Merge branch 'linus' into x86/urgent

Merge reason: Merge upstream commits to avoid conflicts in upcoming patches.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

14 files changed, 360 insertions, 171 deletions

diff --git a/Documentation/RCU/whatisRCU.txt b/Documentation/RCU/whatisRCU.txt
index cfaac34c4557..6ef692667e2f 100644
--- a/Documentation/RCU/whatisRCU.txt
+++ b/Documentation/RCU/whatisRCU.txt
@@ -849,6 +849,37 @@ All:  lockdep-checked RCU-protected pointer access
 See the comment headers in the source code (or the docbook generated
 from them) for more information.
 
+However, given that there are no fewer than four families of RCU APIs
+in the Linux kernel, how do you choose which one to use?  The following
+list can be helpful:
+
+a.      Will readers need to block?  If so, you need SRCU.
+
+b.      What about the -rt patchset?  If readers would need to block
+        in an non-rt kernel, you need SRCU.  If readers would block
+        in a -rt kernel, but not in a non-rt kernel, SRCU is not
+        necessary.
+
+c.      Do you need to treat NMI handlers, hardirq handlers,
+        and code segments with preemption disabled (whether
+        via preempt_disable(), local_irq_save(), local_bh_disable(),
+        or some other mechanism) as if they were explicit RCU readers?
+        If so, you need RCU-sched.
+
+d.      Do you need RCU grace periods to complete even in the face
+        of softirq monopolization of one or more of the CPUs?  For
+        example, is your code subject to network-based denial-of-service
+        attacks?  If so, you need RCU-bh.
+
+e.      Is your workload too update-intensive for normal use of
+        RCU, but inappropriate for other synchronization mechanisms?
+        If so, consider SLAB_DESTROY_BY_RCU.  But please be careful!
+
+f.      Otherwise, use RCU.
+
+Of course, this all assumes that you have determined that RCU is in fact
+the right tool for your job.
+
 
