
672add the waiter to the wait_list. If the current process is the highest
673priority process currently waiting on this mutex, then we remove the
674previous top waiter process (if it exists) from the pi_list of the owner,
675and add the current process to that list. Since the pi_list of the owner
676has changed, we call rt_mutex_adjust_prio on the owner to see if the owner
677should adjust its priority accordingly.
678
679If the owner is also blocked on a lock, and had its pi_list changed
680(or deadlock checking is on), we unlock the wait_lock of the mutex and go ahead
681and run rt_mutex_adjust_prio_chain on the owner, as described earlier.
682
683Now all locks are released, and if the current process is still blocked on a
684mutex (waiter "task" field is not NULL), then we go to sleep (call schedule).
685
686Waking up in the loop
687---------------------
688
689The schedule can then wake up for a few reasons.
690 1) we were given pending ownership of the mutex.
691 2) we received a signal and was TASK_INTERRUPTIBLE
692 3) we had a timeout and was TASK_INTERRUPTIBLE
693
694In any of these cases, we continue the loop and once again try to grab the
695ownership of the mutex. If we succeed, we exit the loop, otherwise we continue
696and on signal and timeout, will exit the loop, or if we had the mutex stolen
697we just simply add ourselves back on the lists and go back to sleep.
698
699Note: For various reasons, because of timeout and signals, the steal mutex
700 algorithm needs to be careful. This is because the current process is
701 still on the wait_list. And because of dynamic changing of priorities,
702 especially on SCHED_OTHER tasks, the current process can be the
703 highest priority task on the wait_list.
704
705Failed to get mutex on Timeout or Signal
706----------------------------------------
707
708If a timeout or signal occurred, the waiter's "task" field would not be
709NULL and the task needs to be taken off the wait_list of the mutex and perhaps
710pi_list of the owner. If this process was a high priority process, then
711the rt_mutex_adjust_prio_chain needs to be executed again on the owner,
712but this time it will be lowering the priorities.
713
714
715Unlocking the Mutex
716-------------------
717
718The unlocking of a mutex also has a fast path for those architectures with
719CMPXCHG. Since the taking of a mutex on contention always sets the
720"Has Waiters" flag of the mutex's owner, we use this to know if we need to
721take the slow path when unlocking the mutex. If the mutex doesn't have any
722waiters, the owner field of the mutex would equal the current process and
723the mutex can be unlocked by just replacing the owner field with NULL.
724
725If the owner field has the "Has Waiters" bit set (or CMPXCHG is not available),
726the slow unlock path is taken.
727
728The first thing done in the slow unlock path is to take the wait_lock of the
729mutex. This synchronizes the locking and unlocking of the mutex.
730
731A check is made to see if the mutex has waiters or not. On architectures that
732do not have CMPXCHG, this is the location that the owner of the mutex will
733determine if a waiter needs to be awoken or not. On architectures that
734do have CMPXCHG, that check is done in the fast path, but it is still needed
735in the slow path too. If a waiter of a mutex woke up because of a signal
736or timeout between the time the owner failed the fast path CMPXCHG check and
737the grabbing of the wait_lock, the mutex may not have any waiters, thus the
738owner still needs to make this check. If there are no waiters than the mutex
739owner field is set to NULL, the wait_lock is released and nothing more is
740needed.
741
742If there are waiters, then we need to wake one up and give that waiter
743pending ownership.
744
745On the wake up code, the pi_lock of the current owner is taken. The top
746waiter of the lock is found and removed from the wait_list of the mutex
747as well as the pi_list of the current owner. The task field of the new
748pending owner's waiter structure is set to NULL, and the owner field of the
749mutex is set to the new owner with the "Pending Owner" bit set, as well
750as the "Has Waiters" bit if there still are other processes blocked on the
751mutex.
752
753The pi_lock of the previous owner is released, and the new pending owner's
754pi_lock is taken. Remember that this is the trick to prevent the race
755condition in rt_mutex_adjust_prio_chain from adding itself as a waiter
756on the mutex.
757
758We now clear the "pi_blocked_on" field of the new pending owner, and if
759the mutex still has waiters pending, we add the new top waiter to the pi_list
760of the pending owner.
761
762Finally we unlock the pi_lock of the pending owner and wake it up.
