linux-kernel - Re: [PATCH V2 3/3] block: model freeze & enter queue as lock for supporting lockdep

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Message-ID: <ZyITwN0ihIFiz9M2@fedora>
Date: Wed, 30 Oct 2024 19:08:48 +0800
From: Ming Lei <ming.lei@...hat.com>
To: "Lai, Yi" <yi1.lai@...ux.intel.com>
Cc: Jens Axboe <axboe@...nel.dk>, linux-block@...r.kernel.org,
	Christoph Hellwig <hch@....de>,
	Peter Zijlstra <peterz@...radead.org>,
	Waiman Long <longman@...hat.com>, Boqun Feng <boqun.feng@...il.com>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	linux-kernel@...r.kernel.org, Bart Van Assche <bvanassche@....org>,
	yi1.lai@...el.com, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH V2 3/3] block: model freeze & enter queue as lock for
 supporting lockdep

On Wed, Oct 30, 2024 at 06:39:13PM +0800, Lai, Yi wrote:
> On Wed, Oct 30, 2024 at 05:50:15PM +0800, Ming Lei wrote:
> > On Wed, Oct 30, 2024 at 4:51 PM Lai, Yi <yi1.lai@...ux.intel.com> wrote:
> > >
> > > On Wed, Oct 30, 2024 at 03:13:09PM +0800, Ming Lei wrote:
> > > > On Wed, Oct 30, 2024 at 02:45:03PM +0800, Lai, Yi wrote:
> > ...
> > > >
> > > > It should be addressed by the following patch:
> > > >
> > > > https://lore.kernel.org/linux-block/ZyEGLdg744U_xBjp@fedora/
> > > >
> > >
> > > I have applied proposed fix patch on top of next-20241029. Issue can
> > > still be reproduced.
> > >
> > > It seems the dependency chain is different from Marek's log and mine.
> > 
> > Can you post the new log since q->q_usage_counter(io)->fs_reclaim from
> > blk_mq_init_sched is cut down by the patch?
> >
> 
> New possible deadlock log after patch applied:

This one looks like one real deadlock, any memory allocation with
q->sysfs_lock held has such risk.

There is another similar report related with queue sysfs store operation:

https://lore.kernel.org/linux-scsi/ZxG38G9BuFdBpBHZ@fedora/
 



Thanks,
Ming