From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753228AbdEIPEY (ORCPT ); Tue, 9 May 2017 11:04:24 -0400 Received: from mout.gmx.net ([212.227.17.20]:56588 "EHLO mout.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751304AbdEIPEX (ORCPT ); Tue, 9 May 2017 11:04:23 -0400 Message-ID: <1494342256.4440.3.camel@gmx.de> Subject: Re: get/put_cpu() usage in block/blk-mq.c From: Mike Galbraith To: Jens Axboe Cc: LKML Date: Tue, 09 May 2017 17:04:16 +0200 In-Reply-To: References: <1494310029.20252.44.camel@gmx.de> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Provags-ID: V03:K0:h8ev3+/ugWoR5vS2VwESzukZ6Qc1+5yTeGLSXMXNzcNnPtehs/k B4Ymq8nz1UjeWrNnCSOoYyD8lkP8UbFJ6OrsOa0R/8JCHggKt3ZDrXzOta8VS96oJCoI+WZ 47jqnQ4bh6LzTQI238qrXbBiJKeKrcRXdfUdSWfHgume2Pl8ZiC44IakGlolta2YbUANtPm hg8sDi4OJpEgGiTONOMMQ== X-UI-Out-Filterresults: notjunk:1;V01:K0:ZnH9k8GFsv4=:huaxG6w+PP8jOUN0QouwSt lvp74w5MwJH2EHV2YzKzkT1N4GquMSvGM9hDMW/zzE1W5sV8jGtMzm4a3rQYTiKYAndwUhS5C FqtdkMflk3AQMGi72MlFBLUM8v1HIhGLEZIEpF1SIeA4Lr32DYFaLUR8nTfF2UQCmkdIDV3ra vsKfUDXRztMykgoAqGoweJcsyeDD8fK1HR1vHnJkRDkpMQdwKbINvZ6nc+MIT5JH/DFhXAb74 ljyoEaycLHCxhee415gi1fV96Jg/rKesfMlpzdIjbJJV2UQdZQUDnX9OEh8x+AZjm8LwLL5+W jPvia2sNWK4prjyFTCJzimde//BtgSyHjUT9O2v12ZCV+75v+A/HRYcP3oaS9PPKQw6XsneDW ytHAHIP5ZK2hnoS1lNXdr38/+ct8xLTf/2VDd76rx4GtHNRAP+XdhR8+JjmjnOFaSEjrAZDBJ x+oOKxuF5HCFIVNcKkL4gluqAabvaAXmzI0U9h7+cTDwFjkJqRazJsGGK4NV62GSL+zw60zT5 Daf8oEtidosMcGYo/IaFqHWTzFS8Wnf0xZxkzjgdHccU0KzE6ns8f9BDHDxvYmz9FpVRyaGX6 spzxFDvneQxKdQHxy2TVhNaOD2pIl3BRX04QqrlbNTRukhifKbEK7+HgrTDAlQruv2cDRCZDY z7CDzNptem6O6gCLMc/djUIOdvgaKNXSXahXcP9ygF827ltCfYz4HAIamE6tiVeLKWMFg6rv8 9rqMQ8FjaK0jk9PfnO+KPojC6PfBtTIefXai0PfCkDkBA/apcMA0dZjdTBvhj/xpGRBR03JMj RzjiCI7 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2017-05-09 at 08:53 -0600, Jens Axboe wrote: > On 05/09/2017 12:07 AM, Mike Galbraith wrote: > > Hi Jens, > > > > I was about to fix up this splat.. > > > > [ 445.022141] loop: module loaded > > [ 445.078116] BUG: using smp_processor_id() in preemptible [00000000] code: loop0/3801 > > [ 445.085873] caller is debug_smp_processor_id+0x17/0x20 > > [ 445.091016] CPU: 7 PID: 3801 Comm: loop0 Tainted: G E 4.12.0-default #40 > > [ 445.098838] Hardware name: IBM System x3550 M3 -[7944K3G]-/69Y5698 , BIOS -[D6E150AUS-1.10]- 12/15/2010 > > [ 445.108564] Call Trace: > > [ 445.111016] dump_stack+0x65/0x89 > > [ 445.114330] check_preemption_disabled+0xde/0xf0 > > [ 445.118945] debug_smp_processor_id+0x17/0x20 > > [ 445.123300] blk_stat_add+0xb0/0x130 > > [ 445.126876] __blk_mq_complete_request+0xb5/0x150 > > [ 445.131575] blk_mq_complete_request+0x16/0x20 > > [ 445.136020] loop_queue_work+0x5f/0xaa0 [loop] > > [ 445.140461] ? _raw_spin_unlock_irq+0x21/0x40 > > [ 445.144816] ? finish_task_switch+0x85/0x270 > > [ 445.149085] ? __schedule+0x291/0x8c0 > > [ 445.152747] kthread_worker_fn+0xc2/0x1d0 > > [ 445.156754] kthread+0x114/0x150 > > [ 445.159983] ? __kthread_init_worker+0xb0/0xb0 > > [ 445.164424] ? kthread_park+0x60/0x60 > > [ 445.168085] ret_from_fork+0x2c/0x40 > > Is it from this_cpu_ptr() in blk_stat_add()? Yeah. > > ..but then noticed that __blk_mq_run_hw_queue() is also called under > > get_cpu(), but recently grew a might_sleep(), so maybe wants some block > > layer eyeballs. > > That part is fine. The might sleep depends on BLOCKING being set in > the hardware queue flags. And if that is set, then we don't call > it under get_cpu(). Ah, right. -Mike