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Wed, 04 Nov 2026 10:44:03 -0800 (PST) Received: from xps16 ([96.43.243.2]) by smtp.gmail.com with ESMTPSA id 5614622812f47-567a9fdfa53sm2199007b6e.15.2026.11.04.10.44.00 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Nov 2026 10:44:00 -0800 (PST) From: Jens Axboe To: stable@vger.kernel.org Subject: [PATCH 6.12.y 4/9] io_uring/io-wq: no new workers once the exit has begun Date: Wed, 4 Nov 2026 11:43:48 -0700 Message-ID: <20261104184353.516403-5-axboe@kernel.dk> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261104184353.516403-1-axboe@kernel.dk> References: <20261104184353.516403-1-axboe@kernel.dk> X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Josef Bacik Commit 47c68f925062a6013235d06add85a59f7d91e0fb upstream. io_wq_exit_start() sets IO_WQ_BIT_EXIT, but worker creation task_work queued before that stays queued until io_wq_exit_workers() cancels it. In between the task runs its task_work while canceling requests, and a worker can still get created. That's a problem for exec. begin_new_exec() calls io_uring_task_cancel() after de_thread(), when it's supposedly the only thread left, and io_wq_exit_workers() only waits for ->worker_done, which a worker completes before do_exit(). So the exiting worker is still in the thread group, using the mm, files and sighand, while exec replaces them. Easy to hit with a signal pending when create_io_thread() fails and the retry gets queued right before execve(). Cancel the queued creation task_work as soon as the exit bit is set. Pending work that isn't otherwise canceled now ends with -ECANCELED when the io-wq is destroyed, rather than depending on whether the task happened to run its task_work first. Fixes: 685fe7feedb9 ("io-wq: eliminate the need for a manager thread") Signed-off-by: Josef Bacik [axboe: the barrier is already upstream, see 0e5663856b69, only the cancel is new] Signed-off-by: Jens Axboe --- io_uring/io-wq.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/io_uring/io-wq.c b/io_uring/io-wq.c index e48239486dfe..181eecdb32c0 100644 --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -1320,6 +1320,12 @@ void io_wq_exit_start(struct io_wq *wq) set_bit(IO_WQ_BIT_EXIT, &wq->state); /* Pairs with task_work_add() in io_queue_worker_create(). */ smp_mb__after_atomic(); + /* + * No more workers from here on. The caller is going to run its task + * work, and on exec a thread that is created now would still be + * around, exiting, by the time that the caller must be on its own. + */ + io_wq_cancel_tw_create(wq); } static void io_wq_cancel_tw_create(struct io_wq *wq) -- 2.56.0