Commit-ID: c44d70a340554a33071339064a303ac0f1a31623
Gitweb: http://git.kernel.org/tip/c44d70a340554a33071339064a303ac0f1a31623
Author: Ingo Molnar <mingo@xxxxxxx>
AuthorDate: Sun, 17 May 2009 11:24:08 +0200
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 20 May 2009 00:22:30 +0200
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@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
include/linux/perf_counter.h | 1 +
kernel/perf_counter.c | 10 +++++++++-
2 files changed, 10 insertions(+), 1 deletions(-)
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index c8c1dfc..13cb2fb 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -508,6 +508,7 @@ struct perf_counter_context {
int nr_counters;
int nr_active;
int is_active;
+ int rr_allowed;
struct task_struct *task;
/*
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 7af16d1..4d8f973 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);
}
--
To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
|