From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7F4E71D0434 for ; Wed, 2 Oct 2024 14:15:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727878508; cv=none; b=Q8BiF13mk4EHFVdbf0aq9RFQYtdn0cdXLqH6EcooLRDz8FSBIWMB5OiTKAlUnLKxXQ8kkg10LVru6KcT5T5xde1eWVFmpthgs4AXOfSV8to/XeVa72sTc7dsWZLfG/XyB1sbT3GPlpldruim1afber7w8/TIP7NxUua1O4HBeTk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727878508; c=relaxed/simple; bh=5c6CzrRmIZzi6AssPCOjh+tRfUfHUxh80sJSkK9Dm0Y=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Ta6NSUWQQHpN1gxTb4KTBRHx0+stZU1PMhkrQDMkmtz44GlOeKRDHKYg81giZ0GU/aMxmf+1GLfNBy0tjavrdy+p0S96V+vDW8fYiT7nfPkSBFj2LQ7P+2CUJhfQnJN104sruUaNr8981VQMW0kEml1v2LOGx4psoFv35qKhM1U= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YUNZH1iQ; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YUNZH1iQ" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B7D0EC4CEC2; Wed, 2 Oct 2024 14:15:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1727878508; bh=5c6CzrRmIZzi6AssPCOjh+tRfUfHUxh80sJSkK9Dm0Y=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=YUNZH1iQFWUOdXn7vk27Nqf8FxVEy+lciqd/J4aOKW2Wemcu2mwWhvQO55UUqFJi2 mtLWmtTiDSnZzs/GHJplskRe4DQ8uJn9YZG4GTpdbPpXyuwhj72I2RjUF66iA6RexG XDvSgKsl5nEgvtzqOpGklVvMFEkT3dQH0ca89gBCeAl54CEKWpWPtFbkbNPsomAL0j 0snSwPWn+7SzTLmmgmpx5rV98GdVjE9+FARXhrR79nz9AdSRdFueTmaac7e/GN80KX 5E+T1QTugpqwQ1AhljV3554LzfLoQ40bYACQ+sshCoCF9EtDR+7QZdwVbpCkV2QLpC 6qUlqrDwIBpVg== Date: Wed, 2 Oct 2024 16:15:05 +0200 From: Frederic Weisbecker To: Andrew Morton Cc: Thomas Gleixner , LKML , Hillf Danton , Tejun Heo , syzbot+943d34fa3cf2191e3068@syzkaller.appspotmail.com Subject: Re: [PATCH] kthread: Unpark only parked kthread Message-ID: References: <20240913214634.12557-1-frederic@kernel.org> <20240926132130.b1d1f6943d225368d3062d5e@linux-foundation.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240926132130.b1d1f6943d225368d3062d5e@linux-foundation.org> Le Thu, Sep 26, 2024 at 01:21:30PM -0700, Andrew Morton a écrit : > On Fri, 13 Sep 2024 23:46:34 +0200 Frederic Weisbecker wrote: > > > Calling into kthread unparking unconditionally is mostly harmless when > > the kthread is already unparked. The wake up is then simply ignored > > because the target is not in TASK_PARKED state. > > > > However if the kthread is per CPU, the wake up is preceded by a call > > to kthread_bind() which expects the task to be inactive and in > > TASK_PARKED state, which obviously isn't the case if it is unparked. > > > > As a result, calling kthread_stop() on an unparked per-cpu kthread > > triggers such a warning: > > > > WARNING: CPU: 0 PID: 11 at kernel/kthread.c:525 __kthread_bind_mask kernel/kthread.c:525 > > > > kthread_stop+0x17a/0x630 kernel/kthread.c:707 > > destroy_workqueue+0x136/0xc40 kernel/workqueue.c:5810 > > wg_destruct+0x1e2/0x2e0 drivers/net/wireguard/device.c:257 > > netdev_run_todo+0xe1a/0x1000 net/core/dev.c:10693 > > default_device_exit_batch+0xa14/0xa90 net/core/dev.c:11769 > > ops_exit_list net/core/net_namespace.c:178 [inline] > > cleanup_net+0x89d/0xcc0 net/core/net_namespace.c:640 > > process_one_work kernel/workqueue.c:3231 [inline] > > process_scheduled_works+0xa2c/0x1830 kernel/workqueue.c:3312 > > worker_thread+0x86d/0xd70 kernel/workqueue.c:3393 > > kthread+0x2f0/0x390 kernel/kthread.c:389 > > ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147 > > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244 > > > > > > Fix this with skipping unecessary unparking while stopping a kthread. > > How does userspace trigger this? Is it an issue in current mainline? I guess it takes some module unload performing a destroy workqueue to trigger this. And it's an issue in current mainline. > > Should we backport the fix into -stable kernels (depends on the answers > to the above questions). > > It looks like the issue is old, so a Fixes: probably isn't needed. But > as the issue is old, why did it come to light now? It's hard to tell. The core of the issue is there for a long while but the conditions for it to really happen in practice is probably since: 5c25b5ff89f0 (workqueue: Tag bound workers with KTHREAD_IS_PER_CPU) So it might deserve a Fixes: actually. Thanks.