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 7AB5B4085D for ; Thu, 26 Sep 2024 20:21:32 +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=1727382092; cv=none; b=mJCGsZ7qDXIiWMQUQN+72XHi4evI5vL+Mg+K5NAApjb9q/dGiArXQHZNLOZkrvOsEuOs3fD1Kgs6EAxhlj+VcO0A8Ofw9uwuowy8SKaHaBg8pOyhytVY7flQIbINCO6Phyll09Hp4o6s18Yw+svlBTznmhV8jydcbuP0DCuYbV4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727382092; c=relaxed/simple; bh=PXh3wzvgTPSep8a82OzlPI3iEmG7z1vcYLsfrA4WbRA=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=AVABonx6vM4Q/sU3s7eKda6eXLPw3fpN+nTHo0VMgaPh2uL2SPvkn5+f4yiG/UQ0iAoPk4y0RICgu6vfFSPjvAzlasD6UvHJSx5oRXitY3V0rTAqKVsnnHbyOOrKsvtbdiAfmBExcJudccgc6RZp1aa/bba39XmrjMFA/pP3VJ0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=Ys3MuEQq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="Ys3MuEQq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 984BBC4CEC5; Thu, 26 Sep 2024 20:21:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1727382091; bh=PXh3wzvgTPSep8a82OzlPI3iEmG7z1vcYLsfrA4WbRA=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Ys3MuEQqRKez3P1oRPf+4kqDtVoVqwRjPxubw3pYYVS+JoHIcop9TEDWCqTgVNmME aajd/+7Xkjtjt5IaItPxQfVocPRumfAMIUtUmhBGWWKYVamxUYwVH46/i7DenpeHop ABx2o2KYIqsjb89d+i1vBTLt02sd93LqK542yew8= Date: Thu, 26 Sep 2024 13:21:30 -0700 From: Andrew Morton To: Frederic Weisbecker Cc: Thomas Gleixner , LKML , Hillf Danton , Tejun Heo , syzbot+943d34fa3cf2191e3068@syzkaller.appspotmail.com Subject: Re: [PATCH] kthread: Unpark only parked kthread Message-Id: <20240926132130.b1d1f6943d225368d3062d5e@linux-foundation.org> In-Reply-To: <20240913214634.12557-1-frederic@kernel.org> References: <20240913214634.12557-1-frederic@kernel.org> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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=US-ASCII Content-Transfer-Encoding: 7bit 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? 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?