From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793207961; b=DTfshq/I4kRDb6PeSvWBb8Ce2CLL0DBumjtto0P8wcloOzhwKriekkr4VbCQ05e7FwC7 +0ABEv+6sk1hUnVWNjV2qlYwDHTrVret1QxsFacj8oxhEGl+LzutlbbA573usrXWqoFGO JZrlhzxIj55u28/vxIg3CBax/rZNT3QYnVfUBAeLGw9U8Xa5+fe3X9vjhfppFxPGyLLlW 7LQmhoadqGqDvgp3Sy+JvvqHG5FADMV++s6u91YP2KAqRAfE6qf8TdEMD1qW7IKV6IFwb 2Sfj7bpDUms22IEbqD6ounyMp0kQLRi2LhPHNxT7DLPQg5zyYGO1nV32YHHSxPN8aeA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793207961; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: In-Reply-To:References:User-Agent:X-stable:X-Patchwork-Hint: MIME-Version:Content-Transfer-Encoding; bh=BatabeKitl+1oE+zB+VVDzYQ/4auDl+s//Zb6zOfe6Y=; b=VIR7/uEpGzP4Y9ygVzSXNR4AzV2jkMgxMXcRxlgOmQF5skV6yZCcNofcVqa5yeFGH9ny uwlwsG8XJXHOw1aNpSSzAI+fmYVbQX4Y7BI9yvBWk4uQSwmlLWyxW6mQZ9+PgI0/XzO5F x+KHGbNWCP0yhDoMySaL8V98po2SIec5EnCDf8oixx6gFBHFgcq8pouoOhgRtDWZHIDp4 0bFb0MEz6riAARJYCwLx4k3HZD8Iojfk/U13vrKTCmyTY1I5vZ0JkwczAj8fNVT3iuyz3 3sLAs/nD09ORSIK4RnFQGAQVn8zw6WVmFMdhl2iYayG5r+eFXTy1ytNyWNfIOjb1wmg== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=q1k1NGVd; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D1576606A324; Wed, 28 Oct 2026 17:19:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.a=rsa-sha256 header.s=korg header.b=q1k1NGVd Received: by smtp.kernel.org (Postfix) with ESMTPSA id E22971F01825; Wed, 28 Oct 2026 17:19:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1793207960; bh=BatabeKitl+1oE+zB+VVDzYQ/4auDl+s//Zb6zOfe6Y=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=q1k1NGVddzC4XV8XqPpEOKUnW4khdeYnJTz1BdyLflggO9gPND3QeSpY+8IPGyt1O 0+2h4ZSbllXM8NQKpBQcMw9fS4aI2YZ4fFdkZQPlJQy5YFoJKVkp76rAnK++RIr/6Z Tma6Pf7ZhTkSwv2uG3bWIDK2ooY5AL+OvpWh/DFE= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Josef Bacik , Jens Axboe , "Claude Fable 5.1" Subject: [PATCH 6.12 200/247] io_uring/io-wq: dont exit with a creation pending Date: Wed, 28 Oct 2026 18:00:03 +0100 Message-ID: <20261028165952.155050337@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261028165947.349197979@linuxfoundation.org> References: <20261028165947.349197979@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore X-Mailing-List: patches@lists.linux.dev List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Josef Bacik Commit e231d2e8f80d3649ecd3851b7f2abdfbe606c04b upstream. A worker that is the last one to go to sleep while work is pending asks for another worker. io_wq_dec_running() bumps ->nr_running on behalf of the new worker and queues create_worker_cb() as task_work for the owner of the io-wq. Until that has run, everybody else takes it that a worker is running which is going to look after the work list: io_wq_enqueue() doesn't create one, and other workers that go to sleep don't find themselves to be the last. If the worker that made the request exits, io_worker_exit() cancels the task_work, and io_worker_cancel_cb() drops ->nr_running without a look at the work list: worker A worker B io_wq_enqueue() blocks, work is pending nr_running++ queues create_worker_cb() wakes, handles the work idle timeout, decides to exit picks up work 1 queues work 2 B is on the free list still: wakes B work 1 blocks nr_running 2 -> 1 io_worker_exit() io_worker_cancel_cb() nr_running 1 -> 0 Work 2 has to wait for work 1, although there is room for more workers. It takes an owner that doesn't get around to run its task_work for the time of the idle timeout, less if the worker exits because its affinity was changed or the io-wq is marked exit-on-idle. Let the worker stay around until its request has been dealt with. Only the worker itself sets ->create_state, so it can't be set behind its back once it has decided to leave. [ 6.12: no exit-on-idle state ] Fixes: 1d5f5ea7cb7d ("io-wq: remove worker to owner tw dependency") Assisted-by: LLM Signed-off-by: Josef Bacik Link: https://patch.msgid.link/20261015-b4-io-uring-fixes-v1-12-c1556f5d7bf5@toxicpanda.com Signed-off-by: Jens Axboe Co-Authored-By: Claude Fable 5.1 Signed-off-by: Greg Kroah-Hartman --- io_uring/io-wq.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) --- a/io_uring/io-wq.c +++ b/io_uring/io-wq.c @@ -708,8 +708,12 @@ static int io_wq_worker(void *data) /* * Last sleep timed out. Exit if we're not the last worker, * or if someone modified our affinity. + * Not as long as a request of ours for another worker is + * pending, though. It is accounted as a running worker, which + * others rely on, and io_worker_exit() would cancel it. */ - if (last_timeout && (exit_mask || acct->nr_workers > 1)) { + if (last_timeout && (exit_mask || acct->nr_workers > 1) && + !test_bit(0, &worker->create_state)) { acct->nr_workers--; if (test_and_clear_bit(IO_WORKER_F_FREE, &worker->flags)) hlist_nulls_del_init_rcu(&worker->nulls_node);