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[23.128.96.18]) by mx.google.com with ESMTP id d10si1665816edu.542.2020.11.11.07.03.39; Wed, 11 Nov 2020 07:04:06 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=pass header.i=@linaro.org header.s=google header.b=RmKRnEeu; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727215AbgKKPBr (ORCPT + 99 others); Wed, 11 Nov 2020 10:01:47 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726204AbgKKPBq (ORCPT ); Wed, 11 Nov 2020 10:01:46 -0500 Received: from mail-lj1-x242.google.com (mail-lj1-x242.google.com [IPv6:2a00:1450:4864:20::242]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42153C0613D1 for ; Wed, 11 Nov 2020 07:01:46 -0800 (PST) Received: by mail-lj1-x242.google.com with SMTP id s9so2404535ljo.11 for ; Wed, 11 Nov 2020 07:01:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=cBLmYkGf36dydiwFqnzHp6MitrhQHxL3O/6ldq0sG2I=; b=RmKRnEeuCL1nM5d9rx9eFQwWoH8ZYxDGI3/Kz40AbjtrdAGQIzj1oqk8IpiQ0fy4u3 o5ZtCwdubmUjx7kw08Y054oXSxu7zgz3IDzu6XD01n0UhLnqWquZOFzbnLxRfLKFO5Zr QXdKFeSwudeH9koiU8jw1Tr+t1RN1XTs0Ddsrm/QR1UGZ6kvNs3dXugNqts91326eBOE 6fkaJ3Sn1K1m+6yLwQR9tOrd+iInFOFCOMUBdbAjGczbFgiAqjaA5sAS4P6afQw9jTET dFiDxlbx4d805mTL8aPaX49Uj5NrLyaliiHKHATc8rZHEsVzFPuHK0urEPWtG0gR+0Kc l3OA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=cBLmYkGf36dydiwFqnzHp6MitrhQHxL3O/6ldq0sG2I=; b=rTSAsdI1/zYx1BPre8MBMKV6IBWkqG9tQwtJDUQZej+XwCzs1Vndvqk+6ghkp3kSyZ AXGQCRwJuzwk6my5rVendUNPjRgzmX8J3ej9QcJ6mJs0hfgZ8glcw9R7bB04MifwB3pE w+LkenPtKosG0kvCaQLL4NANp3YaU4WqaerHUaiV+O/Eo3f9pOgjKt4HFVenlCF5K2Zd uXa6gt1VMcJlRyDnAgj8jedWM4vxGtZY2tuK1fIjVqQN0ZfWyux39azeLbmGKwogs8oe 9Y/uTj0WRkPNqsEqmJ5T26io8Lf4llw0ckFH50Tva/xxnetpMofnUrvlaGPbwaVwNFDN wnWg== X-Gm-Message-State: AOAM53042qrw55J/7kD9VpKgI9dLX4fR1sqccEauRreJXykUIHD9hdDx gPDa/MQhs+WRad3rcGqyMI9fe1pvCSojpvoGtpQd5Q== X-Received: by 2002:a2e:5450:: with SMTP id y16mr11307487ljd.288.1605106904415; Wed, 11 Nov 2020 07:01:44 -0800 (PST) MIME-Version: 1.0 References: <20201110135320.3309507-1-elver@google.com> In-Reply-To: From: Anders Roxell Date: Wed, 11 Nov 2020 16:01:33 +0100 Message-ID: Subject: Re: [PATCH] kfence: Avoid stalling work queue task without allocations To: Marco Elver Cc: Andrew Morton , Alexander Potapenko , Dmitry Vyukov , Jann Horn , Mark Rutland , Linux Kernel Mailing List , Linux-MM , kasan-dev Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 11 Nov 2020 at 09:29, Marco Elver wrote: > > On Wed, 11 Nov 2020 at 00:23, Anders Roxell wrote: > [...] > > > > I gave them a spin on next-20201105 [1] and on next-20201110 [2]. > > > > I eventually got to a prompt on next-20201105. > > However, I got to this kernel panic on the next-20201110: > > > > [...] > > [ 1514.089966][ T1] Testing event system initcall: OK > > [ 1514.806232][ T1] Running tests on all trace events: > > [ 1514.857835][ T1] Testing all events: > > [ 1525.503262][ C0] hrtimer: interrupt took 10902600 ns > > [ 1623.861452][ C0] BUG: workqueue lockup - pool cpus=0 node=0 > > flags=0x0 