Impact: better handling of CPU buffer start annotation

Because of the confusion with the per CPU buffers wrapping where
one CPU might be more active at the end of the trace than the other
CPUs causing that one CPU to have a shorter history. Kernel
developers were confused by the "missing" data of that one CPU
at the beginning of the trace output. An annotation was added to
the trace output to show that the buffer had started:

 # tracer: function
 #
 #           TASK-PID    CPU#    TIMESTAMP  FUNCTION
 #              | |       |          |         |
 ##### CPU 3 buffer started ####
          <idle>-0     [003]   158.192959: smp_apic_timer_interrupt
 [...]
           <idle>-0     [003]   161.556520: default_idle
 ##### CPU 1 buffer started ####
           <idle>-0     [001]   161.592494: hrtimer_force_reprogram
 [etc]

But this annotation gets a bit messy when tracers do not fill the
buffers. This patch does a couple of things:

 One) it adds a flag to trace_options to disable these annotations

 Two) it does not annotate if the tracer did not overflow its buffer.

This makes the output much cleaner.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: rename file /debug/tracing/iter_ctrl to /debug/tracing/trace_options

The original ftrace had a file called "iter_ctrl" that would control
the way the output was iterated. But this file grew into a catch all
for different trace options. This patch renames the file from iter_ctrl
to trace_options to reflect this change.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: change the units of buffer_size_kb to kilobytes

This patch changes the units of the buffer_size_kb file to kilobytes.
Reading and writing to the file uses kilobytes as units. To help
users to know what units are used, the output of the file now
looks like:

  # cat /debug/tracing/buffer_size_kb
  1408
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: rename of debugfs file trace_entries to buffer_size_kb

The original ftrace had fixed size entries, and the number of entries
was shown and modified via the file called trace_entries. By converting
to the unified trace buffer, we now allow for variable size entries
which makes the meaning of trace_entries pointless.

Since trace_size might be confused to the size of the trace, this patch
names it "buffer_size_kb" (thanks to Arjan van de Ven for this idea).

[ mingo@elte.hu: changed from buffer_size to buffer_size_kb ]

( Note, the units are still bytes - the next patch changes that,
  to keep the wide rename patch separate from the unit-change patch. )
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Merge branches 'tracing/branch-tracer', 'tracing/fastboot', 'tracing/function-return-tracer' and 'tracing/urgent' into tracing/core

Impact: Optimize a bit the function return tracer

This patch changes the calling convention of prepare_ftrace_return to
pass its arguments by register. This will optimize it a bit and
prepare it to support dynamic tracing.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: remove spinlocks and irq disabling in function return tracer.

I've tried to figure out all of the race condition that could happen
when the tracer pushes or pops a return address trace to/from the
current thread_info.

Theory:

_ One thread can only execute on one cpu at a time. So this code
  doesn't need to be SMP-safe. Just drop the spinlock.

_ The only race could happen between the current thread and an
  interrupt. If an interrupt is raised, it will increase the index of
  the return stack storage and then execute until the end of the
  tracing to finally free the index it used. We don't need to disable
  irqs.

This is theorical. In practice, I've tested it with a two-core SMP and
had no problem at all. Perhaps -tip testing could confirm it.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: File name change of trace_unlikely.c

The "unlikely" name for the tracer is quite ugly. We renamed all the
parts of it to "branch" and now it is time to rename the file too.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: added new branch tracer

Currently the tracing of branch profiling (unlikelys and likelys hit)
is only activated by the iter_ctrl. This patch adds a tracer called
"branch" that will just trace the branch profiling. The advantage
of adding this tracer is that it can be added to the ftrace selftests
on startup.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: rename of iter_ctrl unlikely to branch

The unlikely name is ugly. This patch converts the iter_ctrl command
"unlikely" and "nounlikely" to "branch" and "nobranch" respectively.

It also renames a lot of internal functions to use "branch" instead
of "unlikely".
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: name change of unlikely tracer and profiler

Ingo Molnar suggested changing the config from UNLIKELY_PROFILE
to BRANCH_PROFILING. I never did like the "unlikely" name so I
went one step farther, and renamed all the unlikely configurations
to a "BRANCH" variant.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: cleanup

Fix the following warning from the perl syntax checking tool perlcritic.
This tool is a lint like tool that checks for perl best practices.

