From: Fam Zheng <famz@redhat.com>
To: Roman Penyaev <roman.penyaev@profitbricks.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
Kevin Wolf <kwolf@redhat.com>, qemu-devel <qemu-devel@nongnu.org>,
qemu-block@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 3/3] linux-aio: fix re-entrant completion processing
Date: Wed, 28 Sep 2016 17:34:24 +0800 [thread overview]
Message-ID: <20160928093424.GA11641@lemon> (raw)
In-Reply-To: <CAJrWOzD2HTDqvS=GgxkjAaFY_7Sn6vEQsjdGBBC03iSfq7AjAQ@mail.gmail.com>
On Wed, 09/28 11:14, Roman Penyaev wrote:
> On Wed, Sep 28, 2016 at 5:01 AM, Fam Zheng <famz@redhat.com> wrote:
> > On Tue, 09/27 19:55, Roman Penyaev wrote:
> >> > The bug is 100% deterministic. Just boot up a guest with -drive
> >> > format=qcow2,aio=native.
> >>
> >> It turns out to be that everything is broken. I started all my
> >> tests with format=raw,aio=native and immediately got coroutine
> >> recursive. That is completely weird.
> >>
> >> So, what I did is the following:
> >>
> >> 1. Took latest master (nothing works)
> >> 2. Did interactive rebase to 12c8720
> >> 12c8720 2016-06-28 | Merge remote-tracking branch
> >> 'remotes/stefanha/tags/block-pull-request' into staging [Peter
> >> Maydell]
> >>
> >> this merge request includes all your patches related to
> >> virtio-blk and MQ support.
> >>
> >> 3. Applied 0ed93d84edab. Everything works fine.
> >
> > Have you tried qcow2 at this point? raw crashes with 1a62d0accdf85 doesn't mean
> > qcow2 is fine without it.
> >
>
> That's true. qcow2 IO path is different, and presence of the
> patch 1a62d0accdf85 does not affect - coroutine still enters
> recursively.
>
> But for me it is quite surprising that IO fragmentation (what
> was done in 1a62d0accdf85) rises the misbehavior on raw IO path.
Maybe the mystery with this change is your particular I/O pattern on the raw
image is change thereafter, from ioq = 1 to ioq > 1 (from the linux-aio.c's
PoV, due to fragmentation), then multiple coroutines are created for one big
request, to trigger the crash.
Fam
>
> But of course originally issue was introduced by me. Stefan,
> thanks for a fix.
>
> --
> Roman
next prev parent reply other threads:[~2016-09-28 9:34 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-27 14:06 [Qemu-devel] [PATCH 0/3] linux-aio: fix "Co-routine re-entered recursively" error Stefan Hajnoczi
2016-09-27 14:06 ` [Qemu-devel] [PATCH 1/3] coroutine: add qemu_coroutine_entered() function Stefan Hajnoczi
2016-09-27 16:20 ` Paolo Bonzini
2016-09-27 16:29 ` Stefan Hajnoczi
2016-09-27 16:55 ` Paolo Bonzini
2016-09-28 9:50 ` Kevin Wolf
2016-09-27 14:06 ` [Qemu-devel] [PATCH 2/3] test-coroutine: test qemu_coroutine_entered() Stefan Hajnoczi
2016-09-27 14:06 ` [Qemu-devel] [PATCH 3/3] linux-aio: fix re-entrant completion processing Stefan Hajnoczi
2016-09-27 14:29 ` Roman Penyaev
2016-09-27 15:25 ` Stefan Hajnoczi
2016-09-27 17:55 ` Roman Penyaev
2016-09-28 3:01 ` Fam Zheng
2016-09-28 9:14 ` Roman Penyaev
2016-09-28 9:34 ` Fam Zheng [this message]
2016-09-28 9:38 ` Roman Penyaev
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