 8.  ANSWERS TO QUICK QUIZZES
 
diff --git a/Documentation/devicetree/bindings/i2c/ce4100-i2c.txt b/Documentation/devicetree/bindings/i2c/ce4100-i2c.txt
new file mode 100644
index 000000000000..569b16248514
--- /dev/null
+++ b/Documentation/devicetree/bindings/i2c/ce4100-i2c.txt
@@ -0,0 +1,93 @@
+CE4100 I2C
+----------
+
+CE4100 has one PCI device which is described as the I2C-Controller. This
+PCI device has three PCI-bars, each bar contains a complete I2C
+controller. So we have a total of three independent I2C-Controllers
+which share only an interrupt line.
+The driver is probed via the PCI-ID and is gathering the information of
+attached devices from the devices tree.
+Grant Likely recommended to use the ranges property to map the PCI-Bar
+number to its physical address and to use this to find the child nodes
+of the specific I2C controller. This were his exact words:
+
+       Here's where the magic happens.  Each entry in
+       ranges describes how the parent pci address space
+       (middle group of 3) is translated to the local
+       address space (first group of 2) and the size of
+       each range (last cell).  In this particular case,
+       the first cell of the local address is chosen to be
+       1:1 mapped to the BARs, and the second is the
+       offset from be base of the BAR (which would be
+       non-zero if you had 2 or more devices mapped off
+       the same BAR)
+
+       ranges allows the address mapping to be described
+       in a way that the OS can interpret without
+       requiring custom device driver code.
+
+This is an example which is used on FalconFalls:
+------------------------------------------------
+        i2c-controller@b,2 {
+                #address-cells = <2>;
+                #size-cells = <1>;
+                compatible = "pci8086,2e68.2",
+                                "pci8086,2e68",
+                                "pciclass,ff0000",
+                                "pciclass,ff00";
+
+                reg = <0x15a00 0x0 0x0 0x0 0x0>;
+                interrupts = <16 1>;
+
+                /* as described by Grant, the first number in the group of
+                * three is the bar number followed by the 64bit bar address
+                * followed by size of the mapping. The bar address
+                * requires also a valid translation in parents ranges
+                * property.
+                */
+                ranges = <0 0   0x02000000 0 0xdffe0500 0x100
+                          1 0   0x02000000 0 0xdffe0600 0x100
+                          2 0   0x02000000 0 0xdffe0700 0x100>;
+
+                i2c@0 {
+                        #address-cells = <1>;
+                        #size-cells = <0>;
+                        compatible = "intel,ce4100-i2c-controller";
+
+                        /* The first number in the reg property is the
+                        * number of the bar
+                        */
+                        reg = <0 0 0x100>;
+
+                        /* This I2C controller has no devices */
+                };
+
+                i2c@1 {
+                        #address-cells = <1>;
+                        #size-cells = <0>;
+                        compatible = "intel,ce4100-i2c-controller";
+                        reg = <1 0 0x100>;
+
+                        /* This I2C controller has one gpio controller */
+                        gpio@26 {
+                                #gpio-cells = <2>;
+                                compatible = "ti,pcf8575";
+                                reg = <0x26>;
+                                gpio-controller;
+                        };
+                };
+
+                i2c@2 {
+                        #address-cells = <1>;
+                        #size-cells = <0>;
+                        compatible = "intel,ce4100-i2c-controller";
+                        reg = <2 0 0x100>;
+
+                        gpio@26 {
+                                #gpio-cells = <2>;
+                                compatible = "ti,pcf8575";
+                                reg = <0x26>;
+                                gpio-controller;
+                        };
+                };
+        };
diff --git a/Documentation/devicetree/bindings/rtc/rtc-cmos.txt b/Documentation/devicetree/bindings/rtc/rtc-cmos.txt
new file mode 100644
index 000000000000..7382989b3052
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/rtc-cmos.txt
@@ -0,0 +1,28 @@
+ Motorola mc146818 compatible RTC
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Required properties:
+  - compatible : "motorola,mc146818"
+  - reg : should contain registers location and length.
+
+Optional properties:
+  - interrupts : should contain interrupt.
+  - interrupt-parent : interrupt source phandle.
+  - ctrl-reg : Contains the initial value of the control register also
+    called "Register B".
+  - freq-reg : Contains the initial value of the frequency register also
+    called "Regsiter A".
+
+"Register A" and "B" are usually initialized by the firmware (BIOS for
+instance). If this is not done, it can be performed by the driver.
+
+ISA Example:
+
+        rtc@70 {
+                 compatible = "motorola,mc146818";
+                 interrupts = <8 3>;
+                 interrupt-parent = <&ioapic1>;
+                 ctrl-reg = <2>;
+                 freq-reg = <0x26>;
+                 reg = <1 0x70 2>;
+         };
diff --git a/Documentation/devicetree/bindings/x86/ce4100.txt b/Documentation/devicetree/bindings/x86/ce4100.txt
new file mode 100644
index 000000000000..b49ae593a60b
--- /dev/null
+++ b/Documentation/devicetree/bindings/x86/ce4100.txt
@@ -0,0 +1,38 @@
+CE4100 Device Tree Bindings
+---------------------------
+
+The CE4100 SoC uses for in core peripherals the following compatible
+format: <vendor>,<chip>-<device>.
+Many of the "generic" devices like HPET or IO APIC have the ce4100
+name in their compatible property because they first appeared in this
+SoC.
+
+The CPU node
+------------
+        cpu@0 {
+                device_type = "cpu";
+                compatible = "intel,ce4100";
+                reg = <0>;
+                lapic = <&lapic0>;
+        };
+
+The reg property describes the CPU number. The lapic property points to
+the local APIC timer.
+
+The SoC node
+------------
+
+This node describes the in-core peripherals. Required property:
+  compatible = "intel,ce4100-cp";
+
+The PCI node
+------------
+This node describes the PCI bus on the SoC. Its property should be
+  compatible = "intel,ce4100-pci", "pci";
+
+If the OS is using the IO-APIC for interrupt routing then the reported
+interrupt numbers for devices is no longer true. In order to obtain the
+correct interrupt number, the child node which represents the device has
+to contain the interrupt property. Besides the interrupt property it has
+to contain at least the reg property containing the PCI bus address and
+compatible property according to "PCI Bus Binding Revision 2.1".
diff --git a/Documentation/devicetree/bindings/x86/interrupt.txt b/Documentation/devicetree/bindings/x86/interrupt.txt
new file mode 100644
index 000000000000..7d19f494f19a
--- /dev/null
+++ b/Documentation/devicetree/bindings/x86/interrupt.txt
@@ -0,0 +1,26 @@
+Interrupt chips
+---------------
+
+* Intel I/O Advanced Programmable Interrupt Controller (IO APIC)
+
+  Required properties:
+  --------------------
+     compatible = "intel,ce4100-ioapic";
+     #interrupt-cells = <2>;
+
+  Device's interrupt property:
+
+     interrupts = <P S>;
+
+  The first number (P) represents the interrupt pin which is wired to the
+  IO APIC. The second number (S) represents the sense of interrupt which
+  should be configured and can be one of:
+    0 - Edge Rising
+    1 - Level Low
+    2 - Level High
+    3 - Edge Falling
+
+* Local APIC
+  Required property:
+
+     compatible = "intel,ce4100-lapic";
diff --git a/Documentation/devicetree/bindings/x86/timer.txt b/Documentation/devicetree/bindings/x86/timer.txt
new file mode 100644
index 000000000000..c688af58e3bd
--- /dev/null
+++ b/Documentation/devicetree/bindings/x86/timer.txt
@@ -0,0 +1,6 @@
+Timers
+------
+
+* High Precision Event Timer (HPET)
+  Required property:
+     compatible = "intel,ce4100-hpet";
diff --git a/Documentation/devicetree/booting-without-of.txt b/Documentation/devicetree/booting-without-of.txt
index 28b1c9d3d351..55fd2623445b 100644
--- a/Documentation/devicetree/booting-without-of.txt
+++ b/Documentation/devicetree/booting-without-of.txt
@@ -13,6 +13,7 @@ Table of Contents
 
