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Biederman" , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Hyunwoo Kim Subject: Re: [PATCH v2] posix-cpu-timers: Dequeue per-thread timers before exchange_tids() In-Reply-To: <87bjaicxm0.ffs@fw13> References: <87bjaicxm0.ffs@fw13> Date: Mon, 31 Aug 2026 18:19:05 +0200 Message-ID: <878q5mclfq.ffs@fw13> MIME-Version: 1.0 Content-Type: text/plain X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 127C140011 X-Stat-Signature: hxy5bsykdg6qfozo5bijyfw5tdt7tz8g X-HE-Tag: 1788193149-220085 X-HE-Meta: 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 cnpQ5Bau w3SP20ju51OPKWNW5p0i8k4wLJkD3zFhIj0ULOOL5OIULEdq9Op+ot1k6vqrGdi04/gs/FZ0Eo0WikHVDfhCrlHDiKZuz0RyYWkFBIDEZJ2IHT72JOMhn6rAWsaqyEE0NRuGrW60L1YFQDAi/ZmShn4vT5mdVnxTrvOxtsjxxZ2AaofViLfGsLgmOP9Jx6bT3Y9HR4Km3dFOnqBYFP0+9djSAO36Hg6r3fZMyZMNGvcbhfVftvvbV6xtARdTm5JMhFaadEK26kLF/FJZWOzerfo3Yc+fMkZeg06st9rZ5Y1lTmfDt7PyqCSDiCI1uACLy0MvU Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 31 2026 at 13:56, Thomas Gleixner wrote: > On Wed, Aug 26 2026 at 20:41, Hyunwoo Kim wrote: >> diff --git a/fs/exec.c b/fs/exec.c >> index 745f6eb5279e6..9b2d140bd9f2a 100644 >> --- a/fs/exec.c >> +++ b/fs/exec.c >> @@ -1003,6 +1003,18 @@ static int de_thread(struct task_struct *tsk) >> * the former thread group leader: >> */ >> >> +#ifdef CONFIG_POSIX_TIMERS >> + /* >> + * exchange_tids() hands this thread's PID to the old leader, >> + * which is reaped right after. The PID lookup in >> + * timer_lock_sighand() then fails while the per thread CPU >> + * timers are still queued here, so dequeue them first. >> + */ >> + spin_lock(lock); >> + posix_cpu_timers_exit(tsk); >> + spin_unlock(lock); >> +#endif >> + >> /* Become a process group leader with the old leader's pid. >> * The old leader becomes a thread of the this thread group. >> */ > > Similar to the other issue vs. POSIX timer signals this really wants to > be solved in exit() independent of non-leader exec(). Let me have a > look. Duh. That's about the non-leader itself.... Why did anyone think that swapping TIDs is a brilliant idea? I still think that this should be done differently. There is no point in doing the disarming in release_task(). Let me think some more.