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authorTejun Heo <tj@kernel.org>2010-07-20 16:09:02 -0400
committerTejun Heo <tj@kernel.org>2010-07-23 07:14:49 -0400
commit181a51f6e040d0ac006d6adaf4a031ffa440f41c (patch)
treeed06062b8c606149497dffbb6a6ef0548cc44911
parent6ecd7c2dd9f5dd4f6e8f65c8027159f9c73b0e4c (diff)
slow-work: kill it
slow-work doesn't have any user left. Kill it. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: David Howells <dhowells@redhat.com>
Diffstat
-rw-r--r--Documentation/slow-work.txt322
-rw-r--r--include/linux/slow-work.h163
-rw-r--r--init/Kconfig24
-rw-r--r--kernel/Makefile2
-rw-r--r--kernel/slow-work-debugfs.c227
-rw-r--r--kernel/slow-work.c1068
-rw-r--r--kernel/slow-work.h72
-rw-r--r--kernel/sysctl.c8
8 files changed, 0 insertions, 1886 deletions
diff --git a/Documentation/slow-work.txt b/Documentation/slow-work.txt
deleted file mode 100644
index 9dbf4470c7e1..000000000000
--- a/Documentation/slow-work.txt
+++ /dev/null
@@ -1,322 +0,0 @@
1 ====================================
2 SLOW WORK ITEM EXECUTION THREAD POOL
3 ====================================
4
5By: David Howells <dhowells@redhat.com>
6
7The slow work item execution thread pool is a pool of threads for performing
8things that take a relatively long time, such as making mkdir calls.
9Typically, when processing something, these items will spend a lot of time
10blocking a thread on I/O, thus making that thread unavailable for doing other
11work.
12
13The standard workqueue model is unsuitable for this class of work item as that
14limits the owner to a single thread or a single thread per CPU. For some
15tasks, however, more threads - or fewer - are required.
16
17There is just one pool per system. It contains no threads unless something
18wants to use it - and that something must register its interest first. When
19the pool is active, the number of threads it contains is dynamic, varying
20between a maximum and minimum setting, depending on the load.
21
22
23====================
24CLASSES OF WORK ITEM
25====================
26
27This pool support two classes of work items:
28
29 (*) Slow work items.
30
31 (*) Very slow work items.
32
33The former are expected to finish much quicker than the latter.
34
35An operation of the very slow class may do a batch combination of several
36lookups, mkdirs, and a create for instance.
37
38An operation of the ordinarily slow class may, for example, write stuff or
39expand files, provided the time taken to do so isn't too long.
40
41Operations of both types may sleep during execution, thus tying up the thread
42loaned to it.
43
44A further class of work item is available, based on the slow work item class:
45
46 (*) Delayed slow work items.
47
48These are slow work items that have a timer to defer queueing of the item for
49a while.
50
51
52THREAD-TO-CLASS ALLOCATION
53--------------------------
54
55Not all the threads in the pool are available to work on very slow work items.
56The number will be between one and one fewer than the number of active threads.
57This is configurable (see the "Pool Configuration" section).
58
59All the threads are available to work on ordinarily slow work items, but a
60percentage of the threads will prefer to work on very slow work items.
61
62The configuration ensures that at least one thread will be available to work on
63very slow work items, and at least one thread will be available that won't work
64on very slow work items at all.
65
66
67=====================
68USING SLOW WORK ITEMS
69=====================
70
71Firstly, a module or subsystem wanting to make use of slow work items must
72register its interest:
73
74 int ret = slow_work_register_user(struct module *module);
75
76This will return 0 if successful, or a -ve error upon failure. The module
77pointer should be the module interested in using this facility (almost
78certainly THIS_MODULE).
79
80
81Slow work items may then be set up by:
82
83 (1) Declaring a slow_work struct type variable:
84
85 #include <linux/slow-work.h>
86
87 struct slow_work myitem;
88
89 (2) Declaring the operations to be used for this item:
90
91 struct slow_work_ops myitem_ops = {
92 .get_ref = myitem_get_ref,
93 .put_ref = myitem_put_ref,
94 .execute = myitem_execute,
95 };
96
97 [*] For a description of the ops, see section "Item Operations".
98
99 (3) Initialising the item:
100
101 slow_work_init(&myitem, &myitem_ops);
102
103 or:
104
105 delayed_slow_work_init(&myitem, &myitem_ops);
106
107 or:
108
109 vslow_work_init(&myitem, &myitem_ops);
110
111 depending on its class.
112
113A suitably set up work item can then be enqueued for processing:
114
115 int ret = slow_work_enqueue(&myitem);
116
117This will return a -ve error if the thread pool is unable to gain a reference
118on the item, 0 otherwise, or (for delayed work):
119
120 int ret = delayed_slow_work_enqueue(&myitem, my_jiffy_delay);
121
122
123The items are reference counted, so there ought to be no need for a flush
124operation. But as the reference counting is optional, means to cancel
125existing work items are also included:
126
127 cancel_slow_work(&myitem);
128 cancel_delayed_slow_work(&myitem);
129
130can be used to cancel pending work. The above cancel function waits for
131existing work to have been executed (or prevent execution of them, depending
132on timing).
133
134
135When all a module's slow work items have been processed, and the
136module has no further interest in the facility, it should unregister its
137interest:
138
139 slow_work_unregister_user(struct module *module);
140
141The module pointer is used to wait for all outstanding work items for that
142module before completing the unregistration. This prevents the put_ref() code
143from being taken away before it completes. module should almost certainly be
144THIS_MODULE.
145
146
147================
148HELPER FUNCTIONS
149================
150
151The slow-work facility provides a function by which it can be determined
152whether or not an item is queued for later execution:
153
154 bool queued = slow_work_is_queued(struct slow_work *work);
155
156If it returns false, then the item is not on the queue (it may be executing
157with a requeue pending). This can be used to work out whether an item on which
158another depends is on the queue, thus allowing a dependent item to be queued
159after it.
160
161If the above shows an item on which another depends not to be queued, then the
162owner of the dependent item might need to wait. However, to avoid locking up
163the threads unnecessarily be sleeping in them, it can make sense under some
164circumstances to return the work item to the queue, thus deferring it until
165some other items have had a chance to make use of the yielded thread.
166
167To yield a thread and defer an item, the work function should simply enqueue
168the work item again and return. However, this doesn't work if there's nothing
169actually on the queue, as the thread just vacated will jump straight back into
170the item's work function, thus busy waiting on a CPU.
171
172Instead, the item should use the thread to wait for the dependency to go away,
173but rather than using schedule() or schedule_timeout() to sleep, it should use
174the following function:
175
176 bool requeue = slow_work_sleep_till_thread_needed(
177 struct slow_work *work,
178 signed long *_timeout);
179
180This will add a second wait and then sleep, such that it will be woken up if
181either something appears on the queue that could usefully make use of the
182thread - and behind which this item can be queued, or if the event the caller
183set up to wait for happens. True will be returned if something else appeared
184on the queue and this work function should perhaps return, of false if
185something else woke it up. The timeout is as for schedule_timeout().
186
187For example:
188
189 wq = bit_waitqueue(&my_flags, MY_BIT);
190 init_wait(&wait);
191 requeue = false;
192 do {
193 prepare_to_wait(wq, &wait, TASK_UNINTERRUPTIBLE);
194 if (!test_bit(MY_BIT, &my_flags))
195 break;
196 requeue = slow_work_sleep_till_thread_needed(&my_work,
197 &timeout);
198 } while (timeout > 0 && !requeue);
199 finish_wait(wq, &wait);
200 if (!test_bit(MY_BIT, &my_flags)
201 goto do_my_thing;
202 if (requeue)
203 return; // to slow_work
204
205
206===============
207ITEM OPERATIONS
208===============
209
210Each work item requires a table of operations of type struct slow_work_ops.
211Only ->execute() is required; the getting and putting of a reference and the
212describing of an item are all optional.
213
214 (*) Get a reference on an item:
215
216 int (*get_ref)(struct slow_work *work);
217
218 This allows the thread pool to attempt to pin an item by getting a
219 reference on it. This function should return 0 if the reference was
220 granted, or a -ve error otherwise. If an error is returned,
221 slow_work_enqueue() will fail.
222
223 The reference is held whilst the item is queued and whilst it is being
224 executed. The item may then be requeued with the same reference held, or
225 the reference will be released.
226
227 (*) Release a reference on an item:
228
229 void (*put_ref)(struct slow_work *work);
230
231 This allows the thread pool to unpin an item by releasing the reference on
232 it. The thread pool will not touch the item again once this has been
233 called.
234
235 (*) Execute an item:
236
237 void (*execute)(struct slow_work *work);
238
239 This should perform the work required of the item. It may sleep, it may
240 perform disk I/O and it may wait for locks.
