Skip to content

Commit

Permalink
perf/core: Fix perf_sched_count derailment
Browse files Browse the repository at this point in the history
The error path in perf_event_open() is such that asking for a sampling
event on a PMU that doesn't generate interrupts will end up in dropping
the perf_sched_count even though it hasn't been incremented for this
event yet.

Given a sufficient amount of these calls, we'll end up disabling
scheduler's jump label even though we'd still have active events in the
system, thereby facilitating the arrival of the infernal regions upon us.

I'm fixing this by moving account_event() inside perf_event_alloc().

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: vince@deater.net
Link: http://lkml.kernel.org/r/1456917854-29427-1-git-send-email-alexander.shishkin@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
  • Loading branch information
Alexander Shishkin authored and Ingo Molnar committed Mar 8, 2016
1 parent b9461ba commit 927a557
Showing 1 changed file with 3 additions and 4 deletions.
7 changes: 3 additions & 4 deletions kernel/events/core.c
Original file line number Diff line number Diff line change
Expand Up @@ -8000,6 +8000,9 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
}
}

/* symmetric to unaccount_event() in _free_event() */
account_event(event);

return event;

err_per_task:
Expand Down Expand Up @@ -8363,8 +8366,6 @@ SYSCALL_DEFINE5(perf_event_open,
}
}

account_event(event);

/*
* Special case software events and allow them to be part of
* any hardware group.
Expand Down Expand Up @@ -8661,8 +8662,6 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
/* Mark owner so we could distinguish it from user events. */
event->owner = TASK_TOMBSTONE;

account_event(event);

ctx = find_get_context(event->pmu, task, event);
if (IS_ERR(ctx)) {
err = PTR_ERR(ctx);
Expand Down

0 comments on commit 927a557

Please sign in to comment.