Loop iterator is not lexical at line 113, column 1.
See page 108 of PBP.  (Severity: 5)
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Steve suggested the to change the output from this:

>  bash-3471  [003]   357.014755: [ MISS ] sched_info_dequeued:sched_stats.h:177
>  bash-3471  [003]   357.014756: [ .... ] update_curr:sched_fair.c:489
>  bash-3471  [003]   357.014758: [ .... ] calc_delta_fair:sched_fair.c:411

to this:

>  bash-3471  [003]   357.014755: [ MISS ] sched_info_dequeued:sched_stats.h:177
>  bash-3471  [003]   357.014756: [  ok  ] update_curr:sched_fair.c:489
>  bash-3471  [003]   357.014758: [  ok  ] calc_delta_fair:sched_fair.c:411

as it makes it clearer to the user what it means exactly.
Acked-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix bootup crash

the branch tracer missed arch/x86/vdso/vclock_gettime.c from
disabling tracing, which caused such bootup crashes:

  [  201.840097] init[1]: segfault at 7fffed3fe7c0 ip 00007fffed3fea2e sp 000077

also clean up the ugly ifdefs in arch/x86/kernel/vsyscall_64.c by
creating DISABLE_UNLIKELY_PROFILE facility for code to turn off
instrumentation on a per file basis.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: modify the tracer output, to make it a bit easier to read

Change the output from:

>  bash-3471  [003]   357.014755: [INCORRECT] sched_info_dequeued:sched_stats.h:177
>  bash-3471  [003]   357.014756: [correct] update_curr:sched_fair.c:489
>  bash-3471  [003]   357.014758: [correct] calc_delta_fair:sched_fair.c:411

to:

>  bash-3471  [003]   357.014755: [ MISS ] sched_info_dequeued:sched_stats.h:177
>  bash-3471  [003]   357.014756: [ .... ] update_curr:sched_fair.c:489
>  bash-3471  [003]   357.014758: [ .... ] calc_delta_fair:sched_fair.c:411

it's good to have fields aligned vertically, and the only important
information is a prediction miss, so display only that information.
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new likely/unlikely branch tracer

This patch adds a way to record the instances of the likely() and unlikely()
branch condition annotations.

When "unlikely" is set in /debugfs/tracing/iter_ctrl the unlikely conditions
will be added to any of the ftrace tracers. The change takes effect when
a new tracer is passed into the current_tracer file.

For example:

 bash-3471  [003]   357.014755: [INCORRECT] sched_info_dequeued:sched_stats.h:177
 bash-3471  [003]   357.014756: [correct] update_curr:sched_fair.c:489
 bash-3471  [003]   357.014758: [correct] calc_delta_fair:sched_fair.c:411
 bash-3471  [003]   357.014759: [correct] account_group_exec_runtime:sched_stats.h:356
 bash-3471  [003]   357.014761: [correct] update_curr:sched_fair.c:489
 bash-3471  [003]   357.014763: [INCORRECT] calc_delta_fair:sched_fair.c:411
 bash-3471  [003]   357.014765: [correct] calc_delta_mine:sched.c:1279

Which shows the normal tracer heading, as well as whether the condition was
correct "[correct]" or was mistaken "[INCORRECT]", followed by the function,
file name and line number.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: new unlikely/likely profiler

Andrew Morton recently suggested having an in-kernel way to profile
likely and unlikely macros. This patch achieves that goal.

When configured, every(*) likely and unlikely macro gets a counter attached
to it. When the condition is hit, the hit and misses of that condition
are recorded. These numbers can later be retrieved by:

  /debugfs/tracing/profile_likely    - All likely markers
  /debugfs/tracing/profile_unlikely  - All unlikely markers.