241
242 (*) View an item through /proc:
243
244 void (*desc)(struct slow_work *work, struct seq_file *m);
245
246 If supplied, this should print to 'm' a small string describing the work
247 the item is to do. This should be no more than about 40 characters, and
248 shouldn't include a newline character.
249
250 See the 'Viewing executing and queued items' section below.
251
252
253==================
254POOL CONFIGURATION
255==================
256
257The slow-work thread pool has a number of configurables:
258
259 (*) /proc/sys/kernel/slow-work/min-threads
260
261 The minimum number of threads that should be in the pool whilst it is in
262 use. This may be anywhere between 2 and max-threads.
263
264 (*) /proc/sys/kernel/slow-work/max-threads
265
266 The maximum number of threads that should in the pool. This may be
267 anywhere between min-threads and 255 or NR_CPUS * 2, whichever is greater.
268
269 (*) /proc/sys/kernel/slow-work/vslow-percentage
270
271 The percentage of active threads in the pool that may be used to execute
272 very slow work items. This may be between 1 and 99. The resultant number
273 is bounded to between 1 and one fewer than the number of active threads.
274 This ensures there is always at least one thread that can process very
275 slow work items, and always at least one thread that won't.
276
277
278==================================
279VIEWING EXECUTING AND QUEUED ITEMS
280==================================
281
282If CONFIG_SLOW_WORK_DEBUG is enabled, a debugfs file is made available:
283
284 /sys/kernel/debug/slow_work/runqueue
285
286through which the list of work items being executed and the queues of items to
287be executed may be viewed. The owner of a work item is given the chance to
288add some information of its own.
289
290The contents look something like the following:
291
292 THR PID ITEM ADDR FL MARK DESC
293 === ===== ================ == ===== ==========
294 0 3005 ffff880023f52348 a 952ms FSC: OBJ17d3: LOOK
295 1 3006 ffff880024e33668 2 160ms FSC: OBJ17e5 OP60d3b: Write1/Store fl=2
296 2 3165 ffff8800296dd180 a 424ms FSC: OBJ17e4: LOOK
297 3 4089 ffff8800262c8d78 a 212ms FSC: OBJ17ea: CRTN
298 4 4090 ffff88002792bed8 2 388ms FSC: OBJ17e8 OP60d36: Write1/Store fl=2
299 5 4092 ffff88002a0ef308 2 388ms FSC: OBJ17e7 OP60d2e: Write1/Store fl=2
300 6 4094 ffff88002abaf4b8 2 132ms FSC: OBJ17e2 OP60d4e: Write1/Store fl=2
301 7 4095 ffff88002bb188e0 a 388ms FSC: OBJ17e9: CRTN
302 vsq - ffff880023d99668 1 308ms FSC: OBJ17e0 OP60f91: Write1/EnQ fl=2
303 vsq - ffff8800295d1740 1 212ms FSC: OBJ16be OP4d4b6: Write1/EnQ fl=2
304 vsq - ffff880025ba3308 1 160ms FSC: OBJ179a OP58dec: Write1/EnQ fl=2
305 vsq - ffff880024ec83e0 1 160ms FSC: OBJ17ae OP599f2: Write1/EnQ fl=2
306 vsq - ffff880026618e00 1 160ms FSC: OBJ17e6 OP60d33: Write1/EnQ fl=2
307 vsq - ffff880025a2a4b8 1 132ms FSC: OBJ16a2 OP4d583: Write1/EnQ fl=2
308 vsq - ffff880023cbe6d8 9 212ms FSC: OBJ17eb: LOOK
309 vsq - ffff880024d37590 9 212ms FSC: OBJ17ec: LOOK
310 vsq - ffff880027746cb0 9 212ms FSC: OBJ17ed: LOOK
311 vsq - ffff880024d37ae8 9 212ms FSC: OBJ17ee: LOOK
312 vsq - ffff880024d37cb0 9 212ms FSC: OBJ17ef: LOOK
313 vsq - ffff880025036550 9 212ms FSC: OBJ17f0: LOOK
314 vsq - ffff8800250368e0 9 212ms FSC: OBJ17f1: LOOK
315 vsq - ffff880025036aa8 9 212ms FSC: OBJ17f2: LOOK
316
317In the 'THR' column, executing items show the thread they're occupying and
318queued threads indicate which queue they're on. 'PID' shows the process ID of
319a slow-work thread that's executing something. 'FL' shows the work item flags.
320'MARK' indicates how long since an item was queued or began executing. Lastly,
321the 'DESC' column permits the owner of an item to give some information.
322
diff --git a/include/linux/slow-work.h b/include/linux/slow-work.h
deleted file mode 100644
index 13337bf6c3f5..000000000000
--- a/include/linux/slow-work.h
+++ /dev/null
@@ -1,163 +0,0 @@
1/* Worker thread pool for slow items, such as filesystem lookups or mkdirs
2 *
3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 *
11 * See Documentation/slow-work.txt
12 */
13
14#ifndef _LINUX_SLOW_WORK_H
15#define _LINUX_SLOW_WORK_H
16
17#ifdef CONFIG_SLOW_WORK
18
19#include <linux/sysctl.h>
20#include <linux/timer.h>
21
22struct slow_work;
23#ifdef CONFIG_SLOW_WORK_DEBUG
24struct seq_file;
25#endif
26
27/*
28 * The operations used to support slow work items
29 */
30struct slow_work_ops {
31 /* owner */
32 struct module *owner;
33
34 /* get a ref on a work item
35 * - return 0 if successful, -ve if not
36 */
37 int (*get_ref)(struct slow_work *work);
38
39 /* discard a ref to a work item */
40 void (*put_ref)(struct slow_work *work);
41
42 /* execute a work item */
43 void (*execute)(struct slow_work *work);
44
45#ifdef CONFIG_SLOW_WORK_DEBUG
46 /* describe a work item for debugfs */
47 void (*desc)(struct slow_work *work, struct seq_file *m);
48#endif
49};
50
51/*
52 * A slow work item
53 * - A reference is held on the parent object by the thread pool when it is
54 * queued
55 */
56struct slow_work {
57 struct module *owner; /* the owning module */
58 unsigned long flags;
59#define SLOW_WORK_PENDING 0 /* item pending (further) execution */
60#define SLOW_WORK_EXECUTING 1 /* item currently executing */
61#define SLOW_WORK_ENQ_DEFERRED 2 /* item enqueue deferred */
62#define SLOW_WORK_VERY_SLOW 3 /* item is very slow */
63#define SLOW_WORK_CANCELLING 4 /* item is being cancelled, don't enqueue */
64#define SLOW_WORK_DELAYED 5 /* item is struct delayed_slow_work with active timer */
65 const struct slow_work_ops *ops; /* operations table for this item */
66 struct list_head link; /* link in queue */
67#ifdef CONFIG_SLOW_WORK_DEBUG
68 struct timespec mark; /* jiffies at which queued or exec begun */
69#endif
70};
71
72struct delayed_slow_work {
73 struct slow_work work;
74 struct timer_list timer;
75};
76
77/**
78 * slow_work_init - Initialise a slow work item
79 * @work: The work item to initialise
80 * @ops: The operations to use to handle the slow work item
81 *
82 * Initialise a slow work item.
83 */
84static inline void slow_work_init(struct slow_work *work,
85 const struct slow_work_ops *ops)
86{
87 work->flags = 0;
88 work->ops = ops;
89 INIT_LIST_HEAD(&work->link);
90}
91
92/**
93 * slow_work_init - Initialise a delayed slow work item
94 * @work: The work item to initialise
95 * @ops: The operations to use to handle the slow work item
96 *
97 * Initialise a delayed slow work item.
98 */
99static inline void delayed_slow_work_init(struct delayed_slow_work *dwork,
100 const struct slow_work_ops *ops)
101{
102 init_timer(&dwork->timer);
103 slow_work_init(&dwork->work, ops);
104}
105
106/**
107 * vslow_work_init - Initialise a very slow work item
108 * @work: The work item to initialise
109 * @ops: The operations to use to handle the slow work item
110 *
111 * Initialise a very slow work item. This item will be restricted such that
112 * only a certain number of the pool threads will be able to execute items of
113 * this type.
114 */
115static inline void vslow_work_init(struct slow_work *work,
116 const struct slow_work_ops *ops)
117{
118 work->flags = 1 << SLOW_WORK_VERY_SLOW;
119 work->ops = ops;
120 INIT_LIST_HEAD(&work->link);
121}
122
123/**
124 * slow_work_is_queued - Determine if a slow work item is on the work queue
125 * work: The work item to test
126 *
127 * Determine if the specified slow-work item is on the work queue. This
128 * returns true if it is actually on the queue.
129 *
130 * If the item is executing and has been marked for requeue when execution
131 * finishes, then false will be returned.
