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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2017-10-17 14:55:24 -0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-11-08 10:08:32 +0100
commit86b0853f73912805d96b87d016599f59b64965f5 (patch)
tree8759aecdfd21821ebc63269c6c6b9424c325839a
parent8b2653de6f78741b6e5217fc74b538a7f67f1a82 (diff)
tracing/samples: Fix creation and deletion of simple_thread_fn creation
commit 6575257c60e1a26a5319ccf2b5ce5b6449001017 upstream. Commit 7496946a8 ("tracing: Add samples of DECLARE_EVENT_CLASS() and DEFINE_EVENT()") added template examples for all the events. It created a DEFINE_EVENT_FN() example which reused the foo_bar_reg and foo_bar_unreg functions. Enabling both the TRACE_EVENT_FN() and DEFINE_EVENT_FN() example trace events caused the foo_bar_reg to be called twice, creating the test thread twice. The foo_bar_unreg would remove it only once, even if it was called multiple times, leaving a thread existing when the module is unloaded, causing an oops. Add a ref count and allow foo_bar_reg() and foo_bar_unreg() be called by multiple trace events. Fixes: 7496946a8 ("tracing: Add samples of DECLARE_EVENT_CLASS() and DEFINE_EVENT()") Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-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 880a7d1d27d2..d69715d99e4d 100644
--- a/samples/trace_events/trace-events-sample.c
+++ b/samples/trace_events/trace-events-sample.c
@@ -78,28 +78,36 @@ static int simple_thread_fn(void *arg)
}
static DEFINE_MUTEX(thread_mutex);
+static bool simple_thread_cnt;
void 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);
}
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);
}