763
764
765Contact
766-------
767
768For updates on this document, please email Steven Rostedt <rostedt@goodmis.org>
769
770
771Credits
772-------
773
774Author: Steven Rostedt <rostedt@goodmis.org>
775
776Reviewers: Ingo Molnar, Thomas Gleixner, Thomas Duetsch, and Randy Dunlap
777
778Updates
779-------
780
781This document was originally written for 2.6.17-rc3-mm1
diff --git a/Documentation/rt-mutex.txt b/Documentation/rt-mutex.txt
new file mode 100644
index 000000000000..243393d882ee
--- /dev/null
+++ b/Documentation/rt-mutex.txt
@@ -0,0 +1,79 @@
1RT-mutex subsystem with PI support
2----------------------------------
3
4RT-mutexes with priority inheritance are used to support PI-futexes,
5which enable pthread_mutex_t priority inheritance attributes
6(PTHREAD_PRIO_INHERIT). [See Documentation/pi-futex.txt for more details
7about PI-futexes.]
8
9This technology was developed in the -rt tree and streamlined for
10pthread_mutex support.
11
12Basic principles:
13-----------------
14
15RT-mutexes extend the semantics of simple mutexes by the priority
16inheritance protocol.
17
18A low priority owner of a rt-mutex inherits the priority of a higher
19priority waiter until the rt-mutex is released. If the temporarily
20boosted owner blocks on a rt-mutex itself it propagates the priority
21boosting to the owner of the other rt_mutex it gets blocked on. The
22priority boosting is immediately removed once the rt_mutex has been
23unlocked.
24
25This approach allows us to shorten the block of high-prio tasks on
26mutexes which protect shared resources. Priority inheritance is not a
27magic bullet for poorly designed applications, but it allows
28well-designed applications to use userspace locks in critical parts of
29an high priority thread, without losing determinism.
30
31The enqueueing of the waiters into the rtmutex waiter list is done in
32priority order. For same priorities FIFO order is chosen. For each
33rtmutex, only the top priority waiter is enqueued into the owner's
34priority waiters list. This list too queues in priority order. Whenever
35the top priority waiter of a task changes (for example it timed out or
36got a signal), the priority of the owner task is readjusted. [The
37priority enqueueing is handled by "plists", see include/linux/plist.h
38for more details.]
39
40RT-mutexes are optimized for fastpath operations and have no internal
41locking overhead when locking an uncontended mutex or unlocking a mutex
42without waiters. The optimized fastpath operations require cmpxchg
43support. [If that is not available then the rt-mutex internal spinlock
44is used]
45
46The state of the rt-mutex is tracked via the owner field of the rt-mutex
47structure:
48
49rt_mutex->owner holds the task_struct pointer of the owner. Bit 0 and 1
50are used to keep track of the "owner is pending" and "rtmutex has
51waiters" state.
52
53 owner bit1 bit0
54 NULL 0 0 mutex is free (fast acquire possible)
55 NULL 0 1 invalid state
56 NULL 1 0 Transitional state*
57 NULL 1 1 invalid state
58 taskpointer 0 0 mutex is held (fast release possible)
59 taskpointer 0 1 task is pending owner
60 taskpointer 1 0 mutex is held and has waiters
61 taskpointer 1 1 task is pending owner and mutex has waiters
62
63Pending-ownership handling is a performance optimization:
64pending-ownership is assigned to the first (highest priority) waiter of
65the mutex, when the mutex is released. The thread is woken up and once
66it starts executing it can acquire the mutex. Until the mutex is taken
67by it (bit 0 is cleared) a competing higher priority thread can "steal"
68the mutex which puts the woken up thread back on the waiters list.
69
70The pending-ownership optimization is especially important for the
71uninterrupted workflow of high-prio tasks which repeatedly
72takes/releases locks that have lower-prio waiters. Without this
73optimization the higher-prio thread would ping-pong to the lower-prio
74task [because at unlock time we always assign a new owner].
75
76(*) The "mutex has waiters" bit gets set to take the lock. If the lock
77doesn't already have an owner, this bit is quickly cleared if there are
78no waiters. So this is a transitional state to synchronize with looking
79at the owner field of the mutex and the mutex owner releasing the lock.