132 *
133 * Anyone wishing to wait for completion of execution can wait on the
134 * SLOW_WORK_EXECUTING bit.
135 */
136static inline bool slow_work_is_queued(struct slow_work *work)
137{
138 unsigned long flags = work->flags;
139 return flags & SLOW_WORK_PENDING && !(flags & SLOW_WORK_EXECUTING);
140}
141
142extern int slow_work_enqueue(struct slow_work *work);
143extern void slow_work_cancel(struct slow_work *work);
144extern int slow_work_register_user(struct module *owner);
145extern void slow_work_unregister_user(struct module *owner);
146
147extern int delayed_slow_work_enqueue(struct delayed_slow_work *dwork,
148 unsigned long delay);
149
150static inline void delayed_slow_work_cancel(struct delayed_slow_work *dwork)
151{
152 slow_work_cancel(&dwork->work);
153}
154
155extern bool slow_work_sleep_till_thread_needed(struct slow_work *work,
156 signed long *_timeout);
157
158#ifdef CONFIG_SYSCTL
159extern ctl_table slow_work_sysctls[];
160#endif
161
162#endif /* CONFIG_SLOW_WORK */
163#endif /* _LINUX_SLOW_WORK_H */
diff --git a/init/Kconfig b/init/Kconfig
index 5cff9a980c39..cb64c5889e02 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1143,30 +1143,6 @@ config TRACEPOINTS
1143 1143
1144source "arch/Kconfig" 1144source "arch/Kconfig"
1145 1145
1146config SLOW_WORK
1147 default n
1148 bool
1149 help
1150 The slow work thread pool provides a number of dynamically allocated
1151 threads that can be used by the kernel to perform operations that
1152 take a relatively long time.
1153
1154 An example of this would be CacheFiles doing a path lookup followed
1155 by a series of mkdirs and a create call, all of which have to touch
1156 disk.
1157
1158 See Documentation/slow-work.txt.
1159
1160config SLOW_WORK_DEBUG
1161 bool "Slow work debugging through debugfs"
1162 default n
1163 depends on SLOW_WORK && DEBUG_FS
1164 help
1165 Display the contents of the slow work run queue through debugfs,
1166 including items currently executing.
1167
1168 See Documentation/slow-work.txt.
1169
1170endmenu # General setup 1146endmenu # General setup
1171 1147
1172config HAVE_GENERIC_DMA_COHERENT 1148config HAVE_GENERIC_DMA_COHERENT
diff --git a/kernel/Makefile b/kernel/Makefile
index 057472fbc272..2484ac39b2e2 100644
--- a/kernel/Makefile
+++ b/kernel/Makefile
@@ -99,8 +99,6 @@ obj-$(CONFIG_TRACING) += trace/
99obj-$(CONFIG_X86_DS) += trace/ 99obj-$(CONFIG_X86_DS) += trace/
100obj-$(CONFIG_RING_BUFFER) += trace/ 100obj-$(CONFIG_RING_BUFFER) += trace/
101obj-$(CONFIG_SMP) += sched_cpupri.o 101obj-$(CONFIG_SMP) += sched_cpupri.o
102obj-$(CONFIG_SLOW_WORK) += slow-work.o
103obj-$(CONFIG_SLOW_WORK_DEBUG) += slow-work-debugfs.o
104obj-$(CONFIG_PERF_EVENTS) += perf_event.o 102obj-$(CONFIG_PERF_EVENTS) += perf_event.o
105obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o 103obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
106obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o 104obj-$(CONFIG_USER_RETURN_NOTIFIER) += user-return-notifier.o
diff --git a/kernel/slow-work-debugfs.c b/kernel/slow-work-debugfs.c
deleted file mode 100644
index e45c43645298..000000000000
--- a/kernel/slow-work-debugfs.c
+++ /dev/null
@@ -1,227 +0,0 @@
1/* Slow work debugging
2 *
3 * Copyright (C) 2009 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/module.h>
13#include <linux/slow-work.h>
14#include <linux/fs.h>
15#include <linux/time.h>
16#include <linux/seq_file.h>
17#include "slow-work.h"
18
19#define ITERATOR_SHIFT (BITS_PER_LONG - 4)
20#define ITERATOR_SELECTOR (0xfUL << ITERATOR_SHIFT)
21#define ITERATOR_COUNTER (~ITERATOR_SELECTOR)
22
23void slow_work_new_thread_desc(struct slow_work *work, struct seq_file *m)
24{
25 seq_puts(m, "Slow-work: New thread");
26}
27
28/*
29 * Render the time mark field on a work item into a 5-char time with units plus
30 * a space
31 */
32static void slow_work_print_mark(struct seq_file *m, struct slow_work *work)
33{
34 struct timespec now, diff;
35
36 now = CURRENT_TIME;
37 diff = timespec_sub(now, work->mark);
38
39 if (diff.tv_sec < 0)
40 seq_puts(m, " -ve ");
41 else if (diff.tv_sec == 0 && diff.tv_nsec < 1000)
42 seq_printf(m, "%3luns ", diff.tv_nsec);
43 else if (diff.tv_sec == 0 && diff.tv_nsec < 1000000)
44 seq_printf(m, "%3luus ", diff.tv_nsec / 1000);
45 else if (diff.tv_sec == 0 && diff.tv_nsec < 1000000000)
46 seq_printf(m, "%3lums ", diff.tv_nsec / 1000000);
47 else if (diff.tv_sec <= 1)
48 seq_puts(m, " 1s ");
49 else if (diff.tv_sec < 60)
50 seq_printf(m, "%4lus ", diff.tv_sec);
51 else if (diff.tv_sec < 60 * 60)
52 seq_printf(m, "%4lum ", diff.tv_sec / 60);
53 else if (diff.tv_sec < 60 * 60 * 24)
54 seq_printf(m, "%4luh ", diff.tv_sec / 3600);
55 else
56 seq_puts(m, "exces ");
57}
58
59/*
60 * Describe a slow work item for debugfs
61 */
62static int slow_work_runqueue_show(struct seq_file *m, void *v)
63{
64 struct slow_work *work;
65 struct list_head *p = v;
66 unsigned long id;
67
68 switch ((unsigned long) v) {
69 case 1:
70 seq_puts(m, "THR PID ITEM ADDR FL MARK DESC\n");
71 return 0;
72 case 2:
73 seq_puts(m, "=== ===== ================ == ===== ==========\n");
74 return 0;
75
76 case 3 ... 3 + SLOW_WORK_THREAD_LIMIT - 1:
77 id = (unsigned long) v - 3;
78
79 read_lock(&slow_work_execs_lock);
80 work = slow_work_execs[id];
81 if (work) {
82 smp_read_barrier_depends();
83
84 seq_printf(m, "%3lu %5d %16p %2lx ",
85 id, slow_work_pids[id], work, work->flags);
86 slow_work_print_mark(m, work);
87
88 if (work->ops->desc)
89 work->ops->desc(work, m);
90 seq_putc(m, '\n');
91 }
92 read_unlock(&slow_work_execs_lock);
93 return 0;
94
95 default:
96 work = list_entry(p, struct slow_work, link);
97 seq_printf(m, "%3s - %16p %2lx ",
98 work->flags & SLOW_WORK_VERY_SLOW ? "vsq" : "sq",
99 work, work->flags);
100 slow_work_print_mark(m, work);
101
102 if (work->ops->desc)
103 work->ops->desc(work, m);
104 seq_putc(m, '\n');
105 return 0;
106 }
107}
108
109/*
110 * map the iterator to a work item
111 */
112static void *slow_work_runqueue_index(struct seq_file *m, loff_t *_pos)
113{
114 struct list_head *p;
115 unsigned long count, id;
116
117 switch (*_pos >> ITERATOR_SHIFT) {
118 case 0x0:
119 if (*_pos == 0)
120 *_pos = 1;
121 if (*_pos < 3)
122 return (void *)(unsigned long) *_pos;
123 if (*_pos < 3 + SLOW_WORK_THREAD_LIMIT)
124 for (id = *_pos - 3;
125 id < SLOW_WORK_THREAD_LIMIT;
126 id++, (*_pos)++)
127 if (slow_work_execs[id])
128 return (void *)(unsigned long) *_pos;
129 *_pos = 0x1UL << ITERATOR_SHIFT;
130
131 case 0x1:
132 count = *_pos & ITERATOR_COUNTER;
133 list_for_each(p, &slow_work_queue) {
134 if (count == 0)
135 return p;
136 count--;
137 }
138 *_pos = 0x2UL << ITERATOR_SHIFT;
139
140 case 0x2:
141 count = *_pos & ITERATOR_COUNTER;
142 list_for_each(p, &vslow_work_queue) {
143 if (count == 0)
144 return p;
145 count--;
146 }
147 *_pos = 0x3UL << ITERATOR_SHIFT;
148
149 default:
150 return NULL;
151 }
152}
153
154/*
155 * set up the iterator to start reading from the first line
156 */
157static void *slow_work_runqueue_start(struct seq_file *m, loff_t *_pos)
158{
159 spin_lock_irq(&slow_work_queue_lock);
160 return slow_work_runqueue_index(m, _pos);
161}
162
163/*
164 * move to the next line
165 */
