Commit-ID: e8d8a90fc5014e4cdcf1de2f320081d26c7f440f
Gitweb: http://git.kernel.org/tip/e8d8a90fc5014e4cdcf1de2f320081d26c7f440f
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 18 Mar 2016 17:31:27 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Mon, 21 Mar 2016 09:08:17 +0100
perf/x86/BTS: Fix RCU usage
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@xxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Brian Gerst <brgerst@xxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/events/intel/ds.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index ce7211a..8584b90 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -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, ®s);
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;
}
--
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