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Date: Thu, 17 Mar 2011 10:21:59 +0200
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Jean-Philippe Menil <jean-philippe.menil@...v-nantes.fr>
Cc: netdev@...r.kernel.org, kvm@...r.kernel.org,
virtualization@...ts.linux-foundation.org
Subject: Re: Bug inkvm_set_irq
On Thu, Mar 17, 2011 at 09:00:30AM +0100, Jean-Philippe Menil wrote:
> >>Are you running a preemptible kernel?
> >>Does the following help at all?
> >>
> >>diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
> >>index 2ca4535..cdf51c9 100644
> >>--- a/virt/kvm/eventfd.c
> >>+++ b/virt/kvm/eventfd.c
> >>@@ -90,7 +90,7 @@ irqfd_shutdown(struct work_struct *work)
> >> * We know no new events will be scheduled at this point, so block
> >> * until all previously outstanding events have completed
> >> */
> >>- flush_work(&irqfd->inject);
> >>+ flush_work_sync(&irqfd->inject);
> >>
> >> /*
> >> * It is now safe to release the object's resources
> >>
> >Hi,
> >
> >thanks for the response.
> >
> >root@...shire:~# zcat /proc/config.gz | grep -i preempt
> ># CONFIG_PREEMPT_RCU is not set
> >CONFIG_PREEMPT_NOTIFIERS=y
> >CONFIG_PREEMPT_NONE=y
> ># CONFIG_PREEMPT_VOLUNTARY is not set
> ># CONFIG_PREEMPT is not set
> >
> >It does not seem to be a preemptible kernel.
> >
> >I will test tour patch, and report the result.
> >
> >Regards.
> >
> Hi,
>
> i reboot the host with the "flush_work_sync", yesterday at lunchtime.
> I haven't see "Eventfd bug detected" or "Wakeup bug detected" until now.
>
> The modification seem to do the trick.
>
> So, if my understand is correct, flush_work flush the last irqfd,
> but in my case, antoher irqfd was still queued to a cpu?
> Is that right?
>
> Regards.
Yes, it says:
* flush_work - wait for a work to finish executing the last queueing instance
* @work: the work to flush
*
* Wait until @work has finished execution. This function considers
* only the last queueing instance of @work. If @work has been
* enqueued across different CPUs on a non-reentrant workqueue or on
* multiple workqueues, @work might still be executing on return on
* some of the CPUs from earlier queueing.
*
* If @work was queued only on a non-reentrant, ordered or unbound
* workqueue, @work is guaranteed to be idle on return if it hasn't
* been requeued since flush started.
kvm uses the default workqueue which is non-reentrant.
Thanks to Gleb for the suggestion!
--
MST
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