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-rw-r--r--kernel/perf_counter.c11
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 534e20d..b8fe739 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1503,10 +1503,21 @@ static void perf_counter_enable_on_exec(struct task_struct *task)
*/
static void __perf_counter_read(void *info)
{
+ struct perf_cpu_context *cpuctx = &__get_cpu_var(perf_cpu_context);
struct perf_counter *counter = info;
struct perf_counter_context *ctx = counter->ctx;
unsigned long flags;
+ /*
+ * If this is a task context, we need to check whether it is
+ * the current task context of this cpu. If not it has been
+ * scheduled out before the smp call arrived. In that case
+ * counter->count would have been updated to a recent sample
+ * when the counter was scheduled out.
+ */
+ if (ctx->task && cpuctx->task_ctx != ctx)
+ return;
+
local_irq_save(flags);
if (ctx->is_active)
update_context_time(ctx);
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