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Sat, 14 Apr 2018 15:54:17 -0400 Received: from mail-pf0-f196.google.com ([209.85.192.196]:42743 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751684AbeDNTyQ (ORCPT ); Sat, 14 Apr 2018 15:54:16 -0400 X-Google-Smtp-Source: AIpwx49xOEVPnlctykXjV1CZnV9vrq5gOpDVUqeBbibUY8bgbeyLm/RYZ2p4xvYksiIeUnKNL26Z2Q== Subject: Re: [PATCH v2] block: do not use interruptible wait anywhere To: Alan Jenkins , linux-block@vger.kernel.org Cc: Bart Van Assche , linux-kernel@vger.kernel.org, stable@vger.kernel.org References: <13e67e1243ebd96f3f56a150d47444ada47ebde0.camel@wdc.com> <20180412181158.8884-1-alan.christopher.jenkins@gmail.com> From: Jens Axboe Message-ID: <9111da3e-1b16-3e73-fa3a-940f5a43c545@kernel.dk> Date: Sat, 14 Apr 2018 13:54:12 -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: <20180412181158.8884-1-alan.christopher.jenkins@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: On 4/12/18 12:11 PM, Alan Jenkins wrote: > When blk_queue_enter() waits for a queue to unfreeze, or unset the > PREEMPT_ONLY flag, do not allow it to be interrupted by a signal. > > The PREEMPT_ONLY flag was introduced later in commit 3a0a529971ec > ("block, scsi: Make SCSI quiesce and resume work reliably"). Note the SCSI > device is resumed asynchronously, i.e. after un-freezing userspace tasks. > > So that commit exposed the bug as a regression in v4.15. A mysterious > SIGBUS (or -EIO) sometimes happened during the time the device was being > resumed. Most frequently, there was no kernel log message, and we saw Xorg > or Xwayland killed by SIGBUS.[1] > > [1] E.g. https://bugzilla.redhat.com/show_bug.cgi?id=1553979 > > Without this fix, I get an IO error in this test: > > # dd if=/dev/sda of=/dev/null iflag=direct & \ > while killall -SIGUSR1 dd; do sleep 0.1; done & \ > echo mem > /sys/power/state ; \ > sleep 5; killall dd # stop after 5 seconds > > The interruptible wait was added to blk_queue_enter in > commit 3ef28e83ab15 ("block: generic request_queue reference counting"). > Before then, the interruptible wait was only in blk-mq, but I don't think > it could ever have been correct. Applied, thanks. Still want that test in blktests, though! -- Jens Axboe