From: Vineeth Vijayan <vneethv@linux.ibm.com>
To: Halil Pasic <pasic@linux.ibm.com>, Cornelia Huck <cohuck@redhat.com>
Cc: Heiko Carstens <hca@linux.ibm.com>,
Vasily Gorbik <gor@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Pierre Morel <pmorel@linux.ibm.com>,
Michael Mueller <mimu@linux.ibm.com>,
linux-s390@vger.kernel.org,
virtualization@lists.linux-foundation.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, bfu@redhat.com
Subject: Re: [PATCH 1/1] virtio/s390: fix vritio-ccw device teardown
Date: Mon, 20 Sep 2021 09:41:06 +0200 [thread overview]
Message-ID: <88b514a4416cf72cda53a31ad2e15c13586350e4.camel@linux.ibm.com> (raw)
In-Reply-To: <20210920003935.1369f9fe.pasic@linux.ibm.com>
On Mon, 2021-09-20 at 00:39 +0200, Halil Pasic wrote:
> On Fri, 17 Sep 2021 10:40:20 +0200
> Cornelia Huck <cohuck@redhat.com> wrote:
>
...snip...
> > >
> > > Thanks, if I find time for it, I will try to understand this
> > > better and
> > > come back with my findings.
> > >
> > > > > * Can virtio_ccw_remove() get called while !cdev->online and
> > > > > virtio_ccw_online() is running on a different cpu? If yes,
> > > > > what would
> > > > > happen then?
> > > >
> > > > All of the remove/online/... etc. callbacks are invoked via the
> > > > ccw bus
> > > > code. We have to trust that it gets it correct :) (Or have the
> > > > common
> > > > I/O layer maintainers double-check it.)
> > > >
> > >
> > > Vineeth, what is your take on this? Are the struct ccw_driver
> > > virtio_ccw_remove and the virtio_ccw_online callbacks mutually
> > > exclusive. Please notice that we may initiate the onlining by
> > > calling ccw_device_set_online() from a workqueue.
> > >
> > > @Conny: I'm not sure what is your definition of 'it gets it
> > > correct'...
> > > I doubt CIO can make things 100% foolproof in this area.
> >
> > Not 100% foolproof, but "don't online a device that is in the
> > progress
> > of going away" seems pretty basic to me.
> >
>
> I hope Vineeth will chime in on this.
Considering the online/offline processing,
The ccw_device_set_offline function or the online/offline is handled
inside device_lock. Also, the online_store function takes care of
avoiding multiple online/offline processing.
Now, when we consider the unconditional remove of the device,
I am not familiar with the virtio_ccw driver. My assumptions are based
on how CIO/dasd drivers works. If i understand correctly, the dasd
driver sets different flags to make sure that a device_open is getting
prevented while the the device is in progress of offline-ing.
>
> > >
> > > > >
> > > > > The main addresse of these questions is Conny ;).
> > >
...snip...
next prev parent reply other threads:[~2021-09-20 7:41 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-15 21:57 [PATCH 1/1] virtio/s390: fix vritio-ccw device teardown Halil Pasic
2021-09-15 22:00 ` Halil Pasic
2021-09-16 8:59 ` Cornelia Huck
2021-09-16 13:18 ` Halil Pasic
2021-09-17 8:40 ` Cornelia Huck
2021-09-19 22:39 ` Halil Pasic
2021-09-20 7:41 ` Vineeth Vijayan [this message]
2021-09-20 10:07 ` Cornelia Huck
2021-09-21 3:25 ` Halil Pasic
2021-09-21 12:09 ` Cornelia Huck
2021-09-21 13:31 ` Vineeth Vijayan
2021-09-21 16:52 ` Halil Pasic
2021-09-21 18:25 ` Vineeth Vijayan
2021-09-20 10:30 ` Cornelia Huck
2021-09-20 13:27 ` Halil Pasic
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