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  1. 21 Jan, 2011 2 commits
    • Oleg Nesterov's avatar
      perf: perf_event_exit_task_context: s/rcu_dereference/rcu_dereference_raw/ · 806839b2
      Oleg Nesterov authored 
      In theory, almost every user of task->child->perf_event_ctxp[]
is wrong. find_get_context() can install the new context at any
moment, we need read_barrier_depends().

dbe08d82 "perf: Fix
find_get_context() vs perf_event_exit_task() race" added
rcu_dereference() into perf_event_exit_task_context() to make
the precedent, but this makes __rcu_dereference_check() unhappy.
Use rcu_dereference_raw() to shut up the warning.
Reported-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: acme@redhat.com
Cc: paulus@samba.org
Cc: stern@rowland.harvard.edu
Cc: a.p.zijlstra@chello.nl
Cc: fweisbec@gmail.com
Cc: roland@redhat.com
Cc: prasad@linux.vnet.ibm.com
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
LKML-Reference: <20110121174547.GA8796@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      806839b2
    • Peter Zijlstra's avatar
      perf: Annotate cpuctx->ctx.mutex to avoid a lockdep splat · 547e9fd7
      Peter Zijlstra authored 
      Lockdep spotted:

	loop_1b_instruc/1899 is trying to acquire lock:
	 (event_mutex){+.+.+.}, at: [<ffffffff810e1908>] perf_trace_init+0x3b/0x2f7

	but task is already holding lock:
	 (&ctx->mutex){+.+.+.}, at: [<ffffffff810eb45b>] perf_event_init_context+0xc0/0x218

	which lock already depends on the new lock.

	the existing dependency chain (in reverse order) is:

	-> #3 (&ctx->mutex){+.+.+.}:
	-> #2 (cpu_hotplug.lock){+.+.+.}:
	-> #1 (module_mutex){+.+...}:
	-> #0 (event_mutex){+.+.+.}:

But because the deadlock would be cpuhotplug (cpu-event) vs fork
(task-event) it cannot, in fact, happen. We can annotate this by giving the
perf_event_context used for the cpuctx a different lock class from those
used by tasks.
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      547e9fd7
  3. 19 Jan, 2011 3 commits
    • Anton Blanchard's avatar
      powerpc, perf: Fix frequency calculation for overflowing counters (FSL version) · 8c8a9b25
      Anton Blanchard authored 
      When fixing the frequency calculations for perf on powerpc I
forgot to fix the FSL version.

If we dont set event->hw.last_period the frequency to period
calculations in perf go haywire and we continually
throttle/unthrottle the PMU.
Signed-off-by: default avatarAnton Blanchard <anton@samba.org>
Acked-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110118214404.2f42e634@kryten>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      8c8a9b25
    • Oleg Nesterov's avatar
      perf: Fix perf_event_init_task()/perf_event_free_task() interaction · 8550d7cb
      Oleg Nesterov authored 
      perf_event_init_task() should clear child->perf_event_ctxp[]
before anything else. Otherwise, if
perf_event_init_context(perf_hw_context) fails,
perf_event_free_task() can free perf_event_ctxp[perf_sw_context]
copied from parent->perf_event_ctxp[] by dup_task_struct().

Also move the initialization of perf_event_mutex and
perf_event_list from perf_event_init_context() to
perf_event_init_context().
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
LKML-Reference: <20110119182228.GC12183@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      8550d7cb
    • Oleg Nesterov's avatar
      perf: Fix find_get_context() vs perf_event_exit_task() race · dbe08d82
      Oleg Nesterov authored 
      find_get_context() must not install the new perf_event_context
if the task has already passed perf_event_exit_task().

If nothing else, this means the memory leak. Initially
ctx->refcount == 2, it is supposed that
perf_event_exit_task_context() should participate and do the
necessary put_ctx().

find_lively_task_by_vpid() checks PF_EXITING but this buys
nothing, by the time we call find_get_context() this task can be
already dead. To the point, cmpxchg() can succeed when the task
has already done the last schedule().

Change find_get_context() to populate task->perf_event_ctxp[]
under task->perf_event_mutex, this way we can trust PF_EXITING
because perf_event_exit_task() takes the same mutex.

Also, change perf_event_exit_task_context() to use
rcu_dereference(). Probably this is not strictly needed, but
with or without this change find_get_context() can race with
setup_new_exec()->perf_event_exit_task(), rcu_dereference()
looks better.
Signed-off-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Prasad <prasad@linux.vnet.ibm.com>
Cc: Roland McGrath <roland@redhat.com>
LKML-Reference: <20110119182207.GB12183@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      dbe08d82
  5. 18 Jan, 2011 35 commits
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