From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759457AbeD1AxF (ORCPT ); Fri, 27 Apr 2018 20:53:05 -0400 Received: from mail-pf0-f195.google.com ([209.85.192.195]:42238 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755617AbeD1AxD (ORCPT ); Fri, 27 Apr 2018 20:53:03 -0400 X-Google-Smtp-Source: AB8JxZouGcfH9f3LE1zdVraeTiOjdrkBBTpgoBsGCDsqcjfRM2jQSbVLcrE3QAdbB43ZiJUJDeOsHQ== Subject: Re: ed74ae0342 ("blk-mq: Avoid that a completion can be ignored .."): BUG: kernel hang in test stage To: kernel test robot , Bart Van Assche Cc: LKP , linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, wfg@linux.intel.com References: <5adf9ada.EgNO094GdvSdHQ3v%lkp@intel.com> From: Jens Axboe Message-ID: <07256b82-12b1-9ccf-c660-9dfbedfd3cac@kernel.dk> Date: Fri, 27 Apr 2018 18:52:58 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 MIME-Version: 1.0 In-Reply-To: <5adf9ada.EgNO094GdvSdHQ3v%lkp@intel.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/24/18 3:00 PM, kernel test robot wrote: > Greetings, > > 0day kernel testing robot got the below dmesg and the first bad commit is > > https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux-block.git for-linus > > commit ed74ae03424684a6ad8a973c3fa727c6b4162432 > Author: Bart Van Assche > AuthorDate: Thu Apr 19 09:43:53 2018 -0700 > Commit: Jens Axboe > CommitDate: Thu Apr 19 14:21:47 2018 -0600 > > blk-mq: Avoid that a completion can be ignored for BLK_EH_RESET_TIMER > > The blk-mq timeout handling code ignores completions that occur after > blk_mq_check_expired() has been called and before blk_mq_rq_timed_out() > has reset rq->aborted_gstate. If a block driver timeout handler always > returns BLK_EH_RESET_TIMER then the result will be that the request > never terminates. > > Fix this race as follows: > - Use the deadline instead of the request generation to detect whether > or not a request timer fired after reinitialization of a request. > - Store the request state in the lowest two bits of the deadline instead > of the lowest two bits of 'gstate'. > - Rename MQ_RQ_STATE_MASK into RQ_STATE_MASK and change it from an > enumeration member into a #define such that its type can be changed > into unsigned long. That allows to write & ~RQ_STATE_MASK instead of > ~(unsigned long)RQ_STATE_MASK. > - Remove all request member variables that became superfluous due to > this change: gstate, gstate_seq and aborted_gstate_sync. > - Remove the request state information that became superfluous due to this > patch, namely RQF_MQ_TIMEOUT_EXPIRED. > - Remove the code that became superfluous due to this change, namely > the RCU lock and unlock statements in blk_mq_complete_request() and > also the synchronize_rcu() call in the timeout handler. Any chance you can try with the newer version? https://github.com/bvanassche/linux/commit/4acd555fa13087 -- Jens Axboe