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authorSteven Rostedt (VMware) <rostedt@goodmis.org>2017-10-17 14:55:24 -0400
committerSteven Rostedt (VMware) <rostedt@goodmis.org>2017-10-17 14:55:24 -0400
commit6575257c60e1a26a5319ccf2b5ce5b6449001017 (patch)
treeb6404781ed926174017f99758ad84d57a1b19606 /samples/trace_events
parentf39b536ce9248e9799ff900358d6f073ab2e6c55 (diff)
downloadlinux-6575257c60e1a26a5319ccf2b5ce5b6449001017.tar.gz
tracing/samples: Fix creation and deletion of simple_thread_fn creation
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. Cc: stable@vger.kernel.org Fixes: 7496946a8 ("tracing: Add samples of DECLARE_EVENT_CLASS() and DEFINE_EVENT()") Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Diffstat (limited to 'samples/trace_events')
-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);
}