166static void *slow_work_runqueue_next(struct seq_file *m, void *v, loff_t *_pos)
167{
168 struct list_head *p = v;
169 unsigned long selector = *_pos >> ITERATOR_SHIFT;
170
171 (*_pos)++;
172 switch (selector) {
173 case 0x0:
174 return slow_work_runqueue_index(m, _pos);
175
176 case 0x1:
177 if (*_pos >> ITERATOR_SHIFT == 0x1) {
178 p = p->next;
179 if (p != &slow_work_queue)
180 return p;
181 }
182 *_pos = 0x2UL << ITERATOR_SHIFT;
183 p = &vslow_work_queue;
184
185 case 0x2:
186 if (*_pos >> ITERATOR_SHIFT == 0x2) {
187 p = p->next;
188 if (p != &vslow_work_queue)
189 return p;
190 }
191 *_pos = 0x3UL << ITERATOR_SHIFT;
192
193 default:
194 return NULL;
195 }
196}
197
198/*
199 * clean up after reading
200 */
201static void slow_work_runqueue_stop(struct seq_file *m, void *v)
202{
203 spin_unlock_irq(&slow_work_queue_lock);
204}
205
206static const struct seq_operations slow_work_runqueue_ops = {
207 .start = slow_work_runqueue_start,
208 .stop = slow_work_runqueue_stop,
209 .next = slow_work_runqueue_next,
210 .show = slow_work_runqueue_show,
211};
212
213/*
214 * open "/sys/kernel/debug/slow_work/runqueue" to list queue contents
215 */
216static int slow_work_runqueue_open(struct inode *inode, struct file *file)
217{
218 return seq_open(file, &slow_work_runqueue_ops);
219}
220
221const struct file_operations slow_work_runqueue_fops = {
222 .owner = THIS_MODULE,
223 .open = slow_work_runqueue_open,
224 .read = seq_read,
225 .llseek = seq_lseek,
226 .release = seq_release,
227};
diff --git a/kernel/slow-work.c b/kernel/slow-work.c
deleted file mode 100644
index 7d3f4fa9ef4f..000000000000
--- a/kernel/slow-work.c
+++ /dev/null
@@ -1,1068 +0,0 @@
1/* Worker thread pool for slow items, such as filesystem lookups or mkdirs
2 *
3 * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 *
11 * See Documentation/slow-work.txt
12 */
13
14#include <linux/module.h>
15#include <linux/slow-work.h>
16#include <linux/kthread.h>
17#include <linux/freezer.h>
18#include <linux/wait.h>
19#include <linux/debugfs.h>
20#include "slow-work.h"
21
22static void slow_work_cull_timeout(unsigned long);
23static void slow_work_oom_timeout(unsigned long);
24
25#ifdef CONFIG_SYSCTL
26static int slow_work_min_threads_sysctl(struct ctl_table *, int,
27 void __user *, size_t *, loff_t *);
28
29static int slow_work_max_threads_sysctl(struct ctl_table *, int ,
30 void __user *, size_t *, loff_t *);
31#endif
32
33/*
34 * The pool of threads has at least min threads in it as long as someone is
35 * using the facility, and may have as many as max.
36 *
37 * A portion of the pool may be processing very slow operations.
38 */
39static unsigned slow_work_min_threads = 2;
40static unsigned slow_work_max_threads = 4;
41static unsigned vslow_work_proportion = 50; /* % of threads that may process
42 * very slow work */
43
44#ifdef CONFIG_SYSCTL
45static const int slow_work_min_min_threads = 2;
46static int slow_work_max_max_threads = SLOW_WORK_THREAD_LIMIT;
47static const int slow_work_min_vslow = 1;
48static const int slow_work_max_vslow = 99;
49
50ctl_table slow_work_sysctls[] = {
51 {
52 .procname = "min-threads",
53 .data = &slow_work_min_threads,
54 .maxlen = sizeof(unsigned),
55 .mode = 0644,
56 .proc_handler = slow_work_min_threads_sysctl,
57 .extra1 = (void *) &slow_work_min_min_threads,
58 .extra2 = &slow_work_max_threads,
59 },
60 {
61 .procname = "max-threads",
62 .data = &slow_work_max_threads,
63 .maxlen = sizeof(unsigned),
64 .mode = 0644,
65 .proc_handler = slow_work_max_threads_sysctl,
66 .extra1 = &slow_work_min_threads,
67 .extra2 = (void *) &slow_work_max_max_threads,
68 },
69 {
70 .procname = "vslow-percentage",
71 .data = &vslow_work_proportion,
72 .maxlen = sizeof(unsigned),
73 .mode = 0644,
74 .proc_handler = proc_dointvec_minmax,
75 .extra1 = (void *) &slow_work_min_vslow,
76 .extra2 = (void *) &slow_work_max_vslow,
77 },
78 {}
79};
80#endif
81
82/*
83 * The active state of the thread pool
84 */
85static atomic_t slow_work_thread_count;
86static atomic_t vslow_work_executing_count;
87
88static bool slow_work_may_not_start_new_thread;
89static bool slow_work_cull; /* cull a thread due to lack of activity */
90static DEFINE_TIMER(slow_work_cull_timer, slow_work_cull_timeout, 0, 0);
91static DEFINE_TIMER(slow_work_oom_timer, slow_work_oom_timeout, 0, 0);
92static struct slow_work slow_work_new_thread; /* new thread starter */
93
94/*
95 * slow work ID allocation (use slow_work_queue_lock)
96 */
97static DECLARE_BITMAP(slow_work_ids, SLOW_WORK_THREAD_LIMIT);
98
99/*
100 * Unregistration tracking to prevent put_ref() from disappearing during module
101 * unload
102 */
103#ifdef CONFIG_MODULES
104static struct module *slow_work_thread_processing[SLOW_WORK_THREAD_LIMIT];
105static struct module *slow_work_unreg_module;
106static struct slow_work *slow_work_unreg_work_item;
107static DECLARE_WAIT_QUEUE_HEAD(slow_work_unreg_wq);
108static DEFINE_MUTEX(slow_work_unreg_sync_lock);
109
110static void slow_work_set_thread_processing(int id, struct slow_work *work)
111{
112 if (work)
113 slow_work_thread_processing[id] = work->owner;
114}
115static void slow_work_done_thread_processing(int id, struct slow_work *work)
116{
117 struct module *module = slow_work_thread_processing[id];
118
119 slow_work_thread_processing[id] = NULL;
120 smp_mb();
121 if (slow_work_unreg_work_item == work ||
122 slow_work_unreg_module == module)
123 wake_up_all(&slow_work_unreg_wq);
124}
125static void slow_work_clear_thread_processing(int id)
126{
127 slow_work_thread_processing[id] = NULL;
128}
129#else
130static void slow_work_set_thread_processing(int id, struct slow_work *work) {}
131static void slow_work_done_thread_processing(int id, struct slow_work *work) {}
132static void slow_work_clear_thread_processing(int id) {}
133#endif
134
135/*
136 * Data for tracking currently executing items for indication through /proc
137 */
138#ifdef CONFIG_SLOW_WORK_DEBUG
139struct slow_work *slow_work_execs[SLOW_WORK_THREAD_LIMIT];
140pid_t slow_work_pids[SLOW_WORK_THREAD_LIMIT];
141DEFINE_RWLOCK(slow_work_execs_lock);
142#endif
143
144/*
145 * The queues of work items and the lock governing access to them. These are
146 * shared between all the CPUs. It doesn't make sense to have per-CPU queues
147 * as the number of threads bears no relation to the number of CPUs.
148 *
149 * There are two queues of work items: one for slow work items, and one for
150 * very slow work items.
151 */
152LIST_HEAD(slow_work_queue);
153LIST_HEAD(vslow_work_queue);
154DEFINE_SPINLOCK(slow_work_queue_lock);
155
156/*
157 * The following are two wait queues that get pinged when a work item is placed
158 * on an empty queue. These allow work items that are hogging a thread by
159 * sleeping in a way that could be deferred to yield their thread and enqueue
160 * themselves.
161 */
162static DECLARE_WAIT_QUEUE_HEAD(slow_work_queue_waits_for_occupation);
163static DECLARE_WAIT_QUEUE_HEAD(vslow_work_queue_waits_for_occupation);
164
165/*
166 * The thread controls. A variable used to signal to the threads that they
167 * should exit when the queue is empty, a waitqueue used by the threads to wait
168 * for signals, and a completion set by the last thread to exit.