   I - Introduction
     1) Entry point for arch/powerpc
+    2) Entry point for arch/x86
 
   II - The DT block format
     1) Header
@@ -225,6 +226,25 @@ it with special cases.
   cannot support both configurations with Book E and configurations
   with classic Powerpc architectures.
 
+2) Entry point for arch/x86
+-------------------------------
+
+  There is one single 32bit entry point to the kernel at code32_start,
+  the decompressor (the real mode entry point goes to the same  32bit
+  entry point once it switched into protected mode). That entry point
+  supports one calling convention which is documented in
+  Documentation/x86/boot.txt
+  The physical pointer to the device-tree block (defined in chapter II)
+  is passed via setup_data which requires at least boot protocol 2.09.
+  The type filed is defined as
+
+  #define SETUP_DTB                      2
+
+  This device-tree is used as an extension to the "boot page". As such it
+  does not parse / consider data which is already covered by the boot
+  page. This includes memory size, reserved ranges, command line arguments
+  or initrd address. It simply holds information which can not be retrieved
+  otherwise like interrupt routing or a list of devices behind an I2C bus.
 
 II - The DT block format
 ========================
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index f4a04c0c7edc..738c6fda3fb0 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2444,6 +2444,10 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         <deci-seconds>: poll all this frequency
                         0: no polling (default)
 
+        threadirqs      [KNL]
+                        Force threading of all interrupt handlers except those
+                        marked explicitely IRQF_NO_THREAD.
+
         topology=       [S390]
                         Format: {off | on}
                         Specify if the kernel should make use of the cpu
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index 631ad2f1b229..f0d3a8026a56 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -21,6 +21,7 @@ Contents:
      - SMP barrier pairing.
      - Examples of memory barrier sequences.
      - Read memory barriers vs load speculation.
+     - Transitivity
 
  (*) Explicit kernel barriers.
 
