perf_counter: Sanitize counter->mutex

s/counter->mutex/counter->child_mutex/ and make sure its only
used to protect child_list.

The usage in __perf_counter_exit_task() doesn't appear to be
problematic since ctx->mutex also covers anything related to fd
tear-down.

Signed-off-by: Peter Zijlstra <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Corey Ashford <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: John Kacur <[email protected]>
LKML-Reference: <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 3 insertions, 4 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 23ddd29730f8..4ab8050eb9e8 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -452,9 +452,6 @@ struct perf_counter {
 	struct perf_counter_context	*ctx;
 	struct file			*filp;
 
-	struct perf_counter		*parent;
-	struct list_head		child_list;
-
 	/*
 	 * These accumulate total time (in nanoseconds) that children
 	 * counters have been enabled and running, respectively.
@@ -465,7 +462,9 @@ struct perf_counter {
 	/*
 	 * Protect attach/detach and child_list:
 	 */
-	struct mutex			mutex;
+	struct mutex			child_mutex;
+	struct list_head		child_list;
+	struct perf_counter		*parent;
 
 	int				oncpu;
 	int				cpu;