From: Juan Quintela <quintela@redhat.com>
To: Laurent Vivier <lvivier@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [PATCH] runstate: ignore finishmigrate -> prelaunch transition
Date: Wed, 08 Jan 2020 13:39:36 +0100 [thread overview]
Message-ID: <87imlmi0l3.fsf@secure.laptop> (raw)
In-Reply-To: <e0557fa4-e5b3-3f83-e002-b22d81e7561f@redhat.com> (Laurent Vivier's message of "Wed, 18 Dec 2019 17:21:17 +0100")
Laurent Vivier <lvivier@redhat.com> wrote:
> Ping?
>
> Thanks,
> Laurent
>
> On 12/12/2019 20:40, Laurent Vivier wrote:
>> On 06/12/2019 20:52, Dr. David Alan Gilbert wrote:
>>> * Laurent Vivier (lvivier@redhat.com) wrote:
>>>> Commit 1bd71dce4bf2 tries to prevent a finishmigrate -> prelaunch
>>>> transition by exiting at the beginning of the main_loop_should_exit()
>>>> function if the state is already finishmigrate.
>>>>
>>>> As the finishmigrate state is set in the migration thread it can
>>>> happen concurrently to the function. The migration thread and the
>>>> function are normally protected by the iothread mutex and thus the
>>>> state should no evolve between the start of the function and its end.
>>>>
>>>> Unfortunately during the function life the lock is released by
>>>> pause_all_vcpus() just before the point we need to be sure we are
>>>> not in finishmigrate state and if the migration thread is waiting
>>>> for the lock it will take the opportunity to change the state
>>>> to finishmigrate.
>>>
>>> Ewww.
>>> I hate those short wakeups for pause_all_vcpus; I'm sure there are loads
>>> more corners that break.
>>>
>>> Still, I _think_ this is an improvement, so:
>>>
>>> Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
>>>
>>
>> Who volunteers to take this in his queue?
Reviewed-by: Juan Quintela <quintela@redhat.com>
queued
prev parent reply other threads:[~2020-01-08 13:02 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-29 11:51 [PATCH] runstate: ignore finishmigrate -> prelaunch transition Laurent Vivier
2019-12-06 19:52 ` Dr. David Alan Gilbert
2019-12-12 19:40 ` Laurent Vivier
2019-12-18 16:21 ` Laurent Vivier
2019-12-18 16:52 ` Dr. David Alan Gilbert
2020-01-08 12:39 ` Juan Quintela [this message]
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