@@ -959,6 +960,63 @@ the speculation will be cancelled and the value reloaded:
         retrieved                               :       :       +-------+
 
 
+TRANSITIVITY
+------------
+
+Transitivity is a deeply intuitive notion about ordering that is not
+always provided by real computer systems.  The following example
+demonstrates transitivity (also called "cumulativity"):
+
+        CPU 1                   CPU 2                   CPU 3
+        ======================= ======================= =======================
+                { X = 0, Y = 0 }
+        STORE X=1               LOAD X                  STORE Y=1
+                                <general barrier>       <general barrier>
+                                LOAD Y                  LOAD X
+
+Suppose that CPU 2's load from X returns 1 and its load from Y returns 0.
+This indicates that CPU 2's load from X in some sense follows CPU 1's
+store to X and that CPU 2's load from Y in some sense preceded CPU 3's
+store to Y.  The question is then "Can CPU 3's load from X return 0?"
+
+Because CPU 2's load from X in some sense came after CPU 1's store, it
+is natural to expect that CPU 3's load from X must therefore return 1.
+This expectation is an example of transitivity: if a load executing on
+CPU A follows a load from the same variable executing on CPU B, then
+CPU A's load must either return the same value that CPU B's load did,
+or must return some later value.
+
+In the Linux kernel, use of general memory barriers guarantees
+transitivity.  Therefore, in the above example, if CPU 2's load from X
+returns 1 and its load from Y returns 0, then CPU 3's load from X must
+also return 1.
+
+However, transitivity is -not- guaranteed for read or write barriers.
+For example, suppose that CPU 2's general barrier in the above example
+is changed to a read barrier as shown below:
+
+        CPU 1                   CPU 2                   CPU 3
+        ======================= ======================= =======================
+                { X = 0, Y = 0 }
+        STORE X=1               LOAD X                  STORE Y=1
+                                <read barrier>          <general barrier>
+                                LOAD Y                  LOAD X
+
+This substitution destroys transitivity: in this example, it is perfectly
+legal for CPU 2's load from X to return 1, its load from Y to return 0,
+and CPU 3's load from X to return 0.
+
+The key point is that although CPU 2's read barrier orders its pair
+of loads, it does not guarantee to order CPU 1's store.  Therefore, if
+this example runs on a system where CPUs 1 and 2 share a store buffer
+or a level of cache, CPU 2 might have early access to CPU 1's writes.
+General barriers are therefore required to ensure that all CPUs agree
+on the combined order of CPU 1's and CPU 2's accesses.
+
+To reiterate, if your code requires transitivity, use general barriers
+throughout.
+
+
 ========================
 EXPLICIT KERNEL BARRIERS
 ========================
diff --git a/Documentation/rtc.txt b/Documentation/rtc.txt
index 9104c1062084..250160469d83 100644
--- a/Documentation/rtc.txt
+++ b/Documentation/rtc.txt
@@ -178,38 +178,29 @@ RTC class framework, but can't be supported by the older driver.
         setting the longer alarm time and enabling its IRQ using a single
         request (using the same model as EFI firmware).
 
-    *   RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, it probably
-        also offers update IRQs whenever the "seconds" counter changes.
-        If needed, the RTC framework can emulate this mechanism.
+    *   RTC_UIE_ON, RTC_UIE_OFF ... if the RTC offers IRQs, the RTC framework
+        will emulate this mechanism.
 
-    *   RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... another
-        feature often accessible with an IRQ line is a periodic IRQ, issued
-        at settable frequencies (usually 2^N Hz).
+    *   RTC_PIE_ON, RTC_PIE_OFF, RTC_IRQP_SET, RTC_IRQP_READ ... these icotls
+        are emulated via a kernel hrtimer.
 
