From: David Jeffery <djeffery@redhat.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@kernel.dk>,
Christoph Hellwig <hch@lst.de>,
Bart Van Assche <bvanassche@acm.org>,
stefanha@redhat.com, linux-block@vger.kernel.org,
linux-scsi@vger.kernel.org,
virtualization@lists.linux-foundation.org
Subject: Re: [Bug] double ->queue_rq() because of timeout in ->queue_rq()
Date: Fri, 21 Oct 2022 14:33:21 -0400 [thread overview]
Message-ID: <CA+-xHTFp+gFVy6aKW2nj47+WY2+1vOLAE-X067C-hm4_8ngA6g@mail.gmail.com> (raw)
In-Reply-To: <Y1K5Oo7bIRlVTDnb@T590>
On Fri, Oct 21, 2022 at 11:22 AM Ming Lei <ming.lei@redhat.com> wrote:
>
> On Fri, Oct 21, 2022 at 08:32:31AM -0600, Keith Busch wrote:
> >
> > I agree with your idea that this is a lower level driver responsibility:
> > it should reclaim all started requests before allowing new queuing.
> > Perhaps the block layer should also raise a clear warning if it's
> > queueing a request that's already started.
>
> The thing is that it is one generic issue, lots of VM drivers could be
> affected, and it may not be easy for drivers to handle the race too.
>
While virtual systems are a common source of the problem, fully
preempt kernels (with or without real-time patches) can also trigger
this condition rather simply with a poorly behaved real-time task. The
involuntary preemption means the queue_rq call can be stopped to let
another task run. Poorly behaving tasks claiming the CPU for longer
than the request timeout when preempting a task in a queue_rq function
could cause the condition on real or virtual hardware. So it's not
just VM related drivers that are affected by the race.
David Jeffery
next prev parent reply other threads:[~2022-10-21 18:33 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-20 9:10 [Bug] double ->queue_rq() because of timeout in ->queue_rq() Ming Lei
2022-10-20 9:10 ` Ming Lei
2022-10-20 20:01 ` Stefan Hajnoczi
2022-10-20 20:01 ` Stefan Hajnoczi
2022-10-21 2:23 ` Ming Lei
2022-10-21 2:23 ` Ming Lei
2022-10-24 15:30 ` Stefan Hajnoczi
2022-10-24 15:30 ` Stefan Hajnoczi
2022-10-24 15:41 ` Ming Lei
2022-10-24 15:41 ` Ming Lei
2022-10-20 20:26 ` Bart Van Assche
2022-10-20 20:26 ` Bart Van Assche
2022-10-21 0:57 ` Ming Lei
2022-10-21 0:57 ` Ming Lei
2022-10-21 14:32 ` Keith Busch
2022-10-21 15:22 ` Ming Lei
2022-10-21 15:22 ` Ming Lei
2022-10-21 18:33 ` David Jeffery [this message]
2022-10-22 4:27 ` Ming Lei
2022-10-22 4:27 ` Ming Lei
2022-10-21 18:21 ` David Jeffery
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