diff --git a/Documentation/scsi/ppa.txt b/Documentation/scsi/ppa.txt
index 0dac88d86d87..5d9223bc1bd5 100644
--- a/Documentation/scsi/ppa.txt
+++ b/Documentation/scsi/ppa.txt
@@ -12,5 +12,3 @@ http://www.torque.net/parport/
12Email list for Linux Parport 12Email list for Linux Parport
13linux-parport@torque.net 13linux-parport@torque.net
14 14
15Email for problems with ZIP or ZIP Plus drivers
16campbell@torque.net
diff --git a/Documentation/sound/alsa/ALSA-Configuration.txt b/Documentation/sound/alsa/ALSA-Configuration.txt
index 87d76a5c73d0..f61af23dd85d 100644
--- a/Documentation/sound/alsa/ALSA-Configuration.txt
+++ b/Documentation/sound/alsa/ALSA-Configuration.txt
@@ -472,6 +472,22 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
472 472
473 The power-management is supported. 473 The power-management is supported.
474 474
475 Module snd-darla20
476 ------------------
477
478 Module for Echoaudio Darla20
479
480 This module supports multiple cards.
481 The driver requires the firmware loader support on kernel.
482
483 Module snd-darla24
484 ------------------
485
486 Module for Echoaudio Darla24
487
488 This module supports multiple cards.
489 The driver requires the firmware loader support on kernel.
490
475 Module snd-dt019x 491 Module snd-dt019x
476 ----------------- 492 -----------------
477 493
@@ -499,6 +515,14 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
499 515
500 The power-management is supported. 516 The power-management is supported.
501 517
518 Module snd-echo3g
519 -----------------
520
521 Module for Echoaudio 3G cards (Gina3G/Layla3G)
522
523 This module supports multiple cards.
524 The driver requires the firmware loader support on kernel.
525
502 Module snd-emu10k1 526 Module snd-emu10k1
503 ------------------ 527 ------------------
504 528
@@ -657,6 +681,22 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
657 681
658 The power-management is supported. 682 The power-management is supported.
659 683
684 Module snd-gina20
685 -----------------
686
687 Module for Echoaudio Gina20
688
689 This module supports multiple cards.
690 The driver requires the firmware loader support on kernel.
691
692 Module snd-gina24
693 -----------------
694
695 Module for Echoaudio Gina24
696
697 This module supports multiple cards.
698 The driver requires the firmware loader support on kernel.
699
660 Module snd-gusclassic 700 Module snd-gusclassic
661 --------------------- 701 ---------------------
662 702
@@ -760,12 +800,18 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
760 basic fixed pin assignment w/o SPDIF 800 basic fixed pin assignment w/o SPDIF
761 auto auto-config reading BIOS (default) 801 auto auto-config reading BIOS (default)
762 802
763 ALC882/883/885 803 ALC882/885
764 3stack-dig 3-jack with SPDIF I/O 804 3stack-dig 3-jack with SPDIF I/O
765 6stck-dig 6-jack digital with SPDIF I/O 805 6stck-dig 6-jack digital with SPDIF I/O
766 auto auto-config reading BIOS (default) 806 auto auto-config reading BIOS (default)
767 807
768 ALC861 808 ALC883/888
809 3stack-dig 3-jack with SPDIF I/O
810 6stack-dig 6-jack digital with SPDIF I/O
811 6stack-dig-demo 6-stack digital for Intel demo board
812 auto auto-config reading BIOS (default)
813
814 ALC861/660
769 3stack 3-jack 815 3stack 3-jack
770 3stack-dig 3-jack with SPDIF I/O 816 3stack-dig 3-jack with SPDIF I/O
771 6stack-dig 6-jack with SPDIF I/O 817 6stack-dig 6-jack with SPDIF I/O
@@ -937,6 +983,30 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
937 driver isn't configured properly or you want to try another 983 driver isn't configured properly or you want to try another
938 type for testing. 984 type for testing.
