lkml.org 
[lkml]   [2022]   [Nov]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] tracing: Fix race where histograms can be called before the event
On Wed, 23 Nov 2022 16:43:23 -0500
Steven Rostedt <rostedt@goodmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
>
> 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/20221118211809.701d40c0f8a757b0df3c025a@kernel.org/
>
> Cc: stable@vger.kernel.org
> Fixes: 7491e2c442781 ("tracing: Add a probe that attaches to trace events")
> Reported-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

I confirmed that other trigger callbacks only use the event_trigger_data,
So this looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thank you!

> ---
> kernel/trace/trace_events_hist.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
> index 087c19548049..1c82478e8dff 100644
> --- a/kernel/trace/trace_events_hist.c
> +++ b/kernel/trace/trace_events_hist.c
> @@ -5143,6 +5143,9 @@ static void event_hist_trigger(struct event_trigger_data *data,
> void *key = NULL;
> unsigned int i;
>
> + if (unlikely(!rbe))
> + return;
> +
> memset(compound_key, 0, hist_data->key_size);
>
> for_each_hist_key_field(i, hist_data) {
> --
> 2.35.1
>


--
Masami Hiramatsu (Google) <mhiramat@kernel.org>

\
 
 \ /
  Last update: 2022-11-24 00:39    [W:0.034 / U:0.464 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site