nice=0 stuck for 65s! > > [...] > > [ 7823.104349][ T28] Tainted: G W > > 5.10.0-rc3-next-20201110-00008-g8dc06700529d #3 > > [ 7833.206491][ T28] "echo 0 > > > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > [ 7840.750700][ T28] task:kworker/0:1 state:D stack:26640 pid: > > 1872 ppid: 2 flags:0x00000428 > > [ 7875.642531][ T28] Workqueue: events toggle_allocation_gate > > [ 7889.178334][ T28] Call trace: > > [ 7897.066649][ T28] __switch_to+0x1cc/0x1e0 > > [ 7905.326856][ T28] 0xffff00000f7077b0 > > [ 7928.354644][ T28] INFO: lockdep is turned off. > > [ 7934.022572][ T28] Kernel panic - not syncing: hung_task: blocked tasks > > [ 7934.032039][ T28] CPU: 0 PID: 28 Comm: khungtaskd Tainted: G > > W 5.10.0-rc3-next-20201110-00008-g8dc06700529d #3 > > [ 7934.045586][ T28] Hardware name: linux,dummy-virt (DT) > > [ 7934.053677][ T28] Call trace: > > [ 7934.060276][ T28] dump_backtrace+0x0/0x420 > > [ 7934.067635][ T28] show_stack+0x38/0xa0 > > [ 7934.091277][ T28] dump_stack+0x1d4/0x278 > > [ 7934.098878][ T28] panic+0x304/0x5d8 > > [ 7934.114923][ T28] check_hung_uninterruptible_tasks+0x5e4/0x640 > > [ 7934.123823][ T28] watchdog+0x138/0x160 > > [ 7934.131561][ T28] kthread+0x23c/0x260 > > [ 7934.138590][ T28] ret_from_fork+0x10/0x18 > > [ 7934.146631][ T28] Kernel Offset: disabled > > [ 7934.153749][ T28] CPU features: 0x0240002,20002004 > > [ 7934.161476][ T28] Memory Limit: none > > [ 7934.171272][ T28] ---[ end Kernel panic - not syncing: hung_task: > > blocked tasks ]--- > > > > Cheers, > > Anders > > [1] https://people.linaro.org/~anders.roxell/output-next-20201105-test.log > > [2] https://people.linaro.org/~anders.roxell/output-next-20201110-test.log > > Thanks for testing. The fact that it passes on next-20201105 but not > on 20201110 is strange. If you boot with KFENCE disabled (boot param > kfence.sample_interval=0), does it boot? This is my qemu cmdline with kfence.sample_interval=0 $ qemu-system-aarch64 --enable-kvm -cpu cortex-a53 -kernel Image-20201110-test -serial stdio -monitor none -nographic -m 2G -M virt -fsdev local,id=root,path=/srv/kvm/tmp/stretch/arm64-test,security_model=none,writeout=immediate -device virtio-rng-pci -device virtio-9p-pci,fsdev=root,mount_tag=/dev/root -append "root=/dev/root rootfstype=9p rootflags=trans=virtio console=ttyAMA0,38400n8 earlycon=pl011,0x9000000 initcall_debug softlockup_panic=0 security=none kpti=no kfence.sample_interval=0" This is the result, I managed to get to the prompt. see https://people.linaro.org/~anders.roxell/output-next-20201110-test-2.log Cheers, Anders > > In your log [2] I see a number of "BUG: workqueue lockup ..." but that > doesn't make sense, at least I don't think the KFENCE work item is > causing this. It'd be interesting to bisect what changed between > 20201105 and 20201110, but I have a suspicion that might take too > long. Short of that, let me see if there are any changes between the 2 > that look like it might be causing this. > > Thanks, > -- Marco