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authorIngo Molnar <mingo@elte.hu>2009-05-17 11:24:08 +0200
committerIngo Molnar <mingo@elte.hu>2009-05-20 00:22:30 +0200
commitc44d70a340554a33071339064a303ac0f1a31623 (patch)
treea620d5b82a07b2e2c8c7c57d2e81d5bfdcdd4c25 /kernel
parent33b2fb303fe7f6b08bbb32f708e67b96eaa94a7a (diff)
perf_counter: fix counter inheritance race
Context rotation should not occur when we are in the middle of walking the counter list when inheriting counters ... [ Impact: fix occasionally incorrect perf stat results ] Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com> Cc: Arnaldo Carvalho de Melo <acme@redhat.com> Cc: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/perf_counter.c10
1 files changed, 9 insertions, 1 deletions
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 7af16d1c480..4d8f97375f3 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1120,7 +1120,8 @@ void perf_counter_task_tick(struct task_struct *curr, int cpu)
__perf_counter_task_sched_out(ctx);
rotate_ctx(&cpuctx->ctx);
- rotate_ctx(ctx);
+ if (ctx->rr_allowed)
+ rotate_ctx(ctx);
perf_counter_cpu_sched_in(cpuctx, cpu);
perf_counter_task_sched_in(curr, cpu);
@@ -3108,6 +3109,7 @@ __perf_counter_init_context(struct perf_counter_context *ctx,
mutex_init(&ctx->mutex);
INIT_LIST_HEAD(&ctx->counter_list);
INIT_LIST_HEAD(&ctx->event_list);
+ ctx->rr_allowed = 1;
ctx->task = task;
}
@@ -3348,6 +3350,9 @@ void perf_counter_init_task(struct task_struct *child)
*/
mutex_lock(&parent_ctx->mutex);
+ parent_ctx->rr_allowed = 0;
+ barrier(); /* irqs */
+
/*
* We dont have to disable NMIs - we are only looking at
* the list, not manipulating it:
@@ -3361,6 +3366,9 @@ void perf_counter_init_task(struct task_struct *child)
break;
}
+ barrier(); /* irqs */
+ parent_ctx->rr_allowed = 1;
+
mutex_unlock(&parent_ctx->mutex);
}