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  1. 02 12月, 2009 4 次提交
  3. 27 11月, 2009 2 次提交
  5. 26 11月, 2009 13 次提交
    • M
      tracepoint: Add signal loss events · ba005e1f
      由 Masami Hiramatsu 提交于 
      Add signal_overflow_fail and signal_lose_info tracepoints
for signal-lost events.

Changes in v3:
 - Add docbook style comments

Changes in v2:
 - Use siginfo string macro
Suggested-by: NRoland McGrath <roland@redhat.com>
Reviewed-by: NJason Baron <jbaron@redhat.com>
Signed-off-by: NMasami Hiramatsu <mhiramat@redhat.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Oleg Nesterov <oleg@redhat.com>
LKML-Reference: <20091124215658.30449.9934.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      ba005e1f
    • M
      tracepoint: Add signal deliver event · f9d4257e
      由 Masami Hiramatsu 提交于 
      Add a tracepoint where a process gets a signal. This tracepoint
shows signal-number, sa-handler and sa-flag.

Changes in v3:
 - Add docbook style comments

Changes in v2:
 - Add siginfo argument
 - Fix comment
Signed-off-by: NMasami Hiramatsu <mhiramat@redhat.com>
Reviewed-by: NJason Baron <jbaron@redhat.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Oleg Nesterov <oleg@redhat.com>
LKML-Reference: <20091124215651.30449.20926.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      f9d4257e
    • M
      tracepoint: Move signal sending tracepoint to events/signal.h · d1eb650f
      由 Masami Hiramatsu 提交于 
      Move signal sending event to events/signal.h. This patch also
renames sched_signal_send event to signal_generate.

Changes in v4:
 - Fix a typo of task_struct pointer.

Changes in v3:
 - Add docbook style comments

Changes in v2:
 - Add siginfo argument
 - Add siginfo storing macro
Signed-off-by: NMasami Hiramatsu <mhiramat@redhat.com>
Reviewed-by: NJason Baron <jbaron@redhat.com>
Acked-by: NRoland McGrath <roland@redhat.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
Cc: Oleg Nesterov <oleg@redhat.com>
LKML-Reference: <20091124215645.30449.60208.stgit@dhcp-100-2-132.bos.redhat.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      d1eb650f
    • L
      tracing: Restore original format of sched events · 470dda74
      由 Li Zefan 提交于 
      The original format for sched_stat_iowait and sched_stat_sleep:

  $ cat events/sched/sched_stat_iowait/format
  ...
  print fmt: "comm=%s pid=%d delay=%Lu [ns]", ...
  $ cat events/sched/sched_stat_sleep/format
  ...
  print fmt: "comm=%s pid=%d delay=%Lu [ns]", ...

But commit commit 75ec29ab
("tracing: Convert some sched trace events to DEFINE_EVENT and
_PRINT") broke the format:

  $ cat events/sched/sched_stat_iowait/format
  print fmt: "task: %s:%d iowait: %Lu [ns]", ...
  $ cat events/sched/sched_stat_sleep/format
  print fmt: "task: %s:%d sleep: %Lu [ns]", ...

No change in functionality.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0E2951.9050800@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      470dda74
    • L
      tracing: Convert some ext4 events to DEFINE_TRACE · b5eb34c3
      由 Li Zefan 提交于 
      Use DECLARE_EVENT_CLASS to remove duplicate code:

   text    data     bss     dec     hex filename
 294695    6104     340  301139   49853 fs/ext4/ext4.o.old
 289983    6104     324  296411   485db fs/ext4/ext4.o

5 events are convertd:

  ext4__write_begin: ext4_write_begin, ext4_da_write_begin
  ext4__write_end: ext4_{ordered, writeback, journalled}_write_end

No change in functionality.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0E2938.2040708@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      b5eb34c3
    • L
      tracing: Convert some jbd2 events to DEFINE_EVENT · 071688f3
      由 Li Zefan 提交于 
      Use DECLARE_EVENT_CLASS to remove duplicate code:

   text    data     bss     dec     hex filename
  34903    1693     448   37044    90b4 fs/jbd2/journal.o.old
  31931    1693     416   34040    84f8 fs/jbd2/journal.o

