perfcounters: tweak group scheduling

Impact: schedule in groups atomically

If there are multiple groups in a task, make sure they are scheduled
in and out atomically.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 13 insertions, 3 deletions

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index aab6c123b02c..f8a4d9a5d5d3 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -367,21 +367,26 @@ counter_sched_in(struct perf_counter *counter,
         ctx->nr_active++;
 }
 
-static void
+static int
 group_sched_in(struct perf_counter *group_counter,
                struct perf_cpu_context *cpuctx,
                struct perf_counter_context *ctx,
                int cpu)
 {
         struct perf_counter *counter;
+        int was_group = 0;
 
         counter_sched_in(group_counter, cpuctx, ctx, cpu);
 
         /*
          * Schedule in siblings as one group (if any):
          */
-        list_for_each_entry(counter, &group_counter->sibling_list, list_entry)
+        list_for_each_entry(counter, &group_counter->sibling_list, list_entry) {
                 counter_sched_in(counter, cpuctx, ctx, cpu);
+                was_group = 1;
+        }
+
+        return was_group;
 }
 
 /*
@@ -416,7 +421,12 @@ void perf_counter_task_sched_in(struct task_struct *task, int cpu)
                 if (counter->cpu != -1 && counter->cpu != cpu)
                         continue;
 
-                group_sched_in(counter, cpuctx, ctx, cpu);
+                /*
+                 * If we scheduled in a group atomically and
+                 * exclusively, break out:
+                 */
+                if (group_sched_in(counter, cpuctx, ctx, cpu))
+                        break;
         }
         spin_unlock(&ctx->lock);