From: Ian Jackson <ian.jackson@eu.citrix.com>
To: Wei Liu <wei.liu2@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>,
Ian Jackson <ian.jackson@eu.citrix.com>,
Fatih Acar <fatih.acar@gandi.net>
Subject: Re: [PATCH 2/2] xl: disable events earlier for shutdown event
Date: Thu, 2 Feb 2017 16:05:08 +0000 [thread overview]
Message-ID: <22675.22708.295615.110064@mariner.uk.xensource.com> (raw)
In-Reply-To: <20170202160006.65iuief63vt2m6h3@citrix.com>
Wei Liu writes ("Re: [PATCH 2/2] xl: disable events earlier for shutdown event"):
> On Thu, Feb 02, 2017 at 03:52:41PM +0000, Ian Jackson wrote:
> > But I think I don't really understand what the original bug is.
>
> The original bug is that:
Ah.
> 1. boot a guest with no disks, so diskws is NULL, num_disks == 0
> 2. some removable disks are added, and domain config updated
> 3. guest reboots, xl gets shutdown event
> 4. handle_domain_death gets the latest d_config, num_disks != 0 now
> 5. try to disable disk eject events with evdisable_disk_ejects -> BOOM
>
> So basically 5 needs to happen before 4. Moving that snippet seems to do
> the trick, and then freeing diskws + setting it to NULL makes the
> reboot path automatically re-register diskws.
Surely the right answer is to make evdisable_disk_ejects tolerate
whatever it finds in diskws (including diskws==NULL). It could be
idempotent too.
That way nothing depends on the exact ordering.
Ian.
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next prev parent reply other threads:[~2017-02-02 16:06 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-02 15:46 [PATCH 0/2] xl: event machinery fixes Wei Liu
2017-02-02 15:46 ` [PATCH 1/2] xl: free event in DOMAIN_RESTART_RENAME error path Wei Liu
2017-02-02 16:22 ` Wei Liu
2017-02-03 11:57 ` Ian Jackson
2017-02-02 15:46 ` [PATCH 2/2] xl: disable events earlier for shutdown event Wei Liu
2017-02-02 15:52 ` Ian Jackson
2017-02-02 16:00 ` Wei Liu
2017-02-02 16:05 ` Ian Jackson [this message]
2017-02-02 16:22 ` Wei Liu
2017-02-02 16:24 ` Ian Jackson
2017-02-03 9:46 ` Fatih Acar
2017-02-03 11:08 ` Wei Liu
2017-02-03 12:06 ` [PATCH 0/2] xl: event machinery fixes Wei Liu
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