tracing/kprobe: Wait for disabling all running kprobe handlers
Wait for disabling all running kprobe handlers when a kprobe
event is disabled, since the caller, trace_remove_event_call()
supposes that a removing event is disabled completely by
disabling the event.
With this change, ftrace can ensure that there is no running
event handlers after disabling it.
Link: http://lkml.kernel.org/r/20130709093526.20138.93100.stgit@mhiramat-M0-7522
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index ae6ce83..3811487 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -243,11 +243,11 @@
static int
disable_trace_probe(struct trace_probe *tp, struct ftrace_event_file *file)
{
+ struct event_file_link *link = NULL;
+ int wait = 0;
int ret = 0;
if (file) {
- struct event_file_link *link;
-
link = find_event_file_link(tp, file);
if (!link) {
ret = -EINVAL;
@@ -255,10 +255,7 @@
}
list_del_rcu(&link->list);
- /* synchronize with kprobe_trace_func/kretprobe_trace_func */
- synchronize_sched();
- kfree(link);
-
+ wait = 1;
if (!list_empty(&tp->files))
goto out;
@@ -271,8 +268,22 @@
disable_kretprobe(&tp->rp);
else
disable_kprobe(&tp->rp.kp);
+ wait = 1;
}
out:
+ if (wait) {
+ /*
+ * Synchronize with kprobe_trace_func/kretprobe_trace_func
+ * to ensure disabled (all running handlers are finished).
+ * This is not only for kfree(), but also the caller,
+ * trace_remove_event_call() supposes it for releasing
+ * event_call related objects, which will be accessed in
+ * the kprobe_trace_func/kretprobe_trace_func.
+ */
+ synchronize_sched();
+ kfree(link); /* Ignored if link == NULL */
+ }
+
return ret;
}
