tracing: Fix race where histograms can be called before the event

commit 94eedf3dded5 ("tracing: Fix race where eprobes can be called before
the event") fixed an issue where if an event is soft disabled, and the
trigger is being added, there's a small window where the event sees that
there's a trigger but does not see that it requires reading the event yet,
and then calls the trigger with the record == NULL.

This could be solved with adding memory barriers in the hot path, or to
make sure that all the triggers requiring a record check for NULL. The
latter was chosen.

Commit 94eedf3dded5 set the eprobe trigger handle to check for NULL, but
the same needs to be done with histograms.

Link: https://lore.kernel.org/linux-trace-kernel/[email protected]/
Link: https://lore.kernel.org/linux-trace-kernel/[email protected]

Cc: Tom Zanussi <[email protected]>
Cc: [email protected]
Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events")
Reported-by: Masami Hiramatsu (Google) <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Steven Rostedt (Google) <[email protected]>

0 files changed, 0 insertions, 0 deletions