 In many cases, the RTC alarm can be a system wake event, used to force
 Linux out of a low power sleep state (or hibernation) back to a fully
 operational state.  For example, a system could enter a deep power saving
 state until it's time to execute some scheduled tasks.
 
-Note that many of these ioctls need not actually be implemented by your
-driver.  The common rtc-dev interface handles many of these nicely if your
-driver returns ENOIOCTLCMD.  Some common examples:
+Note that many of these ioctls are handled by the common rtc-dev interface.
+Some common examples:
 
     *   RTC_RD_TIME, RTC_SET_TIME: the read_time/set_time functions will be
         called with appropriate values.
 
-    *   RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: the
-        set_alarm/read_alarm functions will be called.
+    *   RTC_ALM_SET, RTC_ALM_READ, RTC_WKALM_SET, RTC_WKALM_RD: gets or sets
+        the alarm rtc_timer. May call the set_alarm driver function.
 
-    *   RTC_IRQP_SET, RTC_IRQP_READ: the irq_set_freq function will be called
-        to set the frequency while the framework will handle the read for you
-        since the frequency is stored in the irq_freq member of the rtc_device
-        structure.  Your driver needs to initialize the irq_freq member during
-        init.  Make sure you check the requested frequency is in range of your
-        hardware in the irq_set_freq function.  If it isn't, return -EINVAL.  If
-        you cannot actually change the frequency, do not define irq_set_freq.
+    *   RTC_IRQP_SET, RTC_IRQP_READ: These are emulated by the generic code.
 
-    *   RTC_PIE_ON, RTC_PIE_OFF: the irq_set_state function will be called.
+    *   RTC_PIE_ON, RTC_PIE_OFF: These are also emulated by the generic code.
 
 If all else fails, check out the rtc-test.c driver!
 
diff --git a/Documentation/spinlocks.txt b/Documentation/spinlocks.txt
index 178c831b907d..2e3c64b1a6a5 100644
--- a/Documentation/spinlocks.txt
+++ b/Documentation/spinlocks.txt
@@ -86,7 +86,7 @@ to change the variables it has to get an exclusive write lock.
 
 The routines look the same as above:
 
-   rwlock_t xxx_lock = RW_LOCK_UNLOCKED;
+   rwlock_t xxx_lock = __RW_LOCK_UNLOCKED(xxx_lock);
 
         unsigned long flags;
 
@@ -196,25 +196,3 @@ appropriate:
 
 For static initialization, use DEFINE_SPINLOCK() / DEFINE_RWLOCK() or
 __SPIN_LOCK_UNLOCKED() / __RW_LOCK_UNLOCKED() as appropriate.
-
-SPIN_LOCK_UNLOCKED and RW_LOCK_UNLOCKED are deprecated.  These interfere
-with lockdep state tracking.
-
-Most of the time, you can simply turn:
-        static spinlock_t xxx_lock = SPIN_LOCK_UNLOCKED;
-into:
-        static DEFINE_SPINLOCK(xxx_lock);
-
-Static structure member variables go from:
-
-        struct foo bar {
-                .lock   =       SPIN_LOCK_UNLOCKED;
-        };
-
-to:
-
-        struct foo bar {
-                .lock   =       __SPIN_LOCK_UNLOCKED(bar.lock);
-        };
-
-Declaration of static rw_locks undergo a similar transformation.
diff --git a/Documentation/trace/ftrace-design.txt b/Documentation/trace/ftrace-design.txt
index dc52bd442c92..79fcafc7fd64 100644
--- a/Documentation/trace/ftrace-design.txt
+++ b/Documentation/trace/ftrace-design.txt
@@ -247,6 +247,13 @@ You need very few things to get the syscalls tracing in an arch.
 - Support the TIF_SYSCALL_TRACEPOINT thread flags.
 - Put the trace_sys_enter() and trace_sys_exit() tracepoints calls from ptrace
   in the ptrace syscalls tracing path.
+- If the system call table on this arch is more complicated than a simple array
+  of addresses of the system calls, implement an arch_syscall_addr to return
+  the address of a given system call.
+- If the symbol names of the system calls do not match the function names on
+  this arch, define ARCH_HAS_SYSCALL_MATCH_SYM_NAME in asm/ftrace.h and
+  implement arch_syscall_match_sym_name with the appropriate logic to return
+  true if the function name corresponds with the symbol name.
 - Tag this arch as HAVE_SYSCALL_TRACEPOINTS.
 
