Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757206AbcLUIp3 (ORCPT ); Wed, 21 Dec 2016 03:45:29 -0500 Received: from cn.fujitsu.com ([59.151.112.132]:64168 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1756244AbcLUIpW (ORCPT ); Wed, 21 Dec 2016 03:45:22 -0500 X-IronPort-AV: E=Sophos;i="5.22,518,1449504000"; d="scan'208";a="14132861" Subject: Re: [PATCH 1/2] btrfs: drop trace_btrfs_all_work_done() from normal_work_helper() To: Sebastian Andrzej Siewior References: <20161214140530.6534-1-bigeasy@linutronix.de> <20161220172613.GQ3620@twin.jikos.cz> <20161221082837.76yw5brgr7wovx6y@linutronix.de> CC: , Chris Mason , Josef Bacik , David Sterba , , From: Qu Wenruo Message-ID: <8e0e7bfd-8066-eb73-5180-376a182d7e60@cn.fujitsu.com> Date: Wed, 21 Dec 2016 16:45:06 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <20161221082837.76yw5brgr7wovx6y@linutronix.de> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.167.226.34] X-yoursite-MailScanner-ID: 59BFE477B1DF.A3296 X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: quwenruo@cn.fujitsu.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2000 Lines: 75 At 12/21/2016 04:28 PM, Sebastian Andrzej Siewior wrote: > On 2016-12-21 08:33:03 [+0800], Qu Wenruo wrote: >> The trace point only uses the pointer, and this helps us to pair with >> btrfs_work_queued/sched. > > | /* For situiations that the work is freed */ > | DECLARE_EVENT_CLASS(btrfs__work__done, > | > | TP_PROTO(struct btrfs_work *work), > | > | TP_ARGS(work), > | > | TP_STRUCT__entry_btrfs( > | __field( void *, work ) > | ), > | > | TP_fast_assign_btrfs(btrfs_work_owner(work), > | __entry->work = work; > | ), > | > | TP_printk_btrfs("work->%p", __entry->work) > | ); > > and btrfs_work_owner exapnds to: > > | struct btrfs_fs_info * > | btrfs_work_owner(struct btrfs_work *work) > | { > | return work->wq->fs_info; > | } > > voilà Oh I got it, thanks very much. The btrfs_work_owner() is newly introduced, no wonder I didn't know that. I think we can fix it by extracting fs_info pointer before running the work, and using the extracted one in the trace point. Thanks, Qu > >> But I still don't understand why backtrace is triggered. >> Since we're just recording a pointer, not touching it. >> >> Would you please explain the problem with more details on how it trigger the >> problem? > > enabled all events played with the fs which was just an upgrade and git > tree sync + checkout so nothing special. > >>> >>> So I think we should either remove the tracepoint completely or change >>> the arguments to take something else than a potentially freed 'work'. >> >> I'm mostly OK to remove the tracepoint, but such all_workd_done() trace >> should still help to determine if it's a workqueue stalled. >> >> Thanks, >> Qu > > Sebastian > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > >