linux-kernel - Re: [PATCH 01/12] task_work: Fix NMI race condition

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Message-ID: <20251001113145.72e10530@gandalf.local.home>
Date: Wed, 1 Oct 2025 11:31:45 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Peter Zijlstra <peterz@...radead.org>
Cc: jpoimboe@...nel.org, rostedt@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 01/12] task_work: Fix NMI race condition

On Wed, 24 Sep 2025 09:59:49 +0200
Peter Zijlstra <peterz@...radead.org> wrote:

>   __schedule()
>   // disable irqs
>       <NMI>
> 	  task_work_add(current, work, TWA_NMI_CURRENT);
>       </NMI>
>   // current = next;
>   // enable irqs
>       <IRQ>
> 	  task_work_set_notify_irq()
> 	  test_and_set_tsk_thread_flag(current,
>                                        TIF_NOTIFY_RESUME); // wrong task!
>       </IRQ>
>   // original task skips task work on its next return to user (or exit!)
> 
> Fixes: 466e4d801cd4 ("task_work: Add TWA_NMI_CURRENT as an additional notify mode.")
> Reported-by: Josh Poimboeuf <jpoimboe@...nel.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Reviewed-by: Steven Rostedt (Google) <rostedt@...dmis.org>

-- Steve