1 files changed, 15 insertions, 0 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 534e20d14d63..36f65e2b8b57 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);
@@ -2008,6 +2019,10 @@ int perf_counter_task_disable(void)
         return 0;
 }
 
+#ifndef PERF_COUNTER_INDEX_OFFSET
+# define PERF_COUNTER_INDEX_OFFSET 0
+#endif
+
 static int perf_counter_index(struct perf_counter *counter)
 {
         if (counter->state != PERF_COUNTER_STATE_ACTIVE)