* [BUG] race condition in blkfront (probably other frontends too).
@ 2008-07-24 14:15 Gerd Hoffmann
2008-07-24 14:23 ` Keir Fraser
0 siblings, 1 reply; 3+ messages in thread
From: Gerd Hoffmann @ 2008-07-24 14:15 UTC (permalink / raw)
To: Xen Development Mailing List
Hi folks,
I've just seen it with the block frontend, but most likely the other
frontend drivers are affected too. The blkfront drivers goes into
initialized state (in blkfront_probe), and *after* that xenbus_dev_probe
sets a watch on the state node of the device. That leaves a race window
open for the backend going into connected state before the watch is
active. If that happens the frontend doesn't notice the backend is
ready and never ever goes into connected state ...
cheers,
Gerd
--
http://kraxel.fedorapeople.org/xenner/
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [BUG] race condition in blkfront (probably other frontends too).
2008-07-24 14:15 [BUG] race condition in blkfront (probably other frontends too) Gerd Hoffmann
@ 2008-07-24 14:23 ` Keir Fraser
2008-07-24 15:31 ` Gerd Hoffmann
0 siblings, 1 reply; 3+ messages in thread
From: Keir Fraser @ 2008-07-24 14:23 UTC (permalink / raw)
To: Gerd Hoffmann, Xen Development Mailing List
On 24/7/08 15:15, "Gerd Hoffmann" <kraxel@redhat.com> wrote:
> I've just seen it with the block frontend, but most likely the other
> frontend drivers are affected too. The blkfront drivers goes into
> initialized state (in blkfront_probe), and *after* that xenbus_dev_probe
> sets a watch on the state node of the device. That leaves a race window
> open for the backend going into connected state before the watch is
> active. If that happens the frontend doesn't notice the backend is
> ready and never ever goes into connected state ...
xenstored fires a watch immediately when it is registered. That should deal
with this particular race. Unless the watch gets discarded at the top of
otherend_changed() for some reason? I think you need to delve into this
issue a bit more, I'm afraid.
-- Keir
^ permalink raw reply [flat|nested] 3+ messages in thread
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2008-07-24 14:15 [BUG] race condition in blkfront (probably other frontends too) Gerd Hoffmann
2008-07-24 14:23 ` Keir Fraser
2008-07-24 15:31 ` Gerd Hoffmann
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