Commit 4ede1259 authored Apr 16, 2020 by Linus Torvalds

linux-trace

Pull tracing fix from Steven Rostedt:
 "This fixes a small race between allocating a snapshot buffer and
  setting the snapshot trigger.

  On a slow machine, the trigger can occur before the snapshot is
  allocated causing a warning to be displayed in the ring buffer, and no
  snapshot triggering. Reversing the allocation and the enabling of the
  trigger fixes the problem"

* tag 'trace-v5.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
  tracing: Fix the race between registering 'snapshot' event trigger and triggering 'snapshot' operation

parents 86d32f9a 0bbe7f71

kernel/trace/trace_events_trigger.c

+3 −7

Original line number	Diff line number	Diff line
		@@ -1088,14 +1088,10 @@ register_snapshot_trigger(char glob, struct event_trigger_ops ops,
		struct event_trigger_data *data,
		struct trace_event_file *file)
		{
		int ret = register_trigger(glob, ops, data, file);

		if (ret > 0 && tracing_alloc_snapshot_instance(file->tr) != 0) {
		unregister_trigger(glob, ops, data, file);
		ret = 0;
		}
		if (tracing_alloc_snapshot_instance(file->tr) != 0)
		return 0;

		return ret;
		return register_trigger(glob, ops, data, file);
		}

		static int

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