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[2603:800c:1a02:1bae:e24f:43ff:fee6:449f]) by smtp.gmail.com with ESMTPSA id e20sm1545621pfv.59.2021.10.19.10.45.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 19 Oct 2021 10:45:59 -0700 (PDT) Sender: Tejun Heo Date: Tue, 19 Oct 2021 07:45:57 -1000 From: Tejun Heo To: Youfu Zhang Cc: axboe@kernel.dk, cgroups@vger.kernel.org, linux-block@vger.kernel.org Subject: Re: [BUG] blk-throttle panic on 32bit machine after startup Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Oct 18, 2021 at 03:08:53PM +0800, Youfu Zhang wrote: > Hi, > > I ran into a kernel bug related to blk-throttle on CentOS 7 AltArch for i386. > Userspace programs may panic the kernel if they hit the I/O limit > within 5 minutes after startup. > > Root cause: > 1. jiffies was initialized to -300HZ during boot on 32bit machines > 2. enable blkio cgroup hierarchy > __DEVEL__sane_behavior for cgroup v1 or default hierarchy for cgroup v2 > EL7 kernel modified throtl_pd_init and always enable hierarchical throttling > 3. enable & trigger blkio throttling within 5 minutes after startup > bio propagated from child tg to parent > 4. enter throtl_start_new_slice_with_credit > if(time_after_eq(start, tg->slice_start[rw])) > aka. time_after_eq(0xFFFxxxxx, 0) does not hold > parent tg->slice_start[rw] was zero-initialized and not updated > 5. enter throtl_trim_slice > BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw])) > aka. time_before(0xFFFxxxxx, 0) triggers a panic This doesn't reproduce on 5.14. Thanks. -- tejun From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tejun Heo Subject: Re: [BUG] blk-throttle panic on 32bit machine after startup Date: Tue, 19 Oct 2021 07:45:57 -1000 Message-ID: References: Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=2MlySN5JbrqzxF/Em4ggjCL2GMkbXRbHLm4CFSB5M5I=; b=cNd6/BHJIRYcPDuXiiaGgGr4U3V9uE4qNprUYOv81pfog4kXAogbLT8Soi9Q5nMjyA 3sEnP7x22YmWxIbl8dgVaHcT+99BrRLMrQQ/wd/FfiH9Q8WmGCHjq9q8esWhid5E7hws 0SYmG/UVbn6H0J3YGQbXmWNCCCzOBnS0E3BN4du6DdvRVx5uW52BwLuGUW5c/Z8DDqvp IFrCKb/2BW9EYdF0EiiXz+xY63OC1DFoKna6vLrCaoOMO3HjUxWbh+K8DpRV235S7Bca tata+q2H+0kz2Lo9xTopCiziDO4CGZLfX1hzmLPCr1y/P+MTxnLcr8H0XyWp9axC7LOP 1cNA== Sender: Tejun Heo Content-Disposition: inline In-Reply-To: List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Youfu Zhang Cc: axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-block-u79uwXL29TY76Z2rM5mHXA@public.gmane.org On Mon, Oct 18, 2021 at 03:08:53PM +0800, Youfu Zhang wrote: > Hi, > > I ran into a kernel bug related to blk-throttle on CentOS 7 AltArch for i386. > Userspace programs may panic the kernel if they hit the I/O limit > within 5 minutes after startup. > > Root cause: > 1. jiffies was initialized to -300HZ during boot on 32bit machines > 2. enable blkio cgroup hierarchy > __DEVEL__sane_behavior for cgroup v1 or default hierarchy for cgroup v2 > EL7 kernel modified throtl_pd_init and always enable hierarchical throttling > 3. enable & trigger blkio throttling within 5 minutes after startup > bio propagated from child tg to parent > 4. enter throtl_start_new_slice_with_credit > if(time_after_eq(start, tg->slice_start[rw])) > aka. time_after_eq(0xFFFxxxxx, 0) does not hold > parent tg->slice_start[rw] was zero-initialized and not updated > 5. enter throtl_trim_slice > BUG_ON(time_before(tg->slice_end[rw], tg->slice_start[rw])) > aka. time_before(0xFFFxxxxx, 0) triggers a panic This doesn't reproduce on 5.14. Thanks. -- tejun