 
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 557c1edeccaf..1ebc24cf9a55 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -80,11 +80,11 @@ of ftrace. Here is a list of some of the key files:
         tracers listed here can be configured by
         echoing their name into current_tracer.
 
-  tracing_enabled:
+  tracing_on:
 
-        This sets or displays whether the current_tracer
-        is activated and tracing or not. Echo 0 into this
-        file to disable the tracer or 1 to enable it.
+        This sets or displays whether writing to the trace
+        ring buffer is enabled. Echo 0 into this file to disable
+        the tracer or 1 to enable it.
 
   trace:
 
@@ -202,10 +202,6 @@ Here is the list of current tracers that may be configured.
         to draw a graph of function calls similar to C code
         source.
 
-  "sched_switch"
-
-        Traces the context switches and wakeups between tasks.
-
   "irqsoff"
 
         Traces the areas that disable interrupts and saves
@@ -273,39 +269,6 @@ format, the function name that was traced "path_put" and the
 parent function that called this function "path_walk". The
 timestamp is the time at which the function was entered.
 
-The sched_switch tracer also includes tracing of task wakeups
-and context switches.
-
-     ksoftirqd/1-7     [01]  1453.070013:      7:115:R   +  2916:115:S
-     ksoftirqd/1-7     [01]  1453.070013:      7:115:R   +    10:115:S
-     ksoftirqd/1-7     [01]  1453.070013:      7:115:R ==>    10:115:R
-        events/1-10    [01]  1453.070013:     10:115:S ==>  2916:115:R
-     kondemand/1-2916  [01]  1453.070013:   2916:115:S ==>     7:115:R
-     ksoftirqd/1-7     [01]  1453.070013:      7:115:S ==>     0:140:R
-
-Wake ups are represented by a "+" and the context switches are
-shown as "==>".  The format is:
-
- Context switches:
-
-       Previous task              Next Task
-
-  <pid>:<prio>:<state>  ==>  <pid>:<prio>:<state>
-
- Wake ups:
-
-       Current task               Task waking up
-
-  <pid>:<prio>:<state>    +  <pid>:<prio>:<state>
-
-The prio is the internal kernel priority, which is the inverse
-of the priority that is usually displayed by user-space tools.
-Zero represents the highest priority (99). Prio 100 starts the
-"nice" priorities with 100 being equal to nice -20 and 139 being
-nice 19. The prio "140" is reserved for the idle task which is
-the lowest priority thread (pid 0).
-
-
 Latency trace format
 --------------------
 
@@ -491,78 +454,10 @@ x494] <- /root/a.out[+0x4a8] <- /lib/libc-2.7.so[+0x1e1a6]
                    latencies, as described in "Latency
                    trace format".
 
