From: Paolo Bonzini <pbonzini@redhat.com>
To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: qemu-devel <qemu-devel@nongnu.org>,
"open list:Block layer core" <qemu-block@nongnu.org>,
Hanna Reitz <hreitz@redhat.com>, Kevin Wolf <kwolf@redhat.com>,
Fam Zheng <fam@euphon.net>, Qing Wang <qinwang@redhat.com>,
Emanuele Giuseppe Esposito <eesposit@redhat.com>
Subject: Re: [PATCH] block-backend: fix virtio-scsi assertion failure with blk_drain_noref()
Date: Thu, 5 Jan 2023 12:59:21 +0100 [thread overview]
Message-ID: <CABgObfZ4-89bwi-LLddbw3Of-pYNHfjSo01G7Ej0J7__Yth0vg@mail.gmail.com> (raw)
In-Reply-To: <Y7a14QNkit3keLm1@fedora>
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Il gio 5 gen 2023, 12:35 Stefan Hajnoczi <stefanha@redhat.com> ha scritto:
> On Wed, Jan 04, 2023 at 10:37:34PM +0100, Paolo Bonzini wrote:
> > blk_root_drained_end is not thread-safe too. I started looking at that
> with
> > https://www.mail-archive.com/qemu-devel@nongnu.org/msg925670.html;
> that's
> > certainly a prerequisite for this patch to be a full fix, but I have not
> > checked if it's enough because I don't have the QEMU sources at hand
> right
> > now.
>
> Thanks for letting me know.
>
> Do you think blk_drain_noref() makes sense at all, or should
> scsi_purge_requests() avoid calling blk_drain() somehow?
>
I think it makes sense as a stop gap measure.
Perhaps these iothread unrefs could also be changed to happen in a
main-loop BH, but I wouldn't rush that. Unref is also the main culprit for
functions that end up calling aio_poll from coroutine context (which should
be prohibited!) and Kevin was looking at that.
Paolo
> Stefan
>
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next prev parent reply other threads:[~2023-01-05 12:00 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-04 19:56 [PATCH] block-backend: fix virtio-scsi assertion failure with blk_drain_noref() Stefan Hajnoczi
2023-01-04 21:37 ` Paolo Bonzini
2023-01-05 11:34 ` Stefan Hajnoczi
2023-01-05 11:59 ` Paolo Bonzini [this message]
2023-01-13 15:31 ` Kevin Wolf
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