Four events are converted:

  jbd2_commit: jbd2_start_commit,
               jbd2_commit_{locking, flushing, logging}

No change in functionality.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0E290F.7030909@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      071688f3
    • L
      tracing: Convert some block events to DEFINE_EVENT · 77ca1e02
      由 Li Zefan 提交于 
      use DECLARE_EVENT_CLASS to remove duplicate code:

   text    data     bss     dec     hex filename
  53570    3284     184   57038    dece block/blk-core.o.old
  43702    3284     144   47130    b81a block/blk-core.o

12 events are converted:

  block_rq: block_rq_insert, block_rq_issue
  block_rq_with_error: block_rq_{abort, requeue, complete}
  block_bio: block_bio_{backmerge, frontmerge, queue}
  block_get_rq: block_getrq, block_sleeprq
  block_unplug: block_unplug_timer, block_unplug_io

No change in functionality.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0E28E6.7060609@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      77ca1e02
    • L
      tracing: Convert some power events to DEFINE_EVENT · 7703466b
      由 Li Zefan 提交于 
      Use DECLARE_EVENT_CLASS to remove duplicate code:

   text    data     bss     dec     hex filename
   4312     524      12    4848    12f0 kernel/trace/power-traces.o.old
   3455     524       8    3987     f93 kernel/trace/power-traces.o

Two events are converted:

  power: power_start, power_frequency

No change in functionality.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Arjan van de Ven <arjan@infradead.org>
LKML-Reference: <4B0E28C2.1090906@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      7703466b
    • L
      tracing: Convert some workqueue events to DEFINE_EVENT · 382ece71
      由 Li Zefan 提交于 
      Use DECLARE_EVENT_CLASS to remove duplicate code:

   text    data     bss     dec     hex filename
  13171     800      72   14043    36db kernel/workqueue.o.old
  12243     800      68   13111    3337 kernel/workqueue.o

Two events are converted:

  workqueue: workqueue_insertion, workqueue_execution

No change in functionality.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0E289F.5010104@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      382ece71
    • L
      tracing: Convert softirq events to DEFINE_EVENT · c467307c
      由 Li Zefan 提交于 
      Use DECLARE_EVENT_CLASS to remove duplicate code:

   text    data     bss     dec     hex filename
  12781     952      36   13769    35c9 kernel/softirq.o.old
  11981     952      32   12965    32a5 kernel/softirq.o

Two events are converted:

  softirq: softirq_entry, softirq_exit

No change in functionality.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0E287F.4030708@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      c467307c
    • L
      tracing: Convert some kmem events to DEFINE_EVENT · 53d0422c
      由 Li Zefan 提交于 
      Use DECLARE_EVENT_CLASS to remove duplicate code:

   text    data     bss     dec     hex filename
 333987   69800   27228  431015   693a7 mm/built-in.o.old
 330030   69800   27228  427058   68432 mm/built-in.o

8 events are converted:

  kmem_alloc: kmalloc, kmem_cache_alloc
  kmem_alloc_node: kmalloc_node, kmem_cache_alloc_node
  kmem_free: kfree, kmem_cache_free
  mm_page: mm_page_alloc_zone_locked, mm_page_pcpu_drain

No change in functionality.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
LKML-Reference: <4B0E286A.2000405@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      53d0422c
    • L
      tracing: Convert module refcnt events to DEFINE_EVENT · 925684d6
      由 Li Zefan 提交于 
      Use DECLARE_EVENT_CLASS to remove duplicate code:

   text    data     bss     dec     hex filename
  29854    1980     128   31962    7cda kernel/module.o.old
  28750    1980     128   30858    788a kernel/module.o

Two events are converted:

  module_refcnt: module_get, module_put

No change in functionality.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0E283B.3010508@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      925684d6
    • I
      events: Rename TRACE_EVENT_TEMPLATE() to DECLARE_EVENT_CLASS() · 091ad365
      由 Ingo Molnar 提交于 
      It is not quite obvious at first sight what TRACE_EVENT_TEMPLATE
does: does it define an event as well beyond defining a template?

