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author | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2017-10-17 14:55:24 -0400 |
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committer | Steven Rostedt (VMware) <rostedt@goodmis.org> | 2017-10-17 14:55:24 -0400 |
commit | 6575257c60e1a26a5319ccf2b5ce5b6449001017 (patch) | |
tree | b6404781ed926174017f99758ad84d57a1b19606 | |
parent | f39b536ce9248e9799ff900358d6f073ab2e6c55 (diff) | |
download | linux-stable-6575257c60e1a26a5319ccf2b5ce5b6449001017.tar.gz linux-stable-6575257c60e1a26a5319ccf2b5ce5b6449001017.tar.bz2 linux-stable-6575257c60e1a26a5319ccf2b5ce5b6449001017.zip |
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>
-rw-r--r-- | samples/trace_events/trace-events-sample.c | 14 |
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); } |