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authorFrederic Weisbecker <fweisbec@gmail.com>2010-05-20 21:28:34 +0200
committerFrederic Weisbecker <fweisbec@gmail.com>2010-05-20 21:28:34 +0200
commitacd35a463cb2a8d2b28e094d718cf6e653ad7191 (patch)
tree65f9392ef5b670eafa819138602a8c49458040ab
parentdfacc4d6c98b89609250269f518c1f54c30454ef (diff)
downloadlinux-2.6.34-ux500-acd35a463cb2a8d2b28e094d718cf6e653ad7191.tar.gz
perf: Fix forgotten preempt_enable by nested writers
A writer that gets a reference to the buffer handle disables preemption. When we put that reference, we check if we are the outer most writer and if not, we simply return and defer the head update to the outer most writer. The problem here is that preemption is only reenabled by the outer most, that produces preemption count imbalance for every nested writer that exit. So just don't forget to always re-enable preemption when we put the buffer reference, whoever we are. Fixes lots of sleeping in atomic warnings, visible with lock events recording. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Stephane Eranian <eranian@google.com> Cc: Robert Richter <robert.richter@amd.com>
-rw-r--r--kernel/perf_event.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 2a060be3b07..45b7aec5545 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -2933,7 +2933,7 @@ again:
*/
if (!local_dec_and_test(&data->nest))
- return;
+ goto out;
/*
* Publish the known good head. Rely on the full barrier implied
@@ -2954,6 +2954,7 @@ again:
if (handle->wakeup != local_read(&data->wakeup))
perf_output_wakeup(handle);
+ out:
preempt_enable();
}