To clarify this, rename it to DECLARE_EVENT_CLASS, which follows
the various 'DECLARE_*()' idioms we already have in the kernel:

  DECLARE_EVENT_CLASS(class)

    DEFINE_EVENT(class, event1)
    DEFINE_EVENT(class, event2)
    DEFINE_EVENT(class, event3)

To complete this logic we should also rename TRACE_EVENT() to:

  DEFINE_SINGLE_EVENT(single_event)

... but in a more quiet moment of the kernel cycle.

Cc: Pekka Enberg <penberg@cs.helsinki.fi>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4B0E286A.2000405@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      091ad365
  7. 25 11月, 2009 3 次提交
    • S
      tracing: Convert some sched trace events to DEFINE_EVENT and _PRINT · 75ec29ab
      由 Steven Rostedt 提交于 
      Converting some of the scheduler trace events to use the
TRACE_EVENT_TEMPLATE, DEFINE_EVENT and DEFINE_EVENT_PRINT helped to
save some space:

$ size kernel/sched.o-*
   text	   data	    bss	    dec	    hex	filename
  79299	   6776	   2520	  88595	  15a13	kernel/sched.o-notrace
 101941	  11896	   2584	 116421	  1c6c5	kernel/sched.o-templ
 104779	  11896	   2584	 119259	  1d1db	kernel/sched.o-trace

sched.o-notrace is without any tracepoints compiled
sched.o-templ is with this patch
sched.o-trace is the tracepoints before this patch

The trace events converted to DEFINE_EVENT:

sched_wakeup, sched_wakeup_new, sched_process_free, sched_process_exit,
and sched_stat_wait.

The trace events converted to DEFINE_EVENT_PRINT:

sched_stat_sleep and sched_stat_iowait.

Note, since the TRACE_EVENT_TEMPLATE always uses a print, the
sched_stat_wait print format is defined in the template and this
template is used by sched_stat_sleep and sched_stat_iowait. But the
later two override the print format.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      75ec29ab
    • S
      tracing: Create new DEFINE_EVENT_PRINT · e5bc9721
      由 Steven Rostedt 提交于 
      After creating the TRACE_EVENT_TEMPLATE I started to look at other
trace points to see what duplication was made. I noticed that there
are several trace points where they are almost identical except for
the name and the output format. Since TRACE_EVENT_TEMPLATE was successful
in bringing down the size of trace events, I added a DEFINE_EVENT_PRINT.

DEFINE_EVENT_PRINT is used just like DEFINE_EVENT is. That is, the
DEFINE_EVENT_PRINT also uses a TRACE_EVENT_TEMPLATE, but it allows the
developer to overwrite the print format. If there are two or more
TRACE_EVENTS that are identical except for the name and print, then
they can be converted to use a TRACE_EVENT_TEMPLATE. Since the
TRACE_EVENT_TEMPLATE already does the print output, the first trace event
would have its print format held in the TRACE_EVENT_TEMPLATE and
be defined with a DEFINE_EVENT. The rest will use the DEFINE_EVENT_PRINT
and override the print format.

Converting the sched trace points to both DEFINE_EVENT and
DEFINE_EVENT_PRINT. Five were converted to DEFINE_EVENT and two were
converted to DEFINE_EVENT_PRINT.

I was able to get the following:

$ size kernel/sched.o-*
   text	   data	    bss	    dec	    hex	filename
  79299	   6776	   2520	  88595	  15a13	kernel/sched.o-notrace
 101941	  11896	   2584	 116421	  1c6c5	kernel/sched.o-templ
 104779	  11896	   2584	 119259	  1d1db	kernel/sched.o-trace

sched.o-notrace is the scheduler compiled with no trace points.
sched.o-templ is with the use of DEFINE_EVENT and DEFINE_EVENT_PRINT
sched.o-trace is the current trace events.
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      e5bc9721
    • S
      tracing: Create new TRACE_EVENT_TEMPLATE · ff038f5c
      由 Steven Rostedt 提交于 
      There are some places in the kernel that define several tracepoints and
they are all identical besides the name. The code to enable, disable and
record is created for every trace point even if most of the code is
identical.

This patch adds TRACE_EVENT_TEMPLATE that lets the developer create
a template TRACE_EVENT and create trace points with DEFINE_EVENT, which
is based off of a given template. Each trace point used by this
will share most of the code, and bring down the size of the kernel
when there are several duplicate events.

