From: "Michael S. Tsirkin" <mst@redhat.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Chris Wright <chrisw@redhat.com>,
"Hans J. Koch" <hjk@hansjkoch.de>,
Jesse Barnes <jbarnes@virtuousgeek.org>,
Greg Kroah-Hartman <gregkh@suse.de>,
Anthony Foiani <anthony.foiani@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] uio/gen-pci: don't enable interrupts in ISR
Date: Tue, 9 Aug 2011 15:02:07 +0300 [thread overview]
Message-ID: <20110809120206.GB524@redhat.com> (raw)
In-Reply-To: <4E411D72.7000604@linutronix.de>
On Tue, Aug 09, 2011 at 01:43:46PM +0200, Sebastian Andrzej Siewior wrote:
> Michael S. Tsirkin wrote:
> >>It seems to me that you could drop this "user block" thing
> >>since you never change anything outside of this command register and it
> >>does not stop the race.
> >
> >I don't think so: if we did, we would lose userspace modifications to
> >other bits such as io enable, and there's no way to guess what their
> >values should be.
>
> How so?
>
> Sebastian
Let's assume we start with e.g. io enable bit cleared.
user kernel
read config |
set io enable |
| interrupt
| read + set interrupt mask
write config back |
write
We end up with io enable bit cleared. Locking around rmw
that we have fixes this race.
--
MST
next prev parent reply other threads:[~2011-08-09 12:01 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-04 20:46 [PATCH] uio/gen-pci: don't enable interrupts in ISR Sebastian Andrzej Siewior
2011-08-04 21:04 ` Michael S. Tsirkin
2011-08-05 0:15 ` Hans J. Koch
2011-08-08 6:24 ` Michael S. Tsirkin
2011-08-08 17:19 ` Hans J. Koch
2011-08-09 11:37 ` Michael S. Tsirkin
2011-08-09 18:53 ` Hans J. Koch
2011-08-10 8:40 ` Michael S. Tsirkin
2011-08-23 0:49 ` [stable] " Greg KH
2011-08-23 8:40 ` Sebastian Andrzej Siewior
2011-08-23 10:57 ` Hans J. Koch
2011-08-23 11:00 ` Hans J. Koch
2011-08-05 19:18 ` Sebastian Andrzej Siewior
2011-08-08 6:40 ` Michael S. Tsirkin
2011-08-09 11:43 ` Sebastian Andrzej Siewior
2011-08-09 12:02 ` Michael S. Tsirkin [this message]
2011-08-10 8:33 ` Sebastian Andrzej Siewior
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