# cat /debug/tracing/profile_unlikely | head
 correct incorrect  %        Function                  File              Line
 ------- ---------  -        --------                  ----              ----
    2167        0   0 do_arch_prctl                  process_64.c         832
       0        0   0 do_arch_prctl                  process_64.c         804
    2670        0   0 IS_ERR                         err.h                34
   71230     5693   7 __switch_to                    process_64.c         673
   76919        0   0 __switch_to                    process_64.c         639
   43184    33743  43 __switch_to                    process_64.c         624
   12740    64181  83 __switch_to                    process_64.c         594
   12740    64174  83 __switch_to                    process_64.c         590

# cat /debug/tracing/profile_unlikely | \
  awk '{ if ($3 > 25) print $0; }' |head -20
   44963    35259  43 __switch_to                    process_64.c         624
   12762    67454  84 __switch_to                    process_64.c         594
   12762    67447  84 __switch_to                    process_64.c         590
    1478      595  28 syscall_get_error              syscall.h            51
       0     2821 100 syscall_trace_leave            ptrace.c             1567
       0        1 100 native_smp_prepare_cpus        smpboot.c            1237
   86338   265881  75 calc_delta_fair                sched_fair.c         408
  210410   108540  34 calc_delta_mine                sched.c              1267
       0    54550 100 sched_info_queued              sched_stats.h        222
   51899    66435  56 pick_next_task_fair            sched_fair.c         1422
       6       10  62 yield_task_fair                sched_fair.c         982
    7325     2692  26 rt_policy                      sched.c              144
       0     1270 100 pre_schedule_rt                sched_rt.c           1261
    1268    48073  97 pick_next_task_rt              sched_rt.c           884
       0    45181 100 sched_info_dequeued            sched_stats.h        177
       0       15 100 sched_move_task                sched.c              8700
       0       15 100 sched_move_task                sched.c              8690
   53167    33217  38 schedule                       sched.c              4457
       0    80208 100 sched_info_switch              sched_stats.h        270
   30585    49631  61 context_switch                 sched.c              2619

# cat /debug/tracing/profile_likely | awk '{ if ($3 > 25) print $0; }'
   39900    36577  47 pick_next_task                 sched.c              4397
   20824    15233  42 switch_mm                      mmu_context_64.h     18
       0        7 100 __cancel_work_timer            workqueue.c          560
     617    66484  99 clocksource_adjust             timekeeping.c        456
       0   346340 100 audit_syscall_exit             auditsc.c            1570
      38   347350  99 audit_get_context              auditsc.c            732
       0   345244 100 audit_syscall_entry            auditsc.c            1541
      38     1017  96 audit_free                     auditsc.c            1446
       0     1090 100 audit_alloc                    auditsc.c            862
    2618     1090  29 audit_alloc                    auditsc.c            858
       0        6 100 move_masked_irq                migration.c          9
       1      198  99 probe_sched_wakeup             trace_sched_switch.c 58
       2        2  50 probe_wakeup                   trace_sched_wakeup.c 227
       0        2 100 probe_wakeup_sched_switch      trace_sched_wakeup.c 144
    4514     2090  31 __grab_cache_page              filemap.c            2149
   12882   228786  94 mapping_unevictable            pagemap.h            50
       4       11  73 __flush_cpu_slab               slub.c               1466
  627757   330451  34 slab_free                      slub.c               1731
    2959    61245  95 dentry_lru_del_init            dcache.c             153
     946     1217  56 load_elf_binary                binfmt_elf.c         904
     102       82  44 disk_put_part                  genhd.h              206
       1        1  50 dst_gc_task                    dst.c                82
       0       19 100 tcp_mss_split_point            tcp_output.c         1126

As you can see by the above, there's a bit of work to do in rethinking
the use of some unlikelys and likelys. Note: the unlikely case had 71 hits
that were more than 25%.

Note:  After submitting my first version of this patch, Andrew Morton
  showed me a version written by Daniel Walker, where I picked up
  the following ideas from:

  1)  Using __builtin_constant_p to avoid profiling fixed values.
  2)  Using __FILE__ instead of instruction pointers.
  3)  Using the preprocessor to stop all profiling of likely
       annotations from vsyscall_64.c.

Thanks to Andrew Morton, Arjan van de Ven, Theodore Tso and Ingo Molnar
for their feed back on this patch.

(*) Not ever unlikely is recorded, those that are used by vsyscalls
 (a few of them) had to have profiling disabled.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Theodore Tso <tytso@mit.edu>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Merge branches 'tracing/fastboot', 'tracing/function-return-tracer' and 'tracing/ring-buffer' into tracing/core

Impact: deadlock fix in ring_buffer_read_start

The ring_buffer_iter_reset was called from ring_buffer_read_start
where both grabbed the reader_lock.

This patch separates out the internals of ring_buffer_iter_reset
to its own function so that both APIs may grab the reader_lock.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: disable preemption when calling sched_clock()

The ring_buffer_time_stamp still uses sched_clock as its counter.
But it is a bug to call it with preemption enabled. This requirement
should not be pushed to the ring_buffer_time_stamp callers, so
the ring_buffer_time_stamp needs to disable preemption when calling
sched_clock.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: Split the boot tracer entries in two parts: call and return

Now that we are using the sched tracer from the boot tracer, we want
to use the same timestamp than the ring-buffer to have consistent time
captures between sched events and initcall events.

So we get rid of the old time capture by the boot tracer and split the
initcall events in two parts: call and return. This way we have the
ring buffer timestamp of both.

An example trace:

[   27.904149584] calling  net_ns_init+0x0/0x1c0 @ 1
[   27.904429624] initcall net_ns_init+0x0/0x1c0 returned 0 after 0 msecs
[   27.904575926] calling  reboot_init+0x0/0x20 @ 1
[   27.904655399] initcall reboot_init+0x0/0x20 returned 0 after 0 msecs
[   27.904800228] calling  sysctl_init+0x0/0x30 @ 1
[   27.905142914] initcall sysctl_init+0x0/0x30 returned 0 after 0 msecs
[   27.905287211] calling  ksysfs_init+0x0/0xb0 @ 1
 ##### CPU 0 buffer started ####
            init-1     [000]    27.905395:      1:120:R   + [001]    11:115:S
 ##### CPU 1 buffer started ####
          <idle>-0     [001]    27.905425:      0:140:R ==> [001]    11:115:R
            init-1     [000]    27.905426:      1:120:D ==> [000]     0:140:R
          <idle>-0     [000]    27.905431:      0:140:R   + [000]     4:115:S
          <idle>-0     [000]    27.905451:      0:140:R ==> [000]     4:115:R
     ksoftirqd/0-4     [000]    27.905456:      4:115:S ==> [000]     0:140:R
           udevd-11    [001]    27.905458:     11:115:R   + [001]    14:115:R
          <idle>-0     [000]    27.905459:      0:140:R   + [000]     4:115:S
          <idle>-0     [000]    27.905462:      0:140:R ==> [000]     4:115:R
           udevd-11    [001]    27.905462:     11:115:R ==> [001]    14:115:R
     ksoftirqd/0-4     [000]    27.905467:      4:115:S ==> [000]     0:140:R
          <idle>-0     [000]    27.905470:      0:140:R   + [000]     4:115:S
          <idle>-0     [000]    27.905473:      0:140:R ==> [000]     4:115:R
     ksoftirqd/0-4     [000]    27.905476:      4:115:S ==> [000]     0:140:R
          <idle>-0     [000]    27.905479:      0:140:R   + [000]     4:115:S
          <idle>-0     [000]    27.905482:      0:140:R ==> [000]     4:115:R
     ksoftirqd/0-4     [000]    27.905486:      4:115:S ==> [000]     0:140:R
           udevd-14    [001]    27.905499:     14:120:X ==> [001]    11:115:R
           udevd-11    [001]    27.905506:     11:115:R   + [000]     1:120:D
          <idle>-0     [000]    27.905515:      0:140:R ==> [000]     1:120:R
           udevd-11    [001]    27.905517:     11:115:S ==> [001]     0:140:R
[   27.905557107] initcall ksysfs_init+0x0/0xb0 returned 0 after 3906 msecs
[   27.905705736] calling  init_jiffies_clocksource+0x0/0x10 @ 1
[   27.905779239] initcall init_jiffies_clocksource+0x0/0x10 returned 0 after 0 msecs
[   27.906769814] calling  pm_init+0x0/0x30 @ 1
[   27.906853627] initcall pm_init+0x0/0x30 returned 0 after 0 msecs
[   27.906997803] calling  pm_disk_init+0x0/0x20 @ 1
[   27.907076946] initcall pm_disk_init+0x0/0x20 returned 0 after 0 msecs
[   27.907222556] calling  swsusp_header_init+0x0/0x30 @ 1
[   27.907294325] initcall swsusp_header_init+0x0/0x30 returned 0 after 0 msecs
[   27.907439620] calling  stop_machine_init+0x0/0x50 @ 1
            init-1     [000]    27.907485:      1:120:R   + [000]     2:115:S
            init-1     [000]    27.907490:      1:120:D ==> [000]     2:115:R
        kthreadd-2     [000]    27.907507:      2:115:R   + [001]    15:115:R
          <idle>-0     [001]    27.907517:      0:140:R ==> [001]    15:115:R
        kthreadd-2     [000]    27.907517:      2:115:D ==> [000]     0:140:R
          <idle>-0     [000]    27.907521:      0:140:R   + [000]     4:115:S
          <idle>-0     [000]    27.907524:      0:140:R ==> [000]     4:115:R
           udevd-15    [001]    27.907527:     15:115:D   + [000]     2:115:D
     ksoftirqd/0-4     [000]    27.907537:      4:115:S ==> [000]     2:115:R
           udevd-15    [001]    27.907537:     15:115:D ==> [001]     0:140:R
        kthreadd-2     [000]    27.907546:      2:115:R   + [000]     1:120:D
        kthreadd-2     [000]    27.907550:      2:115:S ==> [000]     1:120:R
            init-1     [000]    27.907584:      1:120:R   + [000]    15:  0:D
            init-1     [000]    27.907589:      1:120:R   + [000]     2:115:S
            init-1     [000]    27.907593:      1:120:D ==> [000]    15:  0:R
           udevd-15    [000]    27.907601:     15:  0:S ==> [000]     2:115:R
 ##### CPU 0 buffer started ####
        kthreadd-2     [000]    27.907616:      2:115:R   + [001]    16:115:R
 ##### CPU 1 buffer started ####
          <idle>-0     [001]    27.907620:      0:140:R ==> [001]    16:115:R
        kthreadd-2     [000]    27.907621:      2:115:D ==> [000]     0:140:R
           udevd-16    [001]    27.907625:     16:115:D   + [000]     2:115:D
          <idle>-0     [000]    27.907628:      0:140:R   + [000]     4:115:S
           udevd-16    [001]    27.907629:     16:115:D ==> [001]     0:140:R
          <idle>-0     [000]    27.907631:      0:140:R ==> [000]     4:115:R
     ksoftirqd/0-4     [000]    27.907636:      4:115:S ==> [000]     2:115:R
        kthreadd-2     [000]    27.907644:      2:115:R   + [000]     1:120:D
        kthreadd-2     [000]    27.907647:      2:115:S ==> [000]     1:120:R
            init-1     [000]    27.907657:      1:120:R   + [001]    16:  0:D
          <idle>-0     [001]    27.907666:      0:140:R ==> [001]    16:  0:R
[   27.907703862] initcall stop_machine_init+0x0/0x50 returned 0 after 0 msecs
[   27.907850704] calling  filelock_init+0x0/0x30 @ 1
[   27.907926573] initcall filelock_init+0x0/0x30 returned 0 after 0 msecs
[   27.908071327] calling  init_script_binfmt+0x0/0x10 @ 1
[   27.908165195] initcall init_script_binfmt+0x0/0x10 returned 0 after 0 msecs
[   27.908309461] calling  init_elf_binfmt+0x0/0x10 @ 1
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: Cleanups on the boot tracer and ftrace

This patch bring some cleanups about the boot tracer headers. The
functions and structures of this tracer have nothing related to ftrace
and should have so their own header file.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: NSteven Rostedt <rostedt@goodmis.org>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Conflicts:
	kernel/trace/ring_buffer.c

Impact: Restructure WARN_ONs in ring_buffer.c

The current WARN_ON macros in ring_buffer.c are quite ugly.

This patch cleans them up and uses a single RB_WARN_ON that returns
the value of the condition. This allows the caller to abort the
function if the condition is true.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Merge branch 'devel' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace into tracing/urgent

Impact: enable/disable ring buffer recording API added

Several kernel developers have requested that there be a way to stop
recording into the ring buffers with a simple switch that can also
be enabled from userspace. This patch addes a new kernel API to the
ring buffers called:

 tracing_on()
 tracing_off()

When tracing_off() is called, all ring buffers will not be able to record
into their buffers.

tracing_on() will enable the ring buffers again.

