From: Julien Grall <julien@xen.org>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Jürgen Groß" <jgross@suse.com>,
xen-devel@lists.xenproject.org,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Ian Jackson" <iwj@xenproject.org>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Wei Liu" <wl@xen.org>
Subject: Re: [PATCH v2 1/2] xen/events: access last_priority and last_vcpu_id together
Date: Tue, 20 Oct 2020 11:01:11 +0100 [thread overview]
Message-ID: <244a4487-044b-5813-dd03-fe4ff5aac3b3@xen.org> (raw)
In-Reply-To: <abaf4b52-df8d-6df0-9100-a4c9884c09da@suse.com>
On 20/10/2020 10:34, Jan Beulich wrote:
> On 20.10.2020 11:25, Julien Grall wrote:
>> Given that evtchn->last_vcpu_id and evtchn->last_priority can only be
>> modified in evtchn_fifo_set_pending(), this suggests that it is expected
>> for the function to multiple called concurrently on the same event channel.
>>
>>> I'm unconvinced it was really considered
>>> whether racing sending on the same channel is also safe this way.
>>
>> How would you explain the 3 try in lock_old_queue then?
>
> Queue changes (as said by the gprintk()) can't result from sending
> alone, but require re-binding to a different vCPU or altering the
> priority.
I agree with that. However, this doesn't change the fact that update to
evtchn->last_priority and evtchn->last_vcpu can only happen when calling
evtchn_fifo_set_pending().
If evtchn_fifo_set_pending() cannot be called concurrently for the same
event, then there is *no* way for evtchn->last_{priority, vcpu} to be
updated concurrently.
> I'm simply unconvinced that the code indeed fully reflects
> the original intentions.
Do you mind (re-)sharing what was the original intentions?
Cheers,
--
Julien Grall
next prev parent reply other threads:[~2020-10-20 10:01 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-12 9:27 [PATCH v2 0/2] XSA-343 followup patches Juergen Gross
2020-10-12 9:27 ` [PATCH v2 1/2] xen/events: access last_priority and last_vcpu_id together Juergen Gross
2020-10-12 9:48 ` Paul Durrant
2020-10-12 9:56 ` Jürgen Groß
2020-10-12 10:06 ` Paul Durrant
2020-10-13 13:58 ` Jan Beulich
2020-10-13 14:20 ` Jürgen Groß
2020-10-13 14:26 ` Jan Beulich
2020-10-14 11:40 ` Julien Grall
2020-10-15 12:07 ` Jan Beulich
2020-10-16 5:46 ` Jürgen Groß
2020-10-16 9:36 ` Julien Grall
2020-10-16 12:09 ` Jan Beulich
2020-10-20 9:25 ` Julien Grall
2020-10-20 9:34 ` Jan Beulich
2020-10-20 10:01 ` Julien Grall [this message]
2020-10-20 10:06 ` Jan Beulich
2020-10-12 9:27 ` [PATCH v2 2/2] xen/evtchn: rework per event channel lock Juergen Gross
2020-10-13 14:02 ` Jan Beulich
2020-10-13 14:13 ` Jürgen Groß
2020-10-13 15:30 ` Jan Beulich
2020-10-13 15:28 ` Jan Beulich
2020-10-14 6:00 ` Jürgen Groß
2020-10-14 6:52 ` Jan Beulich
2020-10-14 7:27 ` Jürgen Groß
2020-10-16 9:51 ` Julien Grall
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