From: "Daniel P. Berrangé" <berrange@redhat.com>
To: Markus Armbruster <armbru@redhat.com>
Cc: chenjiashang@huawei.com, qemu-devel@nongnu.org,
Peter Xu <peterx@redhat.com>,
"Gonglei \(Arei\)" <arei.gonglei@huawei.com>,
pbonzini@redhat.com, marcandre.lureau@redhat.com,
"Longpeng \(Mike,
Cloud Infrastructure Service Product Dept.\)"
<longpeng2@huawei.com>
Subject: Re: A bug of Monitor Chardev ?
Date: Tue, 8 Jun 2021 16:37:11 +0100 [thread overview]
Message-ID: <YL+Op6F7wFoVYum2@redhat.com> (raw)
In-Reply-To: <87o8cgxxel.fsf@dusky.pond.sub.org>
On Tue, Jun 08, 2021 at 04:07:30PM +0200, Markus Armbruster wrote:
> "Longpeng (Mike, Cloud Infrastructure Service Product Dept.)"
> <longpeng2@huawei.com> writes:
>
> > We find a race during QEMU starting, which would case the QEMU process coredump.
> >
> > <main loop> | <MON iothread>
> > |
> > [1] create MON chardev |
> > qemu_create_early_backends |
> > chardev_init_func |
> > |
> > [2] create MON iothread |
> > qemu_create_late_backends |
> > mon_init_func |
> > aio_bh_schedule-----------------------> monitor_qmp_setup_handlers_bh
> > [3] enter main loog | tcp_chr_update_read_handler
> > (* A client come in, e.g. Libvirt *) | update_ioc_handlers
> > tcp_chr_new_client |
> > update_ioc_handlers |
> > |
> > [4] create new hup_source |
> > s->hup_source = *PTR1* |
> > g_source_attach(s->hup_source)|
> > | [5] remove_hup_source(*PTR1*)
> > | (create new hup_source)
> > | s->hup_source = *PTR2*
> > [6] g_source_attach_unlocked |
> > *PTR1* is freed by [5] |
> >
> > Do you have any suggestion to fix this bug ? Thanks!
>
> Do we? We talked, but I'm not sure we reached a conclusion.
Seems like we ended up with two options.
1. A workaround for the current specific problem by rearranging
the initilization code in the monitor a little.
2. A design fix of splitting the chardev creation into two
parts, one creation, and one activation.
The latter is significantly more work, but is a better long term bet IMHO.
But what we really is someone motivated to actually implement one of the
two options.
Regards,
Daniel
--
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next prev parent reply other threads:[~2021-06-08 15:38 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-17 6:56 A bug of Monitor Chardev ? Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-05-19 16:17 ` Marc-André Lureau
2021-05-19 16:40 ` Daniel P. Berrangé
2021-05-21 7:25 ` Markus Armbruster
2021-05-21 14:43 ` Peter Xu
2021-05-21 16:33 ` Daniel P. Berrangé
2021-05-21 16:56 ` Daniel P. Berrangé
2021-05-21 16:59 ` Marc-André Lureau
2021-05-21 17:07 ` Daniel P. Berrangé
2021-05-21 17:14 ` Peter Xu
2021-05-25 6:53 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-05-21 17:09 ` Peter Xu
2021-05-21 17:15 ` Daniel P. Berrangé
2021-06-08 14:07 ` Markus Armbruster
2021-06-08 15:37 ` Daniel P. Berrangé [this message]
2021-06-09 0:20 ` Longpeng (Mike, Cloud Infrastructure Service Product Dept.)
2021-06-09 10:13 ` Marc-André Lureau
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