Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 16/67] tracing/samples: Fix creation and deletion of simple_thread_fn creation | Date | Mon, 6 Nov 2017 10:43:39 +0100 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt (VMware) <rostedt@goodmis.org>
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>
--- samples/trace_events/trace-events-sample.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-)
--- 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); }
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