169 */
170static bool slow_work_threads_should_exit;
171static DECLARE_WAIT_QUEUE_HEAD(slow_work_thread_wq);
172static DECLARE_COMPLETION(slow_work_last_thread_exited);
173
174/*
175 * The number of users of the thread pool and its lock. Whilst this is zero we
176 * have no threads hanging around, and when this reaches zero, we wait for all
177 * active or queued work items to complete and kill all the threads we do have.
178 */
179static int slow_work_user_count;
180static DEFINE_MUTEX(slow_work_user_lock);
181
182static inline int slow_work_get_ref(struct slow_work *work)
183{
184 if (work->ops->get_ref)
185 return work->ops->get_ref(work);
186
187 return 0;
188}
189
190static inline void slow_work_put_ref(struct slow_work *work)
191{
192 if (work->ops->put_ref)
193 work->ops->put_ref(work);
194}
195
196/*
197 * Calculate the maximum number of active threads in the pool that are
198 * permitted to process very slow work items.
199 *
200 * The answer is rounded up to at least 1, but may not equal or exceed the
201 * maximum number of the threads in the pool. This means we always have at
202 * least one thread that can process slow work items, and we always have at
203 * least one thread that won't get tied up doing so.
204 */
205static unsigned slow_work_calc_vsmax(void)
206{
207 unsigned vsmax;
208
209 vsmax = atomic_read(&slow_work_thread_count) * vslow_work_proportion;
210 vsmax /= 100;
211 vsmax = max(vsmax, 1U);
212 return min(vsmax, slow_work_max_threads - 1);
213}
214
215/*
216 * Attempt to execute stuff queued on a slow thread. Return true if we managed
217 * it, false if there was nothing to do.
218 */
219static noinline bool slow_work_execute(int id)
220{
221 struct slow_work *work = NULL;
222 unsigned vsmax;
223 bool very_slow;
224
225 vsmax = slow_work_calc_vsmax();
226
227 /* see if we can schedule a new thread to be started if we're not
228 * keeping up with the work */
229 if (!waitqueue_active(&slow_work_thread_wq) &&
230 (!list_empty(&slow_work_queue) || !list_empty(&vslow_work_queue)) &&
231 atomic_read(&slow_work_thread_count) < slow_work_max_threads &&
232 !slow_work_may_not_start_new_thread)
233 slow_work_enqueue(&slow_work_new_thread);
234
235 /* find something to execute */
236 spin_lock_irq(&slow_work_queue_lock);
237 if (!list_empty(&vslow_work_queue) &&
238 atomic_read(&vslow_work_executing_count) < vsmax) {
239 work = list_entry(vslow_work_queue.next,
240 struct slow_work, link);
241 if (test_and_set_bit_lock(SLOW_WORK_EXECUTING, &work->flags))
242 BUG();
243 list_del_init(&work->link);
244 atomic_inc(&vslow_work_executing_count);
245 very_slow = true;
246 } else if (!list_empty(&slow_work_queue)) {
247 work = list_entry(slow_work_queue.next,
248 struct slow_work, link);
249 if (test_and_set_bit_lock(SLOW_WORK_EXECUTING, &work->flags))
250 BUG();
251 list_del_init(&work->link);
252 very_slow = false;
253 } else {
254 very_slow = false; /* avoid the compiler warning */
255 }
256
257 slow_work_set_thread_processing(id, work);
258 if (work) {
259 slow_work_mark_time(work);
260 slow_work_begin_exec(id, work);
261 }
262
263 spin_unlock_irq(&slow_work_queue_lock);
264
265 if (!work)
266 return false;
267
268 if (!test_and_clear_bit(SLOW_WORK_PENDING, &work->flags))
269 BUG();
270
271 /* don't execute if the work is in the process of being cancelled */
272 if (!test_bit(SLOW_WORK_CANCELLING, &work->flags))
273 work->ops->execute(work);
274
275 if (very_slow)
276 atomic_dec(&vslow_work_executing_count);
277 clear_bit_unlock(SLOW_WORK_EXECUTING, &work->flags);
278
279 /* wake up anyone waiting for this work to be complete */
280 wake_up_bit(&work->flags, SLOW_WORK_EXECUTING);
281
282 slow_work_end_exec(id, work);
283
284 /* if someone tried to enqueue the item whilst we were executing it,
285 * then it'll be left unenqueued to avoid multiple threads trying to
286 * execute it simultaneously
287 *
288 * there is, however, a race between us testing the pending flag and
289 * getting the spinlock, and between the enqueuer setting the pending
290 * flag and getting the spinlock, so we use a deferral bit to tell us
291 * if the enqueuer got there first
292 */
293 if (test_bit(SLOW_WORK_PENDING, &work->flags)) {
294 spin_lock_irq(&slow_work_queue_lock);
295
296 if (!test_bit(SLOW_WORK_EXECUTING, &work->flags) &&
297 test_and_clear_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags))
298 goto auto_requeue;
299
300 spin_unlock_irq(&slow_work_queue_lock);
301 }
302
303 /* sort out the race between module unloading and put_ref() */
304 slow_work_put_ref(work);
305 slow_work_done_thread_processing(id, work);
306
307 return true;
308
309auto_requeue:
310 /* we must complete the enqueue operation
311 * - we transfer our ref on the item back to the appropriate queue
312 * - don't wake another thread up as we're awake already
313 */
314 slow_work_mark_time(work);
315 if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags))
316 list_add_tail(&work->link, &vslow_work_queue);
317 else
318 list_add_tail(&work->link, &slow_work_queue);
319 spin_unlock_irq(&slow_work_queue_lock);
320 slow_work_clear_thread_processing(id);
321 return true;
322}
323
324/**
325 * slow_work_sleep_till_thread_needed - Sleep till thread needed by other work
326 * work: The work item under execution that wants to sleep
327 * _timeout: Scheduler sleep timeout
328 *
329 * Allow a requeueable work item to sleep on a slow-work processor thread until
330 * that thread is needed to do some other work or the sleep is interrupted by
331 * some other event.
332 *
333 * The caller must set up a wake up event before calling this and must have set
334 * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
335 * condition before calling this function as no test is made here.
336 *
337 * False is returned if there is nothing on the queue; true is returned if the
338 * work item should be requeued
339 */
340bool slow_work_sleep_till_thread_needed(struct slow_work *work,
341 signed long *_timeout)
342{
343 wait_queue_head_t *wfo_wq;
344 struct list_head *queue;
345
346 DEFINE_WAIT(wait);
347
348 if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) {
349 wfo_wq = &vslow_work_queue_waits_for_occupation;
350 queue = &vslow_work_queue;
351 } else {
352 wfo_wq = &slow_work_queue_waits_for_occupation;
353 queue = &slow_work_queue;
354 }
355
356 if (!list_empty(queue))
357 return true;
358
359 add_wait_queue_exclusive(wfo_wq, &wait);
360 if (list_empty(queue))
361 *_timeout = schedule_timeout(*_timeout);
362 finish_wait(wfo_wq, &wait);
363
364 return !list_empty(queue);
365}
366EXPORT_SYMBOL(slow_work_sleep_till_thread_needed);
367
368/**
369 * slow_work_enqueue - Schedule a slow work item for processing
370 * @work: The work item to queue
371 *
372 * Schedule a slow work item for processing. If the item is already undergoing
373 * execution, this guarantees not to re-enter the execution routine until the
374 * first execution finishes.
375 *
376 * The item is pinned by this function as it retains a reference to it, managed
377 * through the item operations. The item is unpinned once it has been
378 * executed.
379 *
380 * An item may hog the thread that is running it for a relatively large amount
381 * of time, sufficient, for example, to perform several lookup, mkdir, create
382 * and setxattr operations. It may sleep on I/O and may sleep to obtain locks.
383 *
384 * Conversely, if a number of items are awaiting processing, it may take some
385 * time before any given item is given attention. The number of threads in the
386 * pool may be increased to deal with demand, but only up to a limit.
387 *
388 * If SLOW_WORK_VERY_SLOW is set on the work item, then it will be placed in
389 * the very slow queue, from which only a portion of the threads will be
390 * allowed to pick items to execute. This ensures that very slow items won't
391 * overly block ones that are just ordinarily slow.