939 985
986 Module snd-indigo
987 -----------------
988
989 Module for Echoaudio Indigo
990
991 This module supports multiple cards.
992 The driver requires the firmware loader support on kernel.
993
994 Module snd-indigodj
995 -------------------
996
997 Module for Echoaudio Indigo DJ
998
999 This module supports multiple cards.
1000 The driver requires the firmware loader support on kernel.
1001
1002 Module snd-indigoio
1003 -------------------
1004
1005 Module for Echoaudio Indigo IO
1006
1007 This module supports multiple cards.
1008 The driver requires the firmware loader support on kernel.
1009
940 Module snd-intel8x0 1010 Module snd-intel8x0
941 ------------------- 1011 -------------------
942 1012
@@ -1036,6 +1106,22 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
1036 1106
1037 This module supports multiple cards. 1107 This module supports multiple cards.
1038 1108
1109 Module snd-layla20
1110 ------------------
1111
1112 Module for Echoaudio Layla20
1113
1114 This module supports multiple cards.
1115 The driver requires the firmware loader support on kernel.
1116
1117 Module snd-layla24
1118 ------------------
1119
1120 Module for Echoaudio Layla24
1121
1122 This module supports multiple cards.
1123 The driver requires the firmware loader support on kernel.
1124
1039 Module snd-maestro3 1125 Module snd-maestro3
1040 ------------------- 1126 -------------------
1041 1127
@@ -1056,6 +1142,14 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
1056 1142
1057 The power-management is supported. 1143 The power-management is supported.
1058 1144
1145 Module snd-mia
1146 ---------------
1147
1148 Module for Echoaudio Mia
1149
1150 This module supports multiple cards.
1151 The driver requires the firmware loader support on kernel.
1152
1059 Module snd-miro 1153 Module snd-miro
1060 --------------- 1154 ---------------
1061 1155
@@ -1088,6 +1182,14 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed.
1088 When no hotplug fw loader is available, you need to load the 1182 When no hotplug fw loader is available, you need to load the
1089 firmware via mixartloader utility in alsa-tools package. 1183 firmware via mixartloader utility in alsa-tools package.
1090 1184
1185 Module snd-mona
1186 ---------------
1187
1188 Module for Echoaudio Mona
1189
1190 This module supports multiple cards.
1191 The driver requires the firmware loader support on kernel.
1192
1091 Module snd-mpu401 1193 Module snd-mpu401
1092 ----------------- 1194 -----------------
1093 1195
diff --git a/Documentation/video4linux/README.pvrusb2 b/Documentation/video4linux/README.pvrusb2
new file mode 100644
index 000000000000..c73a32c34528
--- /dev/null
+++ b/Documentation/video4linux/README.pvrusb2
@@ -0,0 +1,212 @@
1
2$Id$
3Mike Isely <isely@pobox.com>
4
5 pvrusb2 driver
6
7Background:
8
9 This driver is intended for the "Hauppauge WinTV PVR USB 2.0", which
10 is a USB 2.0 hosted TV Tuner. This driver is a work in progress.
11 Its history started with the reverse-engineering effort by Björn
12 Danielsson <pvrusb2@dax.nu> whose web page can be found here:
13
14 http://pvrusb2.dax.nu/
15
16 From there Aurelien Alleaume <slts@free.fr> began an effort to
17 create a video4linux compatible driver. I began with Aurelien's
18 last known snapshot and evolved the driver to the state it is in
19 here.
20
21 More information on this driver can be found at:
22
23 http://www.isely.net/pvrusb2.html
24
25
26 This driver has a strong separation of layers. They are very
27 roughly:
28
29 1a. Low level wire-protocol implementation with the device.
30
31 1b. I2C adaptor implementation and corresponding I2C client drivers
32 implemented elsewhere in V4L.
33
34 1c. High level hardware driver implementation which coordinates all
35 activities that ensure correct operation of the device.
36
37 2. A "context" layer which manages instancing of driver, setup,
38 tear-down, arbitration, and interaction with high level
39 interfaces appropriately as devices are hotplugged in the
40 system.
41
42 3. High level interfaces which glue the driver to various published
43 Linux APIs (V4L, sysfs, maybe DVB in the future).
44
45 The most important shearing layer is between the top 2 layers. A
46 lot of work went into the driver to ensure that any kind of
47 conceivable API can be laid on top of the core driver. (Yes, the
48 driver internally leverages V4L to do its work but that really has
49 nothing to do with the API published by the driver to the outside
50 world.) The architecture allows for different APIs to
51 simultaneously access the driver. I have a strong sense of fairness
52 about APIs and also feel that it is a good design principle to keep
53 implementation and interface isolated from each other. Thus while
54 right now the V4L high level interface is the most complete, the
55 sysfs high level interface will work equally well for similar
56 functions, and there's no reason I see right now why it shouldn't be
57 possible to produce a DVB high level interface that can sit right
58 alongside V4L.
59
60 NOTE: Complete documentation on the pvrusb2 driver is contained in
61 the html files within the doc directory; these are exactly the same
62 as what is on the web site at the time. Browse those files
63 (especially the FAQ) before asking questions.
64
65
66Building
67
68 To build these modules essentially amounts to just running "Make",
69 but you need the kernel source tree nearby and you will likely also
70 want to set a few controlling environment variables first in order
71 to link things up with that source tree. Please see the Makefile
72 here for comments that explain how to do that.
