From: David Vrabel <david.vrabel@citrix.com>
To: Ross Lagerwall <ross.lagerwall@citrix.com>,
xen-devel@lists.xenproject.org
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
David Vrabel <david.vrabel@citrix.com>
Subject: Re: [PATCH] xen/manage: Always freeze/thaw processes when suspend/resuming
Date: Fri, 22 Aug 2014 12:00:57 +0100 [thread overview]
Message-ID: <53F722E9.4060505@citrix.com> (raw)
In-Reply-To: <1408354896-30770-1-git-send-email-ross.lagerwall@citrix.com>
On 18/08/14 10:41, Ross Lagerwall wrote:
> Always freeze processes when suspending and thaw processes when resuming
> to prevent a race noticeable with HVM guests.
>
> This prevents a deadlock where the khubd kthread (which is designed to
> be freezable) acquires a usb device lock and then tries to allocate
> memory which requires the disk which hasn't been resumed yet.
> Meanwhile, the xenwatch thread deadlocks waiting for the usb device
> lock.
>
> Freezing processes fixes this because the khubd thread is only thawed
> after the xenwatch thread finishes resuming all the devices.
I think this is the safest fix for this issue but I'm a bit concerned
about how much extra time the freeze_processes() call will add to the
suspend.
Can you measure how long it takes for a typical VM?
David
next prev parent reply other threads:[~2014-08-22 11:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-18 9:41 [PATCH] xen/manage: Always freeze/thaw processes when suspend/resuming Ross Lagerwall
2014-08-22 11:00 ` David Vrabel [this message]
2014-08-22 14:39 ` Ross Lagerwall
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