392 *
393 * Returns 0 if successful, -EAGAIN if not (or -ECANCELED if cancelled work is
394 * attempted queued)
395 */
396int slow_work_enqueue(struct slow_work *work)
397{
398 wait_queue_head_t *wfo_wq;
399 struct list_head *queue;
400 unsigned long flags;
401 int ret;
402
403 if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
404 return -ECANCELED;
405
406 BUG_ON(slow_work_user_count <= 0);
407 BUG_ON(!work);
408 BUG_ON(!work->ops);
409
410 /* when honouring an enqueue request, we only promise that we will run
411 * the work function in the future; we do not promise to run it once
412 * per enqueue request
413 *
414 * we use the PENDING bit to merge together repeat requests without
415 * having to disable IRQs and take the spinlock, whilst still
416 * maintaining our promise
417 */
418 if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) {
419 if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) {
420 wfo_wq = &vslow_work_queue_waits_for_occupation;
421 queue = &vslow_work_queue;
422 } else {
423 wfo_wq = &slow_work_queue_waits_for_occupation;
424 queue = &slow_work_queue;
425 }
426
427 spin_lock_irqsave(&slow_work_queue_lock, flags);
428
429 if (unlikely(test_bit(SLOW_WORK_CANCELLING, &work->flags)))
430 goto cancelled;
431
432 /* we promise that we will not attempt to execute the work
433 * function in more than one thread simultaneously
434 *
435 * this, however, leaves us with a problem if we're asked to
436 * enqueue the work whilst someone is executing the work
437 * function as simply queueing the work immediately means that
438 * another thread may try executing it whilst it is already
439 * under execution
440 *
441 * to deal with this, we set the ENQ_DEFERRED bit instead of
442 * enqueueing, and the thread currently executing the work
443 * function will enqueue the work item when the work function
444 * returns and it has cleared the EXECUTING bit
445 */
446 if (test_bit(SLOW_WORK_EXECUTING, &work->flags)) {
447 set_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags);
448 } else {
449 ret = slow_work_get_ref(work);
450 if (ret < 0)
451 goto failed;
452 slow_work_mark_time(work);
453 list_add_tail(&work->link, queue);
454 wake_up(&slow_work_thread_wq);
455
456 /* if someone who could be requeued is sleeping on a
457 * thread, then ask them to yield their thread */
458 if (work->link.prev == queue)
459 wake_up(wfo_wq);
460 }
461
462 spin_unlock_irqrestore(&slow_work_queue_lock, flags);
463 }
464 return 0;
465
466cancelled:
467 ret = -ECANCELED;
468failed:
469 spin_unlock_irqrestore(&slow_work_queue_lock, flags);
470 return ret;
471}
472EXPORT_SYMBOL(slow_work_enqueue);
473
474static int slow_work_wait(void *word)
475{
476 schedule();
477 return 0;
478}
479
480/**
481 * slow_work_cancel - Cancel a slow work item
482 * @work: The work item to cancel
483 *
484 * This function will cancel a previously enqueued work item. If we cannot
485 * cancel the work item, it is guarenteed to have run when this function
486 * returns.
487 */
488void slow_work_cancel(struct slow_work *work)
489{
490 bool wait = true, put = false;
491
492 set_bit(SLOW_WORK_CANCELLING, &work->flags);
493 smp_mb();
494
495 /* if the work item is a delayed work item with an active timer, we
496 * need to wait for the timer to finish _before_ getting the spinlock,
497 * lest we deadlock against the timer routine
498 *
499 * the timer routine will leave DELAYED set if it notices the
500 * CANCELLING flag in time
501 */
502 if (test_bit(SLOW_WORK_DELAYED, &work->flags)) {
503 struct delayed_slow_work *dwork =
504 container_of(work, struct delayed_slow_work, work);
505 del_timer_sync(&dwork->timer);
506 }
507
508 spin_lock_irq(&slow_work_queue_lock);
509
510 if (test_bit(SLOW_WORK_DELAYED, &work->flags)) {
511 /* the timer routine aborted or never happened, so we are left
512 * holding the timer's reference on the item and should just
513 * drop the pending flag and wait for any ongoing execution to
514 * finish */
515 struct delayed_slow_work *dwork =
516 container_of(work, struct delayed_slow_work, work);
517
518 BUG_ON(timer_pending(&dwork->timer));
519 BUG_ON(!list_empty(&work->link));
520
521 clear_bit(SLOW_WORK_DELAYED, &work->flags);
522 put = true;
523 clear_bit(SLOW_WORK_PENDING, &work->flags);
524
525 } else if (test_bit(SLOW_WORK_PENDING, &work->flags) &&
526 !list_empty(&work->link)) {
527 /* the link in the pending queue holds a reference on the item
528 * that we will need to release */
529 list_del_init(&work->link);
530 wait = false;
531 put = true;
532 clear_bit(SLOW_WORK_PENDING, &work->flags);
533
534 } else if (test_and_clear_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags)) {
535 /* the executor is holding our only reference on the item, so
536 * we merely need to wait for it to finish executing */
537 clear_bit(SLOW_WORK_PENDING, &work->flags);
538 }
539
540 spin_unlock_irq(&slow_work_queue_lock);
541
542 /* the EXECUTING flag is set by the executor whilst the spinlock is set
543 * and before the item is dequeued - so assuming the above doesn't
544 * actually dequeue it, simply waiting for the EXECUTING flag to be
545 * released here should be sufficient */
546 if (wait)
547 wait_on_bit(&work->flags, SLOW_WORK_EXECUTING, slow_work_wait,
548 TASK_UNINTERRUPTIBLE);
549
550 clear_bit(SLOW_WORK_CANCELLING, &work->flags);
551 if (put)
552 slow_work_put_ref(work);
553}
554EXPORT_SYMBOL(slow_work_cancel);
555
556/*
557 * Handle expiry of the delay timer, indicating that a delayed slow work item
558 * should now be queued if not cancelled
559 */
560static void delayed_slow_work_timer(unsigned long data)
561{
562 wait_queue_head_t *wfo_wq;
563 struct list_head *queue;
564 struct slow_work *work = (struct slow_work *) data;
565 unsigned long flags;
566 bool queued = false, put = false, first = false;
567
568 if (test_bit(SLOW_WORK_VERY_SLOW, &work->flags)) {
569 wfo_wq = &vslow_work_queue_waits_for_occupation;
570 queue = &vslow_work_queue;
571 } else {
572 wfo_wq = &slow_work_queue_waits_for_occupation;
573 queue = &slow_work_queue;
574 }
575
576 spin_lock_irqsave(&slow_work_queue_lock, flags);
577 if (likely(!test_bit(SLOW_WORK_CANCELLING, &work->flags))) {
578 clear_bit(SLOW_WORK_DELAYED, &work->flags);
579
580 if (test_bit(SLOW_WORK_EXECUTING, &work->flags)) {
581 /* we discard the reference the timer was holding in
582 * favour of the one the executor holds */
583 set_bit(SLOW_WORK_ENQ_DEFERRED, &work->flags);
584 put = true;
585 } else {
586 slow_work_mark_time(work);
587 list_add_tail(&work->link, queue);
588 queued = true;
589 if (work->link.prev == queue)
590 first = true;
591 }
592 }
593
594 spin_unlock_irqrestore(&slow_work_queue_lock, flags);
595 if (put)
596 slow_work_put_ref(work);
597 if (first)
598 wake_up(wfo_wq);
599 if (queued)
600 wake_up(&slow_work_thread_wq);
601}
602
603/**
604 * delayed_slow_work_enqueue - Schedule a delayed slow work item for processing
605 * @dwork: The delayed work item to queue
606 * @delay: When to start executing the work, in jiffies from now
607 *
608 * This is similar to slow_work_enqueue(), but it adds a delay before the work
609 * is actually queued for processing.
610 *
611 * The item can have delayed processing requested on it whilst it is being
612 * executed. The delay will begin immediately, and if it expires before the
613 * item finishes executing, the item will be placed back on the queue when it
614 * has done executing.