73
74
75Source file list / functional overview:
76
77 (Note: The term "module" used below generally refers to loosely
78 defined functional units within the pvrusb2 driver and bears no
79 relation to the Linux kernel's concept of a loadable module.)
80
81 pvrusb2-audio.[ch] - This is glue logic that resides between this
82 driver and the msp3400.ko I2C client driver (which is found
83 elsewhere in V4L).
84
85 pvrusb2-context.[ch] - This module implements the context for an
86 instance of the driver. Everything else eventually ties back to
87 or is otherwise instanced within the data structures implemented
88 here. Hotplugging is ultimately coordinated here. All high level
89 interfaces tie into the driver through this module. This module
90 helps arbitrate each interface's access to the actual driver core,
91 and is designed to allow concurrent access through multiple
92 instances of multiple interfaces (thus you can for example change
93 the tuner's frequency through sysfs while simultaneously streaming
94 video through V4L out to an instance of mplayer).
95
96 pvrusb2-debug.h - This header defines a printk() wrapper and a mask
97 of debugging bit definitions for the various kinds of debug
98 messages that can be enabled within the driver.
99
100 pvrusb2-debugifc.[ch] - This module implements a crude command line
101 oriented debug interface into the driver. Aside from being part
102 of the process for implementing manual firmware extraction (see
103 the pvrusb2 web site mentioned earlier), probably I'm the only one
104 who has ever used this. It is mainly a debugging aid.
105
106 pvrusb2-eeprom.[ch] - This is glue logic that resides between this
107 driver the tveeprom.ko module, which is itself implemented
108 elsewhere in V4L.
109
110 pvrusb2-encoder.[ch] - This module implements all protocol needed to
111 interact with the Conexant mpeg2 encoder chip within the pvrusb2
112 device. It is a crude echo of corresponding logic in ivtv,
113 however the design goals (strict isolation) and physical layer
114 (proxy through USB instead of PCI) are enough different that this
115 implementation had to be completely different.
116
117 pvrusb2-hdw-internal.h - This header defines the core data structure
118 in the driver used to track ALL internal state related to control
119 of the hardware. Nobody outside of the core hardware-handling
120 modules should have any business using this header. All external
121 access to the driver should be through one of the high level
122 interfaces (e.g. V4L, sysfs, etc), and in fact even those high
123 level interfaces are restricted to the API defined in
124 pvrusb2-hdw.h and NOT this header.
125
126 pvrusb2-hdw.h - This header defines the full internal API for
127 controlling the hardware. High level interfaces (e.g. V4L, sysfs)
128 will work through here.
129
130 pvrusb2-hdw.c - This module implements all the various bits of logic
131 that handle overall control of a specific pvrusb2 device.
132 (Policy, instantiation, and arbitration of pvrusb2 devices fall
133 within the jurisdiction of pvrusb-context not here).
134
135 pvrusb2-i2c-chips-*.c - These modules implement the glue logic to
136 tie together and configure various I2C modules as they attach to
137 the I2C bus. There are two versions of this file. The "v4l2"
138 version is intended to be used in-tree alongside V4L, where we
139 implement just the logic that makes sense for a pure V4L
140 environment. The "all" version is intended for use outside of
141 V4L, where we might encounter other possibly "challenging" modules
142 from ivtv or older kernel snapshots (or even the support modules
143 in the standalone snapshot).
144
145 pvrusb2-i2c-cmd-v4l1.[ch] - This module implements generic V4L1
146 compatible commands to the I2C modules. It is here where state
147 changes inside the pvrusb2 driver are translated into V4L1
148 commands that are in turn send to the various I2C modules.
149
150 pvrusb2-i2c-cmd-v4l2.[ch] - This module implements generic V4L2
151 compatible commands to the I2C modules. It is here where state
152 changes inside the pvrusb2 driver are translated into V4L2
153 commands that are in turn send to the various I2C modules.
154
155 pvrusb2-i2c-core.[ch] - This module provides an implementation of a
156 kernel-friendly I2C adaptor driver, through which other external
157 I2C client drivers (e.g. msp3400, tuner, lirc) may connect and
158 operate corresponding chips within the the pvrusb2 device. It is
159 through here that other V4L modules can reach into this driver to
160 operate specific pieces (and those modules are in turn driven by
161 glue logic which is coordinated by pvrusb2-hdw, doled out by
162 pvrusb2-context, and then ultimately made available to users
163 through one of the high level interfaces).
