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perf/x86/BTS: Fix RCU usage

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This splat reminds us:

[ 8166.045595] [ INFO: suspicious RCU usage. ]

[ 8166.168972]  [<ffffffff81127837>] lockdep_rcu_suspicious+0xe7/0x120
[ 8166.175966]  [<ffffffff811e0bae>] perf_callchain+0x23e/0x250
[ 8166.182280]  [<ffffffff811dda3d>] perf_prepare_sample+0x27d/0x350
[ 8166.189082]  [<ffffffff8100f503>] intel_pmu_drain_bts_buffer+0x133/0x200

... that as the core code does, one should hold rcu_read_lock() over that
entire BTS event-output generation sequence as well.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2016-03-18 17:31:27 +01:00 committed by Ingo Molnar
parent 91a612eea9
commit e8d8a90fc5
1 changed files with 4 additions and 1 deletions
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5
arch/x86/events/intel/ds.c
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@ -570,11 +570,12 @@ int intel_pmu_drain_bts_buffer(void)
* We will overwrite the from and to address before we output
* the sample.
*/
rcu_read_lock();
perf_prepare_sample(&header, &data, event, &regs);
if (perf_output_begin(&handle, event, header.size *
(top - base - skip)))
return 1;
goto unlock;
for (at = base; at < top; at++) {
/* Filter out any records that contain kernel addresses. */
@ -593,6 +594,8 @@ int intel_pmu_drain_bts_buffer(void)
/* There's new data available. */
event->hw.interrupts++;
event->pending_kill = POLL_IN;
unlock:
rcu_read_unlock();
return 1;
}