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jc1obe4RrF85EGKvVD_WUGduUkKFvtcv X-Proofpoint-ORIG-GUID: jc1obe4RrF85EGKvVD_WUGduUkKFvtcv Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello Tejun, On 16/8/22 9:27 am, Tejun Heo wrote: > Bringing up a CPU may involve creating new tasks which requires read-locking > threadgroup_rwsem, so threadgroup_rwsem nests inside cpus_read_lock(). > However, cpuset's ->attach(), which may be called with thredagroup_rwsem > write-locked, also wants to disable CPU hotplug and acquires > cpus_read_lock(), leading to a deadlock. > > Fix it by guaranteeing that ->attach() is always called with CPU hotplug > disabled and removing cpus_read_lock() call from cpuset_attach(). > > Signed-off-by: Tejun Heo > --- > Hello, sorry about the delay. > > So, the previous patch + the revert isn't quite correct because we sometimes > elide both cpus_read_lock() and threadgroup_rwsem together and > cpuset_attach() woudl end up running without CPU hotplug enabled. Can you > please test whether this patch fixes the problem? > This fixes the issue seen in my setup. As my setup is 5.4 based I used cgroup_attach_lock/unlock(true) in the backport version of your patch. Feel free to add my Reviewed-and-tested-by: Imran Khan Thanks, -- Imran From mboxrd@z Thu Jan 1 00:00:00 1970 From: Imran Khan Subject: Re: [PATCH cgroup/for-6.0-fixes] cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock Date: Wed, 17 Aug 2022 06:20:08 +1000 Message-ID: References: <224b19f3-912d-b858-7af4-185b8e55bc66@quicinc.com> <20220815090556.GB27407@blackbody.suse.cz> <20220815093934.GA29323@blackbody.suse.cz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=message-id : date : subject : to : cc : references : from : in-reply-to : content-type : content-transfer-encoding : mime-version; s=corp-2022-7-12; bh=+Gnw3FoslHgHWTQOPkfA4s6HrAjZORX0MGRQTTSLwx8=; b=U0suUQnmxWJskUAtWRliCSNEXoeo8SIdxHDbT2JaZMVtNe/W7IMYOLo/fTjTJctymDrN ZQkxyZ/Wvaea9ANct/Q6G1Xssm/yCLkJCwetT97uBihjgF5+K/LDvHUKRr5HC8UzufFC 2RT5YVp3fb2rT8BD3klmLOBfXKoR02YLgOiKRr8syKvQxTVYnysPJYVEN8d8odNDJtzC uP7iTPxuqicySj22CkbmaM339A9G5ZwoYBLl4BrAc2VOoS62wR9r2RRG8kuo49NpcJRp 8RJEJBcNWG75ESe1AQmt/ugVdFjqQRB0DtbvakMYUvV433+9gQDHxvE7TrpCF/R7lwad lw== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.onmicrosoft.com; s=selector2-oracle-onmicrosoft-com; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=+Gnw3FoslHgHWTQOPkfA4s6HrAjZORX0MGRQTTSLwx8=; b=prGZ++SOKfkz6mOzQdaXeZUipZsSgM9AjqJAiBSupe2b+z383wWIytvQkepMT+d5vNplUlFtQqlUuvqvcqcWjO/10ExchlhAzxeqfuF8UdrsIypvmo8f16/Z7sLfNCq811sgWmTuy8nreHFw3xmAY34kP7JRKY2wn3QQVPjNQLc= Content-Language: en-US In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii" To: Tejun Heo , Mukesh Ojha Cc: =?UTF-8?Q?Michal_Koutn=c3=bd?= , Xuewen Yan , lizefan.x-EC8Uxl6Npydl57MIdRCFDg@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, tglx-hfZtesqFncYOwBW4kG4KsQ@public.gmane.org, steven.price-5wv7dgnIgG8@public.gmane.org, peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Zhao Gongyi , Zhang Qiao Hello Tejun, On 16/8/22 9:27 am, Tejun Heo wrote: > Bringing up a CPU may involve creating new tasks which requires read-locking > threadgroup_rwsem, so threadgroup_rwsem nests inside cpus_read_lock(). > However, cpuset's ->attach(), which may be called with thredagroup_rwsem > write-locked, also wants to disable CPU hotplug and acquires > cpus_read_lock(), leading to a deadlock. > > Fix it by guaranteeing that ->attach() is always called with CPU hotplug > disabled and removing cpus_read_lock() call from cpuset_attach(). > > Signed-off-by: Tejun Heo > --- > Hello, sorry about the delay. > > So, the previous patch + the revert isn't quite correct because we sometimes > elide both cpus_read_lock() and threadgroup_rwsem together and > cpuset_attach() woudl end up running without CPU hotplug enabled. Can you > please test whether this patch fixes the problem? > This fixes the issue seen in my setup. As my setup is 5.4 based I used cgroup_attach_lock/unlock(true) in the backport version of your patch. Feel free to add my Reviewed-and-tested-by: Imran Khan Thanks, -- Imran