164
165 pvrusb2-io.[ch] - This module implements a very low level ring of
166 transfer buffers, required in order to stream data from the
167 device. This module is *very* low level. It only operates the
168 buffers and makes no attempt to define any policy or mechanism for
169 how such buffers might be used.
170
171 pvrusb2-ioread.[ch] - This module layers on top of pvrusb2-io.[ch]
172 to provide a streaming API usable by a read() system call style of
173 I/O. Right now this is the only layer on top of pvrusb2-io.[ch],
174 however the underlying architecture here was intended to allow for
175 other styles of I/O to be implemented with additonal modules, like
176 mmap()'ed buffers or something even more exotic.
177
178 pvrusb2-main.c - This is the top level of the driver. Module level
179 and USB core entry points are here. This is our "main".
180
181 pvrusb2-sysfs.[ch] - This is the high level interface which ties the
182 pvrusb2 driver into sysfs. Through this interface you can do
183 everything with the driver except actually stream data.
184
185 pvrusb2-tuner.[ch] - This is glue logic that resides between this
186 driver and the tuner.ko I2C client driver (which is found
187 elsewhere in V4L).
188
189 pvrusb2-util.h - This header defines some common macros used
190 throughout the driver. These macros are not really specific to
191 the driver, but they had to go somewhere.
192
193 pvrusb2-v4l2.[ch] - This is the high level interface which ties the
194 pvrusb2 driver into video4linux. It is through here that V4L
195 applications can open and operate the driver in the usual V4L
196 ways. Note that **ALL** V4L functionality is published only
197 through here and nowhere else.
198
199 pvrusb2-video-*.[ch] - This is glue logic that resides between this
200 driver and the saa711x.ko I2C client driver (which is found
201 elsewhere in V4L). Note that saa711x.ko used to be known as
202 saa7115.ko in ivtv. There are two versions of this; one is
203 selected depending on the particular saa711[5x].ko that is found.
204
205 pvrusb2.h - This header contains compile time tunable parameters
206 (and at the moment the driver has very little that needs to be
207 tuned).
208
209
210 -Mike Isely
211 isely@pobox.com
212
diff --git a/Documentation/watchdog/pcwd-watchdog.txt b/Documentation/watchdog/pcwd-watchdog.txt
index 12187a33e310..d9ee6336c1d4 100644
--- a/Documentation/watchdog/pcwd-watchdog.txt
+++ b/Documentation/watchdog/pcwd-watchdog.txt
@@ -22,78 +22,9 @@
22 to run the program with an "&" to run it in the background!) 22 to run the program with an "&" to run it in the background!)
23 23
24 If you want to write a program to be compatible with the PC Watchdog 24 If you want to write a program to be compatible with the PC Watchdog
25 driver, simply do the following: 25 driver, simply use of modify the watchdog test program:
26 26 Documentation/watchdog/src/watchdog-test.c
27-- Snippet of code -- 27
28/*
29 * Watchdog Driver Test Program
30 */
31
32#include <stdio.h>
33#include <stdlib.h>
34#include <string.h>
35#include <unistd.h>
36#include <fcntl.h>
37#include <sys/ioctl.h>
38#include <linux/types.h>
39#include <linux/watchdog.h>
40
41int fd;
42
43/*
44 * This function simply sends an IOCTL to the driver, which in turn ticks
45 * the PC Watchdog card to reset its internal timer so it doesn't trigger
46 * a computer reset.
47 */
48void keep_alive(void)
49{
50 int dummy;
51
52 ioctl(fd, WDIOC_KEEPALIVE, &dummy);
53}
54
55/*
56 * The main program. Run the program with "-d" to disable the card,
57 * or "-e" to enable the card.
