Commit 5137f623 authored by Alexander Shishkin's avatar Alexander Shishkin Committed by Ben Hutchings

perf/core: Fix perf_sched_count derailment

commit 927a5570 upstream.

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: default avatarAlexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.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.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: default avatarBen Hutchings <ben@decadent.org.uk>
parent 49d9f61a
......@@ -6975,6 +6975,9 @@ perf_event_alloc(struct perf_event_attr *attr, int cpu,
}
}
/* symmetric to unaccount_event() in _free_event() */
account_event(event);
return event;
err_pmu:
......@@ -7276,8 +7279,6 @@ SYSCALL_DEFINE5(perf_event_open,
}
}
account_event(event);
/*
* Special case software events and allow them to be part of
* any hardware group.
......@@ -7486,8 +7487,6 @@ perf_event_create_kernel_counter(struct perf_event_attr *attr, int cpu,
goto err;
}
account_event(event);
ctx = find_get_context(event->pmu, task, cpu);
if (IS_ERR(ctx)) {
err = PTR_ERR(ctx);
......
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