path: root/samples
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authorLinus Torvalds <torvalds@linux-foundation.org>2017-10-18 06:43:30 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2017-10-18 06:43:30 -0400
commit503f7e297d76bf109533eef3287ad821f05e47a4 (patch)
treea47e1315e9a3385c24ea1dc7756594cda2fbbeb5 /samples
parentMerge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi (diff)
parenttracing/samples: Fix creation and deletion of simple_thread_fn creation (diff)
Merge tag 'trace-v4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fix from Steven Rostedt: "Testing a new trace event format, I triggered a bug by doing: # modprobe trace-events-sample # echo 1 > /sys/kernel/debug/tracing/events/sample-trace/enable # rmmod trace-events-sample This would cause an oops. The issue is that I added another trace event sample that reused a reg function of another trace event to create a thread to call the tracepoints. The problem was that the reg function couldn't handle nested calls (reg; reg; unreg; unreg;) and created two threads (instead of one) and only removed one on exit. This isn't a critical bug as the bug is only in sample code. But sample code should be free of known bugs to prevent others from copying it. This is why this is also marked for stable" * tag 'trace-v4.14-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: tracing/samples: Fix creation and deletion of simple_thread_fn creation
Diffstat (limited to 'samples')
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:
return 0;
void foo_bar_unreg(void)
- pr_info("Killing thread for foo_bar_fn\n");
- /* protect against module unloading */
+ if (--simple_thread_cnt)
+ goto out;
+ pr_info("Killing thread for foo_bar_fn\n");
if (simple_tsk_fn)
simple_tsk_fn = NULL;
+ out: