From: Jan Beulich <jbeulich@suse.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Henry.Wang@arm.com, "Andrew Cooper" <andrew.cooper3@citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Wei Liu" <wl@xen.org>, "Edwin Török" <edvin.torok@citrix.com>,
xen-devel@lists.xenproject.org
Subject: Re: [PATCH for-4.17?] x86/paging: return -EINVAL for paging domctls for dying domains
Date: Wed, 9 Nov 2022 11:23:01 +0100 [thread overview]
Message-ID: <afbc37a1-99cb-ea09-575e-dc6448cd6f92@suse.com> (raw)
In-Reply-To: <Y2t87YE5acLfiClF@Air-de-Roger>
On 09.11.2022 11:11, Roger Pau Monné wrote:
> On Wed, Nov 09, 2022 at 08:48:46AM +0100, Jan Beulich wrote:
>> Finally I'm not convinced of the usefulness of this dying check in the
>> first place: is_dying may become set immediately after the check was
>> done.
>
> While strictly true, this code is executed with the domain lock held,
> so while is_dying might change, domain_kill() won't make progress
> because of the barrier on the domain lock just after setting is_dying.
I guess I'm confused now: This code is called with the domctl lock
held, which - as said before - is a questionable thing, for serializing
things more than necessary as well as for holding this lock for
excessive periods of time. IOW I consider it wrong to depend on that
in paging_domctl() to synchronize against domain_kill(). Yet indeed that
should eliminate races at present.
Jan
next prev parent reply other threads:[~2022-11-09 10:23 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-08 11:38 [PATCH for-4.17?] x86/paging: return -EINVAL for paging domctls for dying domains Roger Pau Monne
2022-11-08 16:14 ` Jan Beulich
2022-11-08 16:43 ` Roger Pau Monné
2022-11-08 17:03 ` Jan Beulich
2022-11-08 17:15 ` Roger Pau Monné
2022-11-09 7:48 ` Jan Beulich
2022-11-09 9:45 ` Edwin Torok
2022-11-09 9:58 ` Jan Beulich
2022-11-09 10:11 ` Roger Pau Monné
2022-11-09 10:23 ` Jan Beulich [this message]
2022-11-09 11:36 ` Roger Pau Monné
2022-11-09 12:02 ` Jan Beulich
2022-11-09 13:22 ` Roger Pau Monné
2022-11-10 9:03 ` Jan Beulich
2022-11-08 17:30 ` Edwin Torok
2022-11-09 16:11 ` Andrew Cooper
2022-11-10 9:02 ` Jan Beulich
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