-sched_switch
-------------
-
-This tracer simply records schedule switches. Here is an example
-of how to use it.
-
- # echo sched_switch > current_tracer
- # echo 1 > tracing_enabled
- # sleep 1
- # echo 0 > tracing_enabled
- # cat trace
-
-# tracer: sched_switch
-#
-#           TASK-PID   CPU#    TIMESTAMP  FUNCTION
-#              | |      |          |         |
-            bash-3997  [01]   240.132281:   3997:120:R   +  4055:120:R
-            bash-3997  [01]   240.132284:   3997:120:R ==>  4055:120:R
-           sleep-4055  [01]   240.132371:   4055:120:S ==>  3997:120:R
-            bash-3997  [01]   240.132454:   3997:120:R   +  4055:120:S
-            bash-3997  [01]   240.132457:   3997:120:R ==>  4055:120:R
-           sleep-4055  [01]   240.132460:   4055:120:D ==>  3997:120:R
-            bash-3997  [01]   240.132463:   3997:120:R   +  4055:120:D
-            bash-3997  [01]   240.132465:   3997:120:R ==>  4055:120:R
-          <idle>-0     [00]   240.132589:      0:140:R   +     4:115:S
-          <idle>-0     [00]   240.132591:      0:140:R ==>     4:115:R
-     ksoftirqd/0-4     [00]   240.132595:      4:115:S ==>     0:140:R
-          <idle>-0     [00]   240.132598:      0:140:R   +     4:115:S
-          <idle>-0     [00]   240.132599:      0:140:R ==>     4:115:R
-     ksoftirqd/0-4     [00]   240.132603:      4:115:S ==>     0:140:R
-           sleep-4055  [01]   240.133058:   4055:120:S ==>  3997:120:R
- [...]
-
-
-As we have discussed previously about this format, the header
-shows the name of the trace and points to the options. The
-"FUNCTION" is a misnomer since here it represents the wake ups
-and context switches.
-
-The sched_switch file only lists the wake ups (represented with
-'+') and context switches ('==>') with the previous task or
-current task first followed by the next task or task waking up.
-The format for both of these is PID:KERNEL-PRIO:TASK-STATE.
-Remember that the KERNEL-PRIO is the inverse of the actual
-priority with zero (0) being the highest priority and the nice
-values starting at 100 (nice -20). Below is a quick chart to map
-the kernel priority to user land priorities.
-
-   Kernel Space                     User Space
- ===============================================================
-   0(high) to  98(low)     user RT priority 99(high) to 1(low)
-                           with SCHED_RR or SCHED_FIFO
- ---------------------------------------------------------------
-  99                       sched_priority is not used in scheduling
-                           decisions(it must be specified as 0)
- ---------------------------------------------------------------
- 100(high) to 139(low)     user nice -20(high) to 19(low)
- ---------------------------------------------------------------
- 140                       idle task priority
- ---------------------------------------------------------------
-
-The task states are:
-
- R - running : wants to run, may not actually be running
- S - sleep   : process is waiting to be woken up (handles signals)
- D - disk sleep (uninterruptible sleep) : process must be woken up
-                                        (ignores signals)
- T - stopped : process suspended
- t - traced  : process is being traced (with something like gdb)
- Z - zombie  : process waiting to be cleaned up
- X - unknown
-
+  overwrite - This controls what happens when the trace buffer is
+              full. If "1" (default), the oldest events are
+              discarded and overwritten. If "0", then the newest
+              events are discarded.
 
 ftrace_enabled
 --------------
@@ -607,10 +502,10 @@ an example:
  # echo irqsoff > current_tracer
  # echo latency-format > trace_options
  # echo 0 > tracing_max_latency
- # echo 1 > tracing_enabled
+ # echo 1 > tracing_on
  # ls -ltr
  [...]
- # echo 0 > tracing_enabled
+ # echo 0 > tracing_on
  # cat trace
 # tracer: irqsoff
 #
@@ -715,10 +610,10 @@ is much like the irqsoff tracer.
  # echo preemptoff > current_tracer
  # echo latency-format > trace_options
  # echo 0 > tracing_max_latency
- # echo 1 > tracing_enabled
+ # echo 1 > tracing_on
  # ls -ltr
  [...]
- # echo 0 > tracing_enabled
+ # echo 0 > tracing_on
  # cat trace
 # tracer: preemptoff
 #
@@ -863,10 +758,10 @@ tracers.
  # echo preemptirqsoff > current_tracer
  # echo latency-format > trace_options
  # echo 0 > tracing_max_latency
- # echo 1 > tracing_enabled
+ # echo 1 > tracing_on
  # ls -ltr
  [...]
- # echo 0 > tracing_enabled
+ # echo 0 > tracing_on
  # cat trace
 # tracer: preemptirqsoff
 #
@@ -1026,9 +921,9 @@ Instead of performing an 'ls', we will run 'sleep 1' under
  # echo wakeup > current_tracer
  # echo latency-format > trace_options
  # echo 0 > tracing_max_latency
- # echo 1 > tracing_enabled
+ # echo 1 > tracing_on
  # chrt -f 5 sleep 1
- # echo 0 > tracing_enabled
+ # echo 0 > tracing_on
  # cat trace
 # tracer: wakeup
 #
@@ -1140,9 +1035,9 @@ ftrace_enabled is set; otherwise this tracer is a nop.
 
  # sysctl kernel.ftrace_enabled=1
  # echo function > current_tracer
- # echo 1 > tracing_enabled
+ # echo 1 > tracing_on
  # usleep 1
- # echo 0 > tracing_enabled
+ # echo 0 > tracing_on
  # cat trace
 # tracer: function
 #
@@ -1180,7 +1075,7 @@ int trace_fd;
 [...]
 int main(int argc, char *argv[]) {
         [...]
-        trace_fd = open(tracing_file("tracing_enabled"), O_WRONLY);
+        trace_fd = open(tracing_file("tracing_on"), O_WRONLY);
         [...]
         if (condition_hit()) {
                 write(trace_fd, "0", 1);
@@ -1631,9 +1526,9 @@ If I am only interested in sys_nanosleep and hrtimer_interrupt:
  # echo sys_nanosleep hrtimer_interrupt \
                 > set_ftrace_filter
  # echo function > current_tracer
- # echo 1 > tracing_enabled
+ # echo 1 > tracing_on
  # usleep 1
- # echo 0 > tracing_enabled
+ # echo 0 > tracing_on
  # cat trace
 # tracer: ftrace
 #
@@ -1879,9 +1774,9 @@ different. The trace is live.
  # echo function > current_tracer
  # cat trace_pipe > /tmp/trace.out &
 [1] 4153
- # echo 1 > tracing_enabled
+ # echo 1 > tracing_on
  # usleep 1
- # echo 0 > tracing_enabled
+ # echo 0 > tracing_on
  # cat trace
 # tracer: function
 #
diff --git a/Documentation/trace/kprobetrace.txt b/Documentation/trace/kprobetrace.txt
index 5f77d94598dd..6d27ab8d6e9f 100644
--- a/Documentation/trace/kprobetrace.txt
+++ b/Documentation/trace/kprobetrace.txt
@@ -42,11 +42,25 @@ Synopsis of kprobe_events
   +|-offs(FETCHARG) : Fetch memory at FETCHARG +|- offs address.(**)
   NAME=FETCHARG : Set NAME as the argument name of FETCHARG.
   FETCHARG:TYPE : Set TYPE as the type of FETCHARG. Currently, basic types
-                  (u8/u16/u32/u64/s8/s16/s32/s64) and string are supported.
+                  (u8/u16/u32/u64/s8/s16/s32/s64), "string" and bitfield
+                  are supported.
 
   (*) only for return probe.
   (**) this is useful for fetching a field of data structures.
 
+Types
+-----
+Several types are supported for fetch-args. Kprobe tracer will access memory
+by given type. Prefix 's' and 'u' means those types are signed and unsigned
+respectively. Traced arguments are shown in decimal (signed) or hex (unsigned).
+String type is a special type, which fetches a "null-terminated" string from
+kernel space. This means it will fail and store NULL if the string container
+has been paged out.
+Bitfield is another special type, which takes 3 parameters, bit-width, bit-
+offset, and container-size (usually 32). The syntax is;
+
+ b<bit-width>@<bit-offset>/<container-size>
+
 
 Per-Probe Event Filtering
 -------------------------