On Wed, 12 Aug 2020 14:52:59 -0600
dann frazier <dann.frazier@xxxxxxxxxxxxx> wrote:
> From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
>
> commit 7ef282e05132d56b6f6b71e3873f317664bea78b upstream
>
> If a process has the trace_pipe open on a trace_array, the current tracer
> for that trace array should not be changed. This was original enforced by a
> global lock, but when instances were introduced, it was moved to the
> current_trace. But this structure is shared by all instances, and a
> trace_pipe is for a single instance. There's no reason that a process that
> has trace_pipe open on one instance should prevent another instance from
> changing its current tracer. Move the reference counter to the trace_array
> instead.
>
> This is marked as "Fixes" but is more of a clean up than a true fix.
> Backport if you want, but its not critical.
A note to stable maintainers. I originally thought this was just a
clean up, but it was then found that it actually does fix a bug.
-- Steve
>
> Fixes: cf6ab6d9143b1 ("tracing: Add ref count to tracer for when they are being read by pipe")
> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
>