Usage is:

TRACE_EVENT_TEMPLATE(name, proto, args, tstruct, assign, print);

Which would be the same as defining a normal TRACE_EVENT.

To create the trace events that the trace points will use:

DEFINE_EVENT(template, name, proto, args) is done. The template
is the name of the TRACE_EVENT_TEMPLATE to use. The name is the
name of the trace point. The parameters proto and args must be the same
as the proto and args of the template. If they are not the same,
then a compile error will result. I tried hard removing this duplication
but the C preprocessor is not powerful enough (or my CPP magic
experience points is not at a high enough level) to not need them.

A lot of trace events are coming in with new XFS development. Most of
the trace points are identical except for the name. The following shows
the advantage of having TRACE_EVENT_TEMPLATE:

$ size fs/xfs/xfs.o.*
    text          data     bss     dec     hex filename
  452114          2788    3520  458422   6feb6 fs/xfs/xfs.o.old
  638482         38116    3744  680342   a6196 fs/xfs/xfs.o.template
  996954         38116    4480 1039550   fdcbe fs/xfs/xfs.o.trace

xfs.o.old is without any tracepoints.
xfs.o.template uses the new TRACE_EVENT_TEMPLATE.
xfs.o.trace uses the current TRACE_EVENT macros.
Requested-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>
      ff038f5c
  9. 24 11月, 2009 2 次提交
  11. 23 11月, 2009 1 次提交
  13. 22 11月, 2009 2 次提交
    • F
      hw-breakpoints: Separate the kernel part from breakpoint headers · 5093ebad
      由 Frederic Weisbecker 提交于 
      So that we can include this header from userspace tools, like
perf tools, to get the breakpoint types and len definitions.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
LKML-Reference: <1258863695-10464-4-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      5093ebad
    • F
      tracing: Use the perf recursion protection from trace event · ce71b9df
      由 Frederic Weisbecker 提交于 
      When we commit a trace to perf, we first check if we are
recursing in the same buffer so that we don't mess-up the buffer
with a recursing trace. But later on, we do the same check from
perf to avoid commit recursion. The recursion check is desired
early before we touch the buffer but we want to do this check
only once.

Then export the recursion protection from perf and use it from
the trace events before submitting a trace.

v2: Put appropriate Reported-by tag
Reported-by: NPeter Zijlstra <peterz@infradead.org>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Jason Baron <jbaron@redhat.com>
LKML-Reference: <1258864015-10579-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      ce71b9df
  15. 21 11月, 2009 2 次提交
  17. 16 11月, 2009 1 次提交
    • P
      perf_event: Optimize perf_output_lock() · 559fdc3c
      由 Peter Zijlstra 提交于 
      The purpose of perf_output_{un,}lock() is to:

 1) avoid publishing incomplete data
    [ possible when publishing a head that is ahead of an entry
      that is still being written ]

 2) guarantee fwd progress
    [ a simple refcount on pending writers doesn't need to drop to
      0, making it so would end up implementing something like forced
      quiecent states of RCU ]

To satisfy the above without undue complexity it serializes
between CPUs, this means that a pending writer can only be the
same cpu in a nested context, and since (under normal operation)
a cpu always makes progress we're good -- if the head is only
published when the bottom  most writer completes.

Now we don't need to disable IRQs in order to serialize between
CPUs, disabling preemption ought to be sufficient, esp since we
already deal with nesting due to NMIs.

This avoids potentially expensive (and needless) local IRQ
disable/enable ops.
Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <1258373161.26714.254.camel@laptop>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      559fdc3c
  19. 14 11月, 2009 3 次提交
  21. 13 11月, 2009 1 次提交
  23. 12 11月, 2009 3 次提交
  25. 11 11月, 2009 1 次提交
  27. 08 11月, 2009 2 次提交
    • F
      hw-breakpoints: Rewrite the hw-breakpoints layer on top of perf events · 24f1e32c
      由 Frederic Weisbecker 提交于 
      This patch rebase the implementation of the breakpoints API on top of
perf events instances.

Each breakpoints are now perf events that handle the
register scheduling, thread/cpu attachment, etc..

The new layering is now made as follows:

       ptrace       kgdb      ftrace   perf syscall
          \          |          /         /
           \         |         /         /
                                        /
            Core breakpoint API        /
                                      /
                     |               /
                     |              /

              Breakpoints perf events

                     |
                     |

               Breakpoints PMU ---- Debug Register constraints handling
                                    (Part of core breakpoint API)
                     |
                     |

             Hardware debug registers

Reasons of this rewrite:

- Use the centralized/optimized pmu registers scheduling,
  implying an easier arch integration
- More powerful register handling: perf attributes (pinned/flexible
  events, exclusive/non-exclusive, tunable period, etc...)

Impact:

- New perf ABI: the hardware breakpoints counters
- Ptrace breakpoints setting remains tricky and still needs some per
  thread breakpoints references.

Todo (in the order):

- Support breakpoints perf counter events for perf tools (ie: implement
  perf_bpcounter_event())
- Support from perf tools

Changes in v2:

- Follow the perf "event " rename
- The ptrace regression have been fixed (ptrace breakpoint perf events
  weren't released when a task ended)
- Drop the struct hw_breakpoint and store generic fields in
  perf_event_attr.
- Separate core and arch specific headers, drop
  asm-generic/hw_breakpoint.h and create linux/hw_breakpoint.h
- Use new generic len/type for breakpoint
- Handle off case: when breakpoints api is not supported by an arch

Changes in v3:

- Fix broken CONFIG_KVM, we need to propagate the breakpoint api
  changes to kvm when we exit the guest and restore the bp registers
  to the host.

Changes in v4:

- Drop the hw_breakpoint_restore() stub as it is only used by KVM
- EXPORT_SYMBOL_GPL hw_breakpoint_restore() as KVM can be built as a
  module
- Restore the breakpoints unconditionally on kvm guest exit:
  TIF_DEBUG_THREAD doesn't anymore cover every cases of running
  breakpoints and vcpu->arch.switch_db_regs might not always be
  set when the guest used debug registers.
  (Waiting for a reliable optimization)

Changes in v5:

- Split-up the asm-generic/hw-breakpoint.h moving to
  linux/hw_breakpoint.h into a separate patch
- Optimize the breakpoints restoring while switching from kvm guest
  to host. We only want to restore the state if we have active
  breakpoints to the host, otherwise we don't care about messed-up
  address registers.
- Add asm/hw_breakpoint.h to Kbuild
- Fix bad breakpoint type in trace_selftest.c

Changes in v6:

- Fix wrong header inclusion in trace.h (triggered a build
  error with CONFIG_FTRACE_SELFTEST
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Jan Kiszka <jan.kiszka@web.de>
Cc: Jiri Slaby <jirislaby@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Paul Mundt <lethal@linux-sh.org>
      24f1e32c
    • F
      tracing, perf_events: Protect the buffer from recursion in perf · 444a2a3b
      由 Frederic Weisbecker 提交于 
      While tracing using events with perf, if one enables the
lockdep:lock_acquire event, it will infect every other perf
trace events.

Basically, you can enable whatever set of trace events through
perf but if this event is part of the set, the only result we
can get is a long list of lock_acquire events of rcu read lock,
and only that.

This is because of a recursion inside perf.

1) When a trace event is triggered, it will fill a per cpu
   buffer and submit it to perf.

2) Perf will commit this event but will also protect some data
   using rcu_read_lock

3) A recursion appears: rcu_read_lock triggers a lock_acquire
   event that will fill the per cpu event and then submit the
   buffer to perf.

4) Perf detects a recursion and ignores it

5) Perf continues its work on the previous event, but its buffer
   has been overwritten by the lock_acquire event, it has then
   been turned into a lock_acquire event of rcu read lock

Such scenario also happens with lock_release with
rcu_read_unlock().

We could turn the rcu_read_lock() into __rcu_read_lock() to drop
the lock debugging from perf fast path, but that would make us
lose the rcu debugging and that doesn't prevent from other
possible kind of recursion from perf in the future.

This patch adds a recursion protection based on a counter on the
perf trace per cpu buffers to solve the problem.

-v2: Fixed lost whitespace, added reviewed-by tag
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: NMasami Hiramatsu <mhiramat@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Jason Baron <jbaron@redhat.com>
LKML-Reference: <1257477185-7838-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>
      444a2a3b