From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mta-65-228.siemens.flowmailer.net (mta-65-228.siemens.flowmailer.net [185.136.65.228]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 77B311C86F2 for ; Fri, 6 Sep 2024 13:54:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.136.65.228 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725630902; cv=none; b=K+mRQEJpeVo2W1zW8cnf9rqNaPihmbuejgciXP9dGvBTOW4UpnPiyH8/8tohcPEJBLIj2htaIMlAEw/5g4qHzM10USrzOVx3Lx8eqo5zMAf/nWLBc1QtAAUgcY1/NUX6xILUB1tFC2ioyraLJol2g1x78eqKU8nH3MO9GeaE0jw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1725630902; c=relaxed/simple; bh=xs4PM9vkPSMYbTYGO+9bC9fPgWgnXTJnnUe/1utVaUQ=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=XhWhtALPRMDcE83m7udhJHe+Ja5Tz6vsLs/ARds9z5FxKzIHYPOzArX/UzYaZvntJkL0Nvd+v9AXpW1Rcpp1msmS9FSTTNzCwMmRLECz7G367Vu3HnRMRgqceMs88ZELxBtKvUtjvu/xnCgcr07VDcJB0XGMaK6r4Ml3paAV2Z8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=siemens.com; spf=pass smtp.mailfrom=rts-flowmailer.siemens.com; dkim=pass (2048-bit key) header.d=siemens.com header.i=felix.moessbauer@siemens.com header.b=Ijr6whoC; arc=none smtp.client-ip=185.136.65.228 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=siemens.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rts-flowmailer.siemens.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=siemens.com header.i=felix.moessbauer@siemens.com header.b="Ijr6whoC" Received: by mta-65-228.siemens.flowmailer.net with ESMTPSA id 2024090613444582c1367185f93f261c for ; Fri, 06 Sep 2024 15:44:46 +0200 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; s=fm1; d=siemens.com; i=felix.moessbauer@siemens.com; h=Date:From:Subject:To:Message-ID:MIME-Version:Content-Type:Content-Transfer-Encoding:Cc; bh=BbquwJ4rJZoL/N4IYBuwdhGe1dp/yVc4+3fJ/LgtoaI=; b=Ijr6whoC0shvNVFPpfYZ9jo71J6ULVMe6KHeqU8dW0ZTVJ2taRQ+YF4Uj2z5fwjBBAw6td PL3iu1kvl+hWj5tbRaDwHMsW+pZWy4H6E394AiPM3kQb5WEIAyqZX6WMQ9MfxpWPCuiZARwN tlYphoMrr2bsHV/tjZt2HhwFfT3H2qSamjg+GZ+V3FpaOiQ7OYKdCO2LusidLU6mO/kbKHsF cHi3oAQScvL7acoQEh4RjCO34D2kzyC+rBn03vAKiP+O03SuOfT6zRk4A0AEbKjM9DpwureI UZdNsYVb82ZlhPi7tXNLIgPtOlk8wxBsQ4TqzoWHaSA3oPzTzIUlvZ3w==; From: Felix Moessbauer To: axboe@kernel.dk, asml.silence@gmail.com Cc: linux-kernel@vger.kernel.org, io-uring@vger.kernel.org, cgroups@vger.kernel.org, dqminh@cloudflare.com, longman@redhat.com, adriaan.schmidt@siemens.com, florian.bezdeka@siemens.com, Felix Moessbauer , stable@vger.kernel.org Subject: [PATCH 1/1] io_uring/sqpoll: inherit cpumask of creating process Date: Fri, 6 Sep 2024 15:44:33 +0200 Message-Id: <20240906134433.433083-1-felix.moessbauer@siemens.com> Precedence: bulk X-Mailing-List: io-uring@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Flowmailer-Platform: Siemens Feedback-ID: 519:519-1321639:519-21489:flowmailer The submit queue polling threads are "kernel" threads that are started from the userland. In case the userland task is part of a cgroup with the cpuset controller enabled, the poller should also stay within that cpuset. This also holds, as the poller belongs to the same cgroup as the task that started it. With the current implementation, a process can "break out" of the defined cpuset by creating sq pollers consuming CPU time on other CPUs, which is especially problematic for realtime applications. Part of this problem was fixed in a5fc1441 by dropping the PF_NO_SETAFFINITY flag, but this only becomes effective after the first modification of the cpuset (i.e. the pollers cpuset is correct after the first update of the enclosing cgroups cpuset). By inheriting the cpuset of the creating tasks, we ensure that the poller is created with a cpumask that is a subset of the cgroups mask. Inheriting the creators cpumask is reasonable, as other userland tasks also inherit the mask. Fixes: 37d1e2e3642e ("io_uring: move SQPOLL thread io-wq forked worker") Cc: stable@vger.kernel.org # 6.1+ Signed-off-by: Felix Moessbauer --- io_uring/sqpoll.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/io_uring/sqpoll.c b/io_uring/sqpoll.c index 3b50dc9586d1..4681b2c41a96 100644 --- a/io_uring/sqpoll.c +++ b/io_uring/sqpoll.c @@ -289,7 +289,7 @@ static int io_sq_thread(void *data) if (sqd->sq_cpu != -1) { set_cpus_allowed_ptr(current, cpumask_of(sqd->sq_cpu)); } else { - set_cpus_allowed_ptr(current, cpu_online_mask); + set_cpus_allowed_ptr(current, sqd->thread->cpus_ptr); sqd->sq_cpu = raw_smp_processor_id(); } -- 2.39.2