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  1. Aug 14, 2009
  2. Aug 13, 2009
    • Peter Zijlstra's avatar
      perf_counter: Report the cloning task as parent on perf_counter_fork() · 94d5d1b2
      Peter Zijlstra authored
      
      
      A bug in (9f498cc5: perf_counter: Full task tracing) makes
      profiling multi-threaded apps it go belly up.
      
      [ output as: (PID:TID):(PPID:PTID) ]
      
       # ./perf report -D | grep FORK
      0x4b0 [0x18]: PERF_EVENT_FORK: (3237:3237):(3236:3236)
      0xa10 [0x18]: PERF_EVENT_FORK: (3237:3238):(3236:3236)
      0xa70 [0x18]: PERF_EVENT_FORK: (3237:3239):(3236:3236)
      0xad0 [0x18]: PERF_EVENT_FORK: (3237:3240):(3236:3236)
      0xb18 [0x18]: PERF_EVENT_FORK: (3237:3241):(3236:3236)
      
      Shows us that the test (27d028de perf report: Update for the new
      FORK/EXIT events) in builtin-report.c:
      
              /*
               * A thread clone will have the same PID for both
               * parent and child.
               */
              if (thread == parent)
                      return 0;
      
      Will clearly fail.
      
      The problem is that perf_counter_fork() reports the actual
      parent, instead of the cloning thread.
      
      Fixing that (with the below patch), yields:
      
       # ./perf report -D | grep FORK
      0x4c8 [0x18]: PERF_EVENT_FORK: (1590:1590):(1589:1589)
      0xbd8 [0x18]: PERF_EVENT_FORK: (1590:1591):(1590:1590)
      0xc80 [0x18]: PERF_EVENT_FORK: (1590:1592):(1590:1590)
      0x3338 [0x18]: PERF_EVENT_FORK: (1590:1593):(1590:1590)
      0x66b0 [0x18]: PERF_EVENT_FORK: (1590:1594):(1590:1590)
      
      Which both makes more sense and doesn't confuse perf report
      anymore.
      
      Reported-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
      Cc: paulus@samba.org
      Cc: Anton Blanchard <anton@samba.org>
      Cc: Arjan van de Ven <arjan@infradead.org>
      LKML-Reference: <1250172882.5241.62.camel@twins>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      94d5d1b2
    • Peter Zijlstra's avatar
      perf_counter: Fix an ipi-deadlock · 970892a9
      Peter Zijlstra authored
      
      
      perf_pending_counter() is called from IRQ context and will call
      perf_counter_disable(), however perf_counter_disable() uses
      smp_call_function_single() which doesn't fancy being used with
      IRQs disabled due to IPI deadlocks.
      
      Fix this by making it use the local __perf_counter_disable()
      call and teaching the counter_sched_out() code about pending
      disables as well.
      
      This should cover the case where a counter migrates before the
      pending queue gets processed.
      
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Corey J Ashford <cjashfor@us.ibm.com>
      Cc: Paul Mackerras <paulus@samba.org>
      Cc: stephane eranian <eranian@googlemail.com>
      LKML-Reference: <20090813103655.244097721@chello.nl>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      970892a9