1. 31 May, 2010 5 commits
    • Stephane Eranian's avatar
      perf_events: Fix event scheduling issues introduced by transactional API · 90151c35
      Stephane Eranian authored
      The transactional API patch between the generic and model-specific
      code introduced several important bugs with event scheduling, at
      least on X86. If you had pinned events, e.g., watchdog,  and were
      over-committing the PMU, you would get bogus counts. The bug was
      showing up on Intel CPU because events would move around more
      often that on AMD. But the problem also existed on AMD, though
      harder to expose.
      
      The issues were:
      
       - group_sched_in() was missing a cancel_txn() in the error path
      
       - cpuc->n_added was not properly maintained, leading to missing
         actions in hw_perf_enable(), i.e., n_running being 0. You cannot
         update n_added until you know the transaction has succeeded. In
         case of failed transaction n_added was not adjusted back.
      
       - in case of failed transactions, event_sched_out() was called
         and eventually invoked x86_disable_event() to touch the HW reg.
         But with transactions, on X86, event_sched_in() does not touch
         HW registers, it simply collects events into a list. Thus, you
         could end up calling x86_disable_event() on a counter which
         did not correspond to the current event when idx != -1.
      
      The patch modifies the generic and X86 code to avoid all those problems.
      
      First, we keep track of the number of events added last. In case the
      transaction fails, we substract them from n_added. This approach is
      necessary (as opposed to delaying updates to n_added) because not all
      event updates use the transaction API, e.g., single events.
      
      Second, we encapsulate the event_sched_in() and event_sched_out() in
      group_sched_in() inside the transaction. That makes the operations
      symmetrical and you can also detect that you are inside a transaction
      and skip the HW reg access by checking cpuc->group_flag.
      
      With this patch, you can now overcommit the PMU even with pinned
      system-wide events present and still get valid counts.
      Signed-off-by: default avatarStephane Eranian <eranian@google.com>
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      LKML-Reference: <1274796225.5882.1389.camel@twins>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      90151c35
    • Peter Zijlstra's avatar
      perf_events, trace: Fix perf_trace_destroy(), mutex went missing · 2e97942f
      Peter Zijlstra authored
      Steve spotted I forgot to do the destroy under event_mutex.
      Reported-by: default avatarSteven Rostedt <rostedt@goodmis.org>
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      LKML-Reference: <1274451913.1674.1707.camel@laptop>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      2e97942f
    • Peter Zijlstra's avatar
      perf_events, trace: Fix probe unregister race · 3771f077
      Peter Zijlstra authored
      tracepoint_probe_unregister() does not synchronize against the probe
      callbacks, so do that explicitly. This properly serializes the callbacks
      and the free of the data used therein.
      
      Also, use this_cpu_ptr() where possible.
      Acked-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      LKML-Reference: <1274438476.1674.1702.camel@laptop>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      3771f077
    • Peter Zijlstra's avatar
      perf_events: Fix races in group composition · 8a49542c
      Peter Zijlstra authored
      Group siblings don't pin each-other or the parent, so when we destroy
      events we must make sure to clean up all cross referencing pointers.
      
      In particular, for destruction of a group leader we must be able to
      find all its siblings and remove their reference to it.
      
      This means that detaching an event from its context must not detach it
      from the group, otherwise we can end up failing to clear all pointers.
      
      Solve this by clearly separating the attachment to a context and
      attachment to a group, and keep the group composed until we destroy
      the events.
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      LKML-Reference: <new-submission>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      8a49542c
    • Peter Zijlstra's avatar
      perf_events: Fix races and clean up perf_event and perf_mmap_data interaction · ac9721f3
      Peter Zijlstra authored
      In order to move toward separate buffer objects, rework the whole
      perf_mmap_data construct to be a more self-sufficient entity, one
      with its own lifetime rules.
      
      This greatly sanitizes the whole output redirection code, which
      was riddled with bugs and races.
      Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: <stable@kernel.org>
      LKML-Reference: <new-submission>
      Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      ac9721f3
  2. 30 May, 2010 26 commits
  3. 29 May, 2010 9 commits