615 */
616int delayed_slow_work_enqueue(struct delayed_slow_work *dwork,
617 unsigned long delay)
618{
619 struct slow_work *work = &dwork->work;
620 unsigned long flags;
621 int ret;
622
623 if (delay == 0)
624 return slow_work_enqueue(&dwork->work);
625
626 BUG_ON(slow_work_user_count <= 0);
627 BUG_ON(!work);
628 BUG_ON(!work->ops);
629
630 if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
631 return -ECANCELED;
632
633 if (!test_and_set_bit_lock(SLOW_WORK_PENDING, &work->flags)) {
634 spin_lock_irqsave(&slow_work_queue_lock, flags);
635
636 if (test_bit(SLOW_WORK_CANCELLING, &work->flags))
637 goto cancelled;
638
639 /* the timer holds a reference whilst it is pending */
640 ret = slow_work_get_ref(work);
641 if (ret < 0)
642 goto cant_get_ref;
643
644 if (test_and_set_bit(SLOW_WORK_DELAYED, &work->flags))
645 BUG();
646 dwork->timer.expires = jiffies + delay;
647 dwork->timer.data = (unsigned long) work;
648 dwork->timer.function = delayed_slow_work_timer;
649 add_timer(&dwork->timer);
650
651 spin_unlock_irqrestore(&slow_work_queue_lock, flags);
652 }
653
654 return 0;
655
656cancelled:
657 ret = -ECANCELED;
658cant_get_ref:
659 spin_unlock_irqrestore(&slow_work_queue_lock, flags);
660 return ret;
661}
662EXPORT_SYMBOL(delayed_slow_work_enqueue);
663
664/*
665 * Schedule a cull of the thread pool at some time in the near future
666 */
667static void slow_work_schedule_cull(void)
668{
669 mod_timer(&slow_work_cull_timer,
670 round_jiffies(jiffies + SLOW_WORK_CULL_TIMEOUT));
671}
672
673/*
674 * Worker thread culling algorithm
675 */
676static bool slow_work_cull_thread(void)
677{
678 unsigned long flags;
679 bool do_cull = false;
680
681 spin_lock_irqsave(&slow_work_queue_lock, flags);
682
683 if (slow_work_cull) {
684 slow_work_cull = false;
685
686 if (list_empty(&slow_work_queue) &&
687 list_empty(&vslow_work_queue) &&
688 atomic_read(&slow_work_thread_count) >
689 slow_work_min_threads) {
690 slow_work_schedule_cull();
691 do_cull = true;
692 }
693 }
694
695 spin_unlock_irqrestore(&slow_work_queue_lock, flags);
696 return do_cull;
697}
698
699/*
700 * Determine if there is slow work available for dispatch
701 */
702static inline bool slow_work_available(int vsmax)
703{
704 return !list_empty(&slow_work_queue) ||
705 (!list_empty(&vslow_work_queue) &&
706 atomic_read(&vslow_work_executing_count) < vsmax);
707}
708
709/*
710 * Worker thread dispatcher
711 */
712static int slow_work_thread(void *_data)
713{
714 int vsmax, id;
715
716 DEFINE_WAIT(wait);
717
718 set_freezable();
719 set_user_nice(current, -5);
720
721 /* allocate ourselves an ID */
722 spin_lock_irq(&slow_work_queue_lock);
723 id = find_first_zero_bit(slow_work_ids, SLOW_WORK_THREAD_LIMIT);
724 BUG_ON(id < 0 || id >= SLOW_WORK_THREAD_LIMIT);
725 __set_bit(id, slow_work_ids);
726 slow_work_set_thread_pid(id, current->pid);
727 spin_unlock_irq(&slow_work_queue_lock);
728
729 sprintf(current->comm, "kslowd%03u", id);
730
731 for (;;) {
732 vsmax = vslow_work_proportion;
733 vsmax *= atomic_read(&slow_work_thread_count);
734 vsmax /= 100;
735
736 prepare_to_wait_exclusive(&slow_work_thread_wq, &wait,
737 TASK_INTERRUPTIBLE);
738 if (!freezing(current) &&
739 !slow_work_threads_should_exit &&
740 !slow_work_available(vsmax) &&
741 !slow_work_cull)
742 schedule();
743 finish_wait(&slow_work_thread_wq, &wait);
744
745 try_to_freeze();
746
747 vsmax = vslow_work_proportion;
748 vsmax *= atomic_read(&slow_work_thread_count);
749 vsmax /= 100;
750
751 if (slow_work_available(vsmax) && slow_work_execute(id)) {
752 cond_resched();
753 if (list_empty(&slow_work_queue) &&
754 list_empty(&vslow_work_queue) &&
755 atomic_read(&slow_work_thread_count) >
756 slow_work_min_threads)
757 slow_work_schedule_cull();
758 continue;
759 }
760
761 if (slow_work_threads_should_exit)
762 break;
763
764 if (slow_work_cull && slow_work_cull_thread())
765 break;
766 }
767
768 spin_lock_irq(&slow_work_queue_lock);
769 slow_work_set_thread_pid(id, 0);
770 __clear_bit(id, slow_work_ids);
771 spin_unlock_irq(&slow_work_queue_lock);
772
773 if (atomic_dec_and_test(&slow_work_thread_count))
774 complete_and_exit(&slow_work_last_thread_exited, 0);
775 return 0;
776}
777
778/*
779 * Handle thread cull timer expiration
780 */
781static void slow_work_cull_timeout(unsigned long data)
782{
783 slow_work_cull = true;
784 wake_up(&slow_work_thread_wq);
785}
786
787/*
788 * Start a new slow work thread
789 */
790static void slow_work_new_thread_execute(struct slow_work *work)
791{
792 struct task_struct *p;
793
794 if (slow_work_threads_should_exit)
795 return;
796
797 if (atomic_read(&slow_work_thread_count) >= slow_work_max_threads)
798 return;
799
800 if (!mutex_trylock(&slow_work_user_lock))
801 return;
802
803 slow_work_may_not_start_new_thread = true;
804 atomic_inc(&slow_work_thread_count);
805 p = kthread_run(slow_work_thread, NULL, "kslowd");
806 if (IS_ERR(p)) {
807 printk(KERN_DEBUG "Slow work thread pool: OOM\n");
808 if (atomic_dec_and_test(&slow_work_thread_count))
809 BUG(); /* we're running on a slow work thread... */
810 mod_timer(&slow_work_oom_timer,
811 round_jiffies(jiffies + SLOW_WORK_OOM_TIMEOUT));
812 } else {
813 /* ratelimit the starting of new threads */
814 mod_timer(&slow_work_oom_timer, jiffies + 1);
815 }
816
817 mutex_unlock(&slow_work_user_lock);
818}
819
820static const struct slow_work_ops slow_work_new_thread_ops = {
821 .owner = THIS_MODULE,
822 .execute = slow_work_new_thread_execute,
823#ifdef CONFIG_SLOW_WORK_DEBUG
824 .desc = slow_work_new_thread_desc,
825#endif
826};
827
828/*
829 * post-OOM new thread start suppression expiration
830 */
831static void slow_work_oom_timeout(unsigned long data)
832{
833 slow_work_may_not_start_new_thread = false;
834}
835
836#ifdef CONFIG_SYSCTL
837/*
838 * Handle adjustment of the minimum number of threads
839 */
840static int slow_work_min_threads_sysctl(struct ctl_table *table, int write,
841 void __user *buffer,
842 size_t *lenp, loff_t *ppos)
843{
844 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
845 int n;
846
847 if (ret == 0) {
848 mutex_lock(&slow_work_user_lock);
849 if (slow_work_user_count > 0) {
850 /* see if we need to start or stop threads */
851 n = atomic_read(&slow_work_thread_count) -
852 slow_work_min_threads;
853
854 if (n < 0 && !slow_work_may_not_start_new_thread)
855 slow_work_enqueue(&slow_work_new_thread);
856 else if (n > 0)
857 slow_work_schedule_cull();
858 }
859 mutex_unlock(&slow_work_user_lock);
860 }
861
862 return ret;
863}
864
865/*
866 * Handle adjustment of the maximum number of threads
867 */
868static int slow_work_max_threads_sysctl(struct ctl_table *table, int write,
869 void __user *buffer,
870 size_t *lenp, loff_t *ppos)
871{
872 int ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
873 int n;
874
875 if (ret == 0) {
876 mutex_lock(&slow_work_user_lock);
877 if (slow_work_user_count > 0) {
878 /* see if we need to stop threads */
879 n = slow_work_max_threads -
880 atomic_read(&slow_work_thread_count);
881
882 if (n < 0)
883 slow_work_schedule_cull();
884 }
885 mutex_unlock(&slow_work_user_lock);
886 }
887
888 return ret;
889}
890#endif /* CONFIG_SYSCTL */
891
892/**
893 * slow_work_register_user - Register a user of the facility
894 * @module: The module about to make use of the facility
895 *
896 * Register a user of the facility, starting up the initial threads if there
897 * aren't any other users at this point. This will return 0 if successful, or
898 * an error if not.
