linux-kernel - Re: [PATCH] tracing/timerlat: Check tlat_var for NULL in timerlat_fd

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Message-ID: <20240904102104.6f2a35af@gandalf.local.home>
Date: Wed, 4 Sep 2024 10:21:04 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Tomas Glozar <tglozar@...hat.com>
Cc: linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org,
 jkacur@...hat.com, "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>
Subject: Re: [PATCH] tracing/timerlat: Check tlat_var for NULL in
 timerlat_fd_release

On Tue, 3 Sep 2024 14:47:42 +0200
Tomas Glozar <tglozar@...hat.com> wrote:

> I suggest using the workaround suggested in
> https://lore.kernel.org/linux-trace-kernel/20240823125426.404f2705@gandalf.local.home
> for the time being. Together with the patch that adds locks around
> stopping the threads
> (https://patchwork.kernel.org/project/linux-trace-kernel/patch/20240823102816.5e55753b@gandalf.local.home/),
> this should prevent the kernel panic at least until we have a solution
> for the race itself.

When running my tests, the second one would end up deadlocking and
triggering lockdep. I found a way to do basically the same thing with a
cpumask and no added locking. I'm currently testing it and will be sending
out a patch later today (if it passes the tests).

-- Steve