58 */
59int main(int argc, char *argv[])
60{
61 fd = open("/dev/watchdog", O_WRONLY);
62
63 if (fd == -1) {
64 fprintf(stderr, "Watchdog device not enabled.\n");
65 fflush(stderr);
66 exit(-1);
67 }
68
69 if (argc > 1) {
70 if (!strncasecmp(argv[1], "-d", 2)) {
71 ioctl(fd, WDIOC_SETOPTIONS, WDIOS_DISABLECARD);
72 fprintf(stderr, "Watchdog card disabled.\n");
73 fflush(stderr);
74 exit(0);
75 } else if (!strncasecmp(argv[1], "-e", 2)) {
76 ioctl(fd, WDIOC_SETOPTIONS, WDIOS_ENABLECARD);
77 fprintf(stderr, "Watchdog card enabled.\n");
78 fflush(stderr);
79 exit(0);
80 } else {
81 fprintf(stderr, "-d to disable, -e to enable.\n");
82 fprintf(stderr, "run by itself to tick the card.\n");
83 fflush(stderr);
84 exit(0);
85 }
86 } else {
87 fprintf(stderr, "Watchdog Ticking Away!\n");
88 fflush(stderr);
89 }
90
91 while(1) {
92 keep_alive();
93 sleep(1);
94 }
95}
96-- End snippet --
97 28
98 Other IOCTL functions include: 29 Other IOCTL functions include:
99 30
diff --git a/Documentation/watchdog/src/watchdog-simple.c b/Documentation/watchdog/src/watchdog-simple.c
new file mode 100644
index 000000000000..85cf17c48669
--- /dev/null
+++ b/Documentation/watchdog/src/watchdog-simple.c
@@ -0,0 +1,15 @@
1#include <stdlib.h>
2#include <fcntl.h>
3
4int main(int argc, const char *argv[]) {
5 int fd = open("/dev/watchdog", O_WRONLY);
6 if (fd == -1) {
7 perror("watchdog");
8 exit(1);
9 }
10 while (1) {
11 write(fd, "\0", 1);
12 fsync(fd);
13 sleep(10);
14 }
15}
diff --git a/Documentation/watchdog/src/watchdog-test.c b/Documentation/watchdog/src/watchdog-test.c
new file mode 100644
index 000000000000..65f6c19cb865
--- /dev/null
+++ b/Documentation/watchdog/src/watchdog-test.c
@@ -0,0 +1,68 @@
1/*
2 * Watchdog Driver Test Program
3 */
4
5#include <stdio.h>
6#include <stdlib.h>
7#include <string.h>
8#include <unistd.h>
9#include <fcntl.h>
10#include <sys/ioctl.h>
11#include <linux/types.h>
12#include <linux/watchdog.h>
13
14int fd;
15
16/*
17 * This function simply sends an IOCTL to the driver, which in turn ticks
18 * the PC Watchdog card to reset its internal timer so it doesn't trigger
19 * a computer reset.
20 */
21void keep_alive(void)
22{
23 int dummy;
24
25 ioctl(fd, WDIOC_KEEPALIVE, &dummy);
26}
27
28/*
29 * The main program. Run the program with "-d" to disable the card,
30 * or "-e" to enable the card.
31 */
32int main(int argc, char *argv[])
33{
34 fd = open("/dev/watchdog", O_WRONLY);
35
36 if (fd == -1) {
37 fprintf(stderr, "Watchdog device not enabled.\n");
38 fflush(stderr);
39 exit(-1);
40 }
41
42 if (argc > 1) {
43 if (!strncasecmp(argv[1], "-d", 2)) {
44 ioctl(fd, WDIOC_SETOPTIONS, WDIOS_DISABLECARD);
45 fprintf(stderr, "Watchdog card disabled.\n");
46 fflush(stderr);
47 exit(0);
48 } else if (!strncasecmp(argv[1], "-e", 2)) {
49 ioctl(fd, WDIOC_SETOPTIONS, WDIOS_ENABLECARD);
50 fprintf(stderr, "Watchdog card enabled.\n");
51 fflush(stderr);
52 exit(0);
53 } else {
54 fprintf(stderr, "-d to disable, -e to enable.\n");
55 fprintf(stderr, "run by itself to tick the card.\n");
56 fflush(stderr);
57 exit(0);
58 }
59 } else {
60 fprintf(stderr, "Watchdog Ticking Away!\n");
61 fflush(stderr);
62 }
63
64 while(1) {
65 keep_alive();
66 sleep(1);
67 }
68}
diff --git a/Documentation/watchdog/watchdog-api.txt b/Documentation/watchdog/watchdog-api.txt
index 21ed51173662..958ff3d48be3 100644
--- a/Documentation/watchdog/watchdog-api.txt
+++ b/Documentation/watchdog/watchdog-api.txt
@@ -34,22 +34,7 @@ activates as soon as /dev/watchdog is opened and will reboot unless
34the watchdog is pinged within a certain time, this time is called the 34the watchdog is pinged within a certain time, this time is called the
35timeout or margin. The simplest way to ping the watchdog is to write 35timeout or margin. The simplest way to ping the watchdog is to write
36some data to the device. So a very simple watchdog daemon would look 36some data to the device. So a very simple watchdog daemon would look
37like this: 37like this source file: see Documentation/watchdog/src/watchdog-simple.c
38
39#include <stdlib.h>
40#include <fcntl.h>
41
42int main(int argc, const char *argv[]) {
43 int fd=open("/dev/watchdog",O_WRONLY);
44 if (fd==-1) {
45 perror("watchdog");
46 exit(1);
47 }
48 while(1) {
49 write(fd, "\0", 1);
50 sleep(10);
51 }
52}
53 38
54A more advanced driver could for example check that a HTTP server is 39A more advanced driver could for example check that a HTTP server is
55still responding before doing the write call to ping the watchdog. 40still responding before doing the write call to ping the watchdog.