These two act like an on/off switch. That is, there is no counting of the
number of times tracing_off or tracing_on has been called.

A new file is added to the debugfs/tracing directory called

  tracing_on

This allows for userspace applications to also flip the switch.

  echo 0 > debugfs/tracing/tracing_on

disables the tracing.

  echo 1 > /debugfs/tracing/tracing_on

enables it.

Note, this does not disable or enable any tracers. It only sets or clears
a flag that needs to be set in order for the ring buffers to write to
their buffers. It is a global flag, and affects all ring buffers.

The buffers start out with tracing_on enabled.

There are now three flags that control recording into the buffers:

 tracing_on: which affects all ring buffer tracers.

 buffer->record_disabled: which affects an allocated buffer, which may be set
     if an anomaly is detected, and tracing is disabled.

 cpu_buffer->record_disabled: which is set by tracing_stop() or if an
     anomaly is detected. tracing_start can not reenable this if
     an anomaly occurred.

The userspace debugfs/tracing/tracing_enabled is implemented with
tracing_stop() but the user space code can not enable it if the kernel
called tracing_stop().

Userspace can enable the tracing_on even if the kernel disabled it.
It is just a switch used to stop tracing if a condition was hit.
tracing_on is not for protecting critical areas in the kernel nor is
it for stopping tracing if an anomaly occurred. This is because userspace
can reenable it at any time.

Side effect: With this patch, I discovered a dead variable in ftrace.c
  called tracing_on. This patch removes it.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>

Merge branch 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'timers-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  timers: handle HRTIMER_CB_IRQSAFE_UNLOCKED correctly from softirq context
  nohz: disable tick_nohz_kick_tick() for now
  irq: call __irq_enter() before calling the tick_idle_check
  x86: HPET: enter hpet_interrupt_handler with interrupts disabled
  x86: HPET: read from HPET_Tn_CMP() not HPET_T0_CMP
  x86: HPET: convert WARN_ON to WARN_ON_ONCE

Merge branch 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'sched-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  sched: release buddies on yield
  fix for account_group_exec_runtime(), make sure ->signal can't be freed under rq->lock
  sched: clean up debug info

Merge branch 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'tracing-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  ring-buffer: prevent infinite looping on time stamping
  ftrace: disable tracing on resize
  ftrace: fix breakage in bin_fmt results
  ftrace: ftrace.txt version update
  ftrace: update txt document

Impact: serialize reader accesses to individual CPU ring buffers

The code in the ring buffer expects only one reader at a time, but currently
it puts that requirement on the caller. This is not strong enough, and this
patch adds a "reader_lock" that serializes the access to the reader API
of the ring buffer.
Signed-off-by: NSteven Rostedt <srostedt@redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

* 'for-linus' of git://oss.sgi.com/xfs/xfs:
  [XFS] XFS: Check for valid transaction headers in recovery
  [XFS] handle memory allocation failures during log initialisation
  [XFS] Account for allocated blocks when expanding directories
  [XFS] Wait for all I/O on truncate to zero file size
  [XFS] Fix use-after-free with log and quotas

* 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mfasheh/ocfs2: (21 commits)
  ocfs2: Check search result in ocfs2_xattr_block_get()
  ocfs2: fix printk related build warnings in xattr.c
  ocfs2: truncate outstanding block after direct io failure
  ocfs2/xattr: Proper hash collision handle in bucket division
  ocfs2: return 0 in page_mkwrite to let VFS retry.
  ocfs2: Set journal descriptor to NULL after journal shutdown
  ocfs2: Fix check of return value of ocfs2_start_trans() in xattr.c.
  ocfs2: Let inode be really deleted when ocfs2_mknod_locked() fails
  ocfs2: Fix checking of return value of new_inode()
  ocfs2: Fix check of return value of ocfs2_start_trans()
  ocfs2: Fix some typos in xattr annotations.
  ocfs2: Remove unused ocfs2_restore_xattr_block().
  ocfs2: Don't repeat ocfs2_xattr_block_find()
  ocfs2: Specify appropriate journal access for new xattr buckets.
  ocfs2: Check errors from ocfs2_xattr_update_xattr_search()
  ocfs2: Don't return -EFAULT from a corrupt xattr entry.
  ocfs2: Check xattr block signatures properly.
  ocfs2: add handler_map array bounds checking
  ocfs2: remove duplicate definition in xattr
  ocfs2: fix function declaration and definition in xattr
  ...

Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAlan Cox <alan@redhat.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

* 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab/linux-2.6: (35 commits)
  V4L/DVB (9516): cx18: Move DVB buffer transfer handling from irq handler to work_queue
  V4L/DVB (9557): gspca: Small changes for the sensor HV7131B in zc3xx.
  V4L/DVB (9556): gspca: Bad init sequence for sensor HV7131B in zc3xx.
  V4L/DVB (9549): gspca: Fix a typo in one of gspca chips name.
  V4L/DVB (9515): cx18: Use correct Mailbox IRQ Ack values and misc IRQ handling cleanup
  V4L/DVB (9493): kconfig patch
  V4L/DVB (9527): af9015: fix compile warnings
  V4L/DVB (9524): af9013: fix bug in status reading
  V4L/DVB (9511): cx18: Mark CX18_CPU_DE_RELEASE_MDL as a slow API call
  V4L/DVB (9510): cx18: Fix write retries for registers that always change - part 2.
  V4L/DVB (9506): ivtv/cx18: fix test whether modules should be loaded or not.
  V4L/DVB (9499): cx88-mpeg: final fix for analogue only compilation + de-alloc fix
  V4L/DVB (9496): cx88-blackbird: bugfix: cx88-blackbird-mpeg-users
  V4L/DVB (9495): cx88-blackbird: bugfix: cx88-blackbird-poll-fix
  V4L/DVB (9494): anysee: initialize anysee_usb_mutex statically
  V4L/DVB (9492): unplug oops from dvb_frontend_init...
  V4L/DVB (9486): ivtv/ivtvfb: no longer experimental
  V4L/DVB (9485): ivtv: remove incorrect V4L1 & tvaudio dependency
  V4L/DVB (9482): Documentation, especially regarding audio and informational links
  V4L/DVB (9475): cx18: Disable write retries for registers that always change - part 1.
  ...

* 'merge' of git://git.kernel.org/pub/scm/linux/kernel/git/paulus/powerpc:
  powerpc: Update desktop/server defconfigs
  powerpc: Fix msr check in compat_sys_swapcontext
  powerpc: Repair device bindings documentation
  powerpc: Updated Freescale PPC related defconfigs
  powerpc: Update QE/CPM2 usb_ctlr structures for USB support
  powerpc/86xx: Correct SOC bus-frequency in GE Fanuc SBC610 DTS
  powerpc: Fix Book-E watchdog timer interval setting
  powerpc/fsl-booke: Fix synchronization bug w/local tlb invalidates

* 'drm-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/drm-2.6:
  drm/i915: Move legacy breadcrumb out of the reserved status page area
  drm/i915: Filter pci devices based on PCI_CLASS_DISPLAY_VGA
  drm/radeon: map registers at load time
  drm: Remove infrastructure for supporting i915's vblank swapping.
  i915: Remove racy delayed vblank swap ioctl.
  i915: Don't whine when pci_enable_msi() fails.
  i915: Don't attempt to short-circuit object_wait_rendering by checking domains.
  i915: Clean up sarea pointers on leavevt
  i915: Save/restore MCHBAR_RENDER_STANDBY on GM965/GM45

* 'upstream-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jgarzik/libata-dev:
  libata: fix last_reset timestamp handling
  libata: Avoid overflow in ata_tf_read_block() when tf->hba_lbal > 127
  [libata] pata_pcmcia: another memory card support
  [libata] pata_sch: notice attached slave devices
  [libata] pata_cs553*.c: cleanup kernel-doc

* git://git.kernel.org/pub/scm/linux/kernel/git/davem/sparc-2.6:
  sparc64: Update defconfig.
  Revert "sparc: correct section of current_pc()"