899 */
900int slow_work_register_user(struct module *module)
901{
902 struct task_struct *p;
903 int loop;
904
905 mutex_lock(&slow_work_user_lock);
906
907 if (slow_work_user_count == 0) {
908 printk(KERN_NOTICE "Slow work thread pool: Starting up\n");
909 init_completion(&slow_work_last_thread_exited);
910
911 slow_work_threads_should_exit = false;
912 slow_work_init(&slow_work_new_thread,
913 &slow_work_new_thread_ops);
914 slow_work_may_not_start_new_thread = false;
915 slow_work_cull = false;
916
917 /* start the minimum number of threads */
918 for (loop = 0; loop < slow_work_min_threads; loop++) {
919 atomic_inc(&slow_work_thread_count);
920 p = kthread_run(slow_work_thread, NULL, "kslowd");
921 if (IS_ERR(p))
922 goto error;
923 }
924 printk(KERN_NOTICE "Slow work thread pool: Ready\n");
925 }
926
927 slow_work_user_count++;
928 mutex_unlock(&slow_work_user_lock);
929 return 0;
930
931error:
932 if (atomic_dec_and_test(&slow_work_thread_count))
933 complete(&slow_work_last_thread_exited);
934 if (loop > 0) {
935 printk(KERN_ERR "Slow work thread pool:"
936 " Aborting startup on ENOMEM\n");
937 slow_work_threads_should_exit = true;
938 wake_up_all(&slow_work_thread_wq);
939 wait_for_completion(&slow_work_last_thread_exited);
940 printk(KERN_ERR "Slow work thread pool: Aborted\n");
941 }
942 mutex_unlock(&slow_work_user_lock);
943 return PTR_ERR(p);
944}
945EXPORT_SYMBOL(slow_work_register_user);
946
947/*
948 * wait for all outstanding items from the calling module to complete
949 * - note that more items may be queued whilst we're waiting
950 */
951static void slow_work_wait_for_items(struct module *module)
952{
953#ifdef CONFIG_MODULES
954 DECLARE_WAITQUEUE(myself, current);
955 struct slow_work *work;
956 int loop;
957
958 mutex_lock(&slow_work_unreg_sync_lock);
959 add_wait_queue(&slow_work_unreg_wq, &myself);
960
961 for (;;) {
962 spin_lock_irq(&slow_work_queue_lock);
963
964 /* first of all, we wait for the last queued item in each list
965 * to be processed */
966 list_for_each_entry_reverse(work, &vslow_work_queue, link) {
967 if (work->owner == module) {
968 set_current_state(TASK_UNINTERRUPTIBLE);
969 slow_work_unreg_work_item = work;
970 goto do_wait;
971 }
972 }
973 list_for_each_entry_reverse(work, &slow_work_queue, link) {
974 if (work->owner == module) {
975 set_current_state(TASK_UNINTERRUPTIBLE);
976 slow_work_unreg_work_item = work;
977 goto do_wait;
978 }
979 }
980
981 /* then we wait for the items being processed to finish */
982 slow_work_unreg_module = module;
983 smp_mb();
984 for (loop = 0; loop < SLOW_WORK_THREAD_LIMIT; loop++) {
985 if (slow_work_thread_processing[loop] == module)
986 goto do_wait;
987 }
988 spin_unlock_irq(&slow_work_queue_lock);
989 break; /* okay, we're done */
990
991 do_wait:
992 spin_unlock_irq(&slow_work_queue_lock);
993 schedule();
994 slow_work_unreg_work_item = NULL;
995 slow_work_unreg_module = NULL;
996 }
997
998 remove_wait_queue(&slow_work_unreg_wq, &myself);
999 mutex_unlock(&slow_work_unreg_sync_lock);
1000#endif /* CONFIG_MODULES */
1001}
1002
1003/**
1004 * slow_work_unregister_user - Unregister a user of the facility
1005 * @module: The module whose items should be cleared
1006 *
1007 * Unregister a user of the facility, killing all the threads if this was the
1008 * last one.
1009 *
1010 * This waits for all the work items belonging to the nominated module to go
1011 * away before proceeding.
1012 */
1013void slow_work_unregister_user(struct module *module)
1014{
1015 /* first of all, wait for all outstanding items from the calling module
1016 * to complete */
1017 if (module)
1018 slow_work_wait_for_items(module);
1019
1020 /* then we can actually go about shutting down the facility if need
1021 * be */
1022 mutex_lock(&slow_work_user_lock);
1023
1024 BUG_ON(slow_work_user_count <= 0);
1025
1026 slow_work_user_count--;
1027 if (slow_work_user_count == 0) {
1028 printk(KERN_NOTICE "Slow work thread pool: Shutting down\n");
1029 slow_work_threads_should_exit = true;
1030 del_timer_sync(&slow_work_cull_timer);
1031 del_timer_sync(&slow_work_oom_timer);
1032 wake_up_all(&slow_work_thread_wq);
1033 wait_for_completion(&slow_work_last_thread_exited);
1034 printk(KERN_NOTICE "Slow work thread pool:"
1035 " Shut down complete\n");
1036 }
1037
1038 mutex_unlock(&slow_work_user_lock);
1039}
1040EXPORT_SYMBOL(slow_work_unregister_user);
1041
1042/*
1043 * Initialise the slow work facility
1044 */
1045static int __init init_slow_work(void)
1046{
1047 unsigned nr_cpus = num_possible_cpus();
1048
1049 if (slow_work_max_threads < nr_cpus)
1050 slow_work_max_threads = nr_cpus;
1051#ifdef CONFIG_SYSCTL
1052 if (slow_work_max_max_threads < nr_cpus * 2)
1053 slow_work_max_max_threads = nr_cpus * 2;
1054#endif
1055#ifdef CONFIG_SLOW_WORK_DEBUG
1056 {
1057 struct dentry *dbdir;
1058
1059 dbdir = debugfs_create_dir("slow_work", NULL);
1060 if (dbdir && !IS_ERR(dbdir))
1061 debugfs_create_file("runqueue", S_IFREG | 0400, dbdir,
1062 NULL, &slow_work_runqueue_fops);
1063 }
1064#endif
1065 return 0;
1066}
1067
1068subsys_initcall(init_slow_work);
diff --git a/kernel/slow-work.h b/kernel/slow-work.h
deleted file mode 100644
index a29ebd1ef41d..000000000000
--- a/kernel/slow-work.h
+++ /dev/null
@@ -1,72 +0,0 @@
1/* Slow work private definitions
2 *
3 * Copyright (C) 2009 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#define SLOW_WORK_CULL_TIMEOUT (5 * HZ) /* cull threads 5s after running out of
13 * things to do */
14#define SLOW_WORK_OOM_TIMEOUT (5 * HZ) /* can't start new threads for 5s after
15 * OOM */
16
17#define SLOW_WORK_THREAD_LIMIT 255 /* abs maximum number of slow-work threads */
18
19/*
20 * slow-work.c
21 */
22#ifdef CONFIG_SLOW_WORK_DEBUG
23extern struct slow_work *slow_work_execs[];
24extern pid_t slow_work_pids[];
25extern rwlock_t slow_work_execs_lock;
26#endif
27
28extern struct list_head slow_work_queue;
29extern struct list_head vslow_work_queue;
30extern spinlock_t slow_work_queue_lock;
31
32/*
33 * slow-work-debugfs.c
34 */
35#ifdef CONFIG_SLOW_WORK_DEBUG
36extern const struct file_operations slow_work_runqueue_fops;
37
38extern void slow_work_new_thread_desc(struct slow_work *, struct seq_file *);
39#endif
40
41/*
42 * Helper functions
43 */
44static inline void slow_work_set_thread_pid(int id, pid_t pid)
45{
46#ifdef CONFIG_SLOW_WORK_DEBUG
47 slow_work_pids[id] = pid;
48#endif
49}
50
51static inline void slow_work_mark_time(struct slow_work *work)
52{
53#ifdef CONFIG_SLOW_WORK_DEBUG
54 work->mark = CURRENT_TIME;
55#endif
56}
57
58static inline void slow_work_begin_exec(int id, struct slow_work *work)
59{
60#ifdef CONFIG_SLOW_WORK_DEBUG
61 slow_work_execs[id] = work;
62#endif
63}
64
65static inline void slow_work_end_exec(int id, struct slow_work *work)
66{
67#ifdef CONFIG_SLOW_WORK_DEBUG
68 write_lock(&slow_work_execs_lock);
69 slow_work_execs[id] = NULL;
70 write_unlock(&slow_work_execs_lock);
71#endif
72}
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index d24f761f4876..5821365b9605 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -50,7 +50,6 @@
50#include <linux/acpi.h> 50#include <linux/acpi.h>
51#include <linux/reboot.h> 51#include <linux/reboot.h>
52#include <linux/ftrace.h> 52#include <linux/ftrace.h>
53#include <linux/slow-work.h>
54#include <linux/perf_event.h> 53#include <linux/perf_event.h>
55#include <linux/kprobes.h> 54#include <linux/kprobes.h>
56#include <linux/pipe_fs_i.h> 55#include <linux/pipe_fs_i.h>
@@ -906,13 +905,6 @@ static struct ctl_table kern_table[] = {
906 .proc_handler = proc_dointvec, 905 .proc_handler = proc_dointvec,
907 }, 906 },
908#endif 907#endif
909#ifdef CONFIG_SLOW_WORK
910 {
911 .procname = "slow-work",
912 .mode = 0555,
913 .child = slow_work_sysctls,
914 },
915#endif
916#ifdef CONFIG_PERF_EVENTS 908#ifdef CONFIG_PERF_EVENTS
917 { 909 {
918 .procname = "perf_event_paranoid", 910 .procname = "perf_event_paranoid",
generated by cgit v1.2.2 (git 2.25.0) at 2025-11-27 14:38:18 -0500