@@ -110,7 +95,40 @@ current timeout using the GETTIMEOUT ioctl.
110 ioctl(fd, WDIOC_GETTIMEOUT, &timeout); 95 ioctl(fd, WDIOC_GETTIMEOUT, &timeout);
111 printf("The timeout was is %d seconds\n", timeout); 96 printf("The timeout was is %d seconds\n", timeout);
112 97
113Envinronmental monitoring: 98Pretimeouts:
99
100Some watchdog timers can be set to have a trigger go off before the
101actual time they will reset the system. This can be done with an NMI,
102interrupt, or other mechanism. This allows Linux to record useful
103information (like panic information and kernel coredumps) before it
104resets.
105
106 pretimeout = 10;
107 ioctl(fd, WDIOC_SETPRETIMEOUT, &pretimeout);
108
109Note that the pretimeout is the number of seconds before the time
110when the timeout will go off. It is not the number of seconds until
111the pretimeout. So, for instance, if you set the timeout to 60 seconds
112and the pretimeout to 10 seconds, the pretimout will go of in 50
113seconds. Setting a pretimeout to zero disables it.
114
115There is also a get function for getting the pretimeout:
116
117 ioctl(fd, WDIOC_GETPRETIMEOUT, &timeout);
118 printf("The pretimeout was is %d seconds\n", timeout);
119
120Not all watchdog drivers will support a pretimeout.
121
122Get the number of seconds before reboot:
123
124Some watchdog drivers have the ability to report the remaining time
125before the system will reboot. The WDIOC_GETTIMELEFT is the ioctl
126that returns the number of seconds before reboot.
127
128 ioctl(fd, WDIOC_GETTIMELEFT, &timeleft);
129 printf("The timeout was is %d seconds\n", timeleft);
130
131Environmental monitoring:
114 132
115All watchdog drivers are required return more information about the system, 133All watchdog drivers are required return more information about the system,
116some do temperature, fan and power level monitoring, some can tell you 134some do temperature, fan and power level monitoring, some can tell you
@@ -169,6 +187,10 @@ The watchdog saw a keepalive ping since it was last queried.
169 187
170 WDIOF_SETTIMEOUT Can set/get the timeout 188 WDIOF_SETTIMEOUT Can set/get the timeout
171 189
190The watchdog can do pretimeouts.
191
192 WDIOF_PRETIMEOUT Pretimeout (in seconds), get/set
193
172 194
173For those drivers that return any bits set in the option field, the 195For those drivers that return any bits set in the option field, the
174GETSTATUS and GETBOOTSTATUS ioctls can be used to ask for the current 196GETSTATUS and GETBOOTSTATUS ioctls can be used to ask for the current
diff --git a/Documentation/watchdog/watchdog.txt b/Documentation/watchdog/watchdog.txt
index dffda29c8799..4b1ff69cc19a 100644
--- a/Documentation/watchdog/watchdog.txt
+++ b/Documentation/watchdog/watchdog.txt
@@ -65,28 +65,7 @@ The external event interfaces on the WDT boards are not currently supported.
65Minor numbers are however allocated for it. 65Minor numbers are however allocated for it.
66 66
67 67
68Example Watchdog Driver 68Example Watchdog Driver: see Documentation/watchdog/src/watchdog-simple.c
69-----------------------
70
71#include <stdio.h>
72#include <unistd.h>
73#include <fcntl.h>
74
75int main(int argc, const char *argv[])
76{
77 int fd=open("/dev/watchdog",O_WRONLY);
78 if(fd==-1)
79 {
80 perror("watchdog");
81 exit(1);
82 }
83 while(1)
84 {
85 write(fd,"\0",1);
86 fsync(fd);
87 sleep(10);
88 }
89}
90 69
91 70
92Contact Information 71Contact Information