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>

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index aab6c123b02c2d771613e631cb5ed49aa7908664..f8a4d9a5d5d35e29f869907c2a07ce45f1ed0682 100644 (file)
--- 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);