tracing/function: Avoid perf_trace_buf_*() if event_function.perf_eve…

…nts is empty perf_trace_buf_prepare() + perf_trace_buf_submit(head, task => NULL) make no sense if hlist_empty(head). Change perf_ftrace_function_call() to check event_function.perf_events beforehand. Link: http://lkml.kernel.org/r/[email protected] Acked-by: Peter Zijlstra <[email protected]> Signed-off-by: Oleg Nesterov <[email protected]> Signed-off-by: Steven Rostedt <[email protected]>
Baughn · Jul 19, 2013 · b8ebfd3 · b8ebfd3
1 parent d611851
commit b8ebfd3
Showing 1 changed file with 4 additions and 2 deletions.
diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
@@ -266,6 +266,10 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
 	struct pt_regs regs;
 	int rctx;
 
+	head = this_cpu_ptr(event_function.perf_events);
+	if (hlist_empty(head))
+		return;
+
 #define ENTRY_SIZE (ALIGN(sizeof(struct ftrace_entry) + sizeof(u32), \
 		    sizeof(u64)) - sizeof(u32))
 
@@ -279,8 +283,6 @@ perf_ftrace_function_call(unsigned long ip, unsigned long parent_ip,
 
 	entry->ip = ip;
 	entry->parent_ip = parent_ip;
-
-	head = this_cpu_ptr(event_function.perf_events);
 	perf_trace_buf_submit(entry, ENTRY_SIZE, rctx, 0,
 			      1, &regs, head, NULL);