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path: root/samples/trace_events/trace-events-sample.c
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Diffstat (limited to 'samples/trace_events/trace-events-sample.c')
-rw-r--r--samples/trace_events/trace-events-sample.c14
1 files changed, 11 insertions, 3 deletions
diff --git a/samples/trace_events/trace-events-sample.c b/samples/trace_events/trace-events-sample.c
index bc7fcf010a5b..446beb7ac48d 100644
--- a/samples/trace_events/trace-events-sample.c
+++ b/samples/trace_events/trace-events-sample.c
@@ -78,29 +78,37 @@ static int simple_thread_fn(void *arg)
}
static DEFINE_MUTEX(thread_mutex);
+static bool simple_thread_cnt;
int foo_bar_reg(void)
{
+ mutex_lock(&thread_mutex);
+ if (simple_thread_cnt++)
+ goto out;
+
pr_info("Starting thread for foo_bar_fn\n");
/*
* We shouldn't be able to start a trace when the module is
* unloading (there's other locks to prevent that). But
* for consistency sake, we still take the thread_mutex.
*/
- mutex_lock(&thread_mutex);
simple_tsk_fn = kthread_run(simple_thread_fn, NULL, "event-sample-fn");
+ out:
mutex_unlock(&thread_mutex);
return 0;
}
void foo_bar_unreg(void)
{
- pr_info("Killing thread for foo_bar_fn\n");
- /* protect against module unloading */
mutex_lock(&thread_mutex);
+ if (--simple_thread_cnt)
+ goto out;
+
+ pr_info("Killing thread for foo_bar_fn\n");
if (simple_tsk_fn)
kthread_stop(simple_tsk_fn);
simple_tsk_fn = NULL;
+ out:
mutex_unlock(&thread_mutex);
}