From: Olaf Hering <olaf@aepfle.de>
To: Ian Campbell <Ian.Campbell@citrix.com>, Keir Fraser <keir.xen@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Jeremy Fitzhardinge <jeremy@goop.org>,
Konrad <konrad.wilk@oracle.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Subject: Re: [Xen-devel] [PATCH 1/3] xen/pv-on-hvm kexec: prevent crash in xenwatch_thread() when stale watch events arrive
Date: Wed, 17 Aug 2011 14:51:27 +0200 [thread overview]
Message-ID: <20110817125127.GA3163@aepfle.de> (raw)
In-Reply-To: <1313504072.5010.120.camel@zakaz.uk.xensource.com>
On Tue, Aug 16, Ian Campbell wrote:
> On Tue, 2011-08-16 at 14:16 +0100, Olaf Hering wrote:
> > During repeated kexec boots xenwatch_thread() can crash because
> > xenbus_watch->callback is cleared by xenbus_watch_path() if a node/token
> > combo for a new watch happens to match an already registered watch from
> > an old kernel. In this case xs_watch returns -EEXISTS, then
> > register_xenbus_watch() does not remove the to-be-registered watch from
> > the list of active watches but returns the -EEXISTS to the caller
> > anyway.
>
> Isn't this behaviour the root cause of the issue (which should be fixed)
> rather than papering over it during watch processing. IOW should't
> register_xenbus_watch cleanup after itself if xs_watch fails.
Keir, the EEXISTS case in register_xenbus_watch() was added by you 6
years ago. Do you happen to know what it tried to solve, and do these
conditions still apply today? Perhaps the EEXISTS can be removed now.
http://xenbits.xen.org/hg/xen-unstable.hg/diff/8016551fde98/linux-2.6-xen-sparse/drivers/xen/xenbus/xenbus_xs.c
Olaf
next prev parent reply other threads:[~2011-08-17 12:52 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-16 13:16 [PATCH 0/3] [v5] kexec and kdump for Xen PVonHVM guests Olaf Hering
2011-08-16 13:16 ` [PATCH 1/3] xen/pv-on-hvm kexec: prevent crash in xenwatch_thread() when stale watch events arrive Olaf Hering
2011-08-16 14:14 ` [Xen-devel] " Ian Campbell
2011-08-17 12:51 ` Olaf Hering [this message]
2011-08-17 13:30 ` Keir Fraser
2011-08-17 13:30 ` Keir Fraser
2011-08-16 13:16 ` [PATCH 2/3] xen/pv-on-hvm kexec: rebind virqs to existing eventchannel ports Olaf Hering
2011-08-16 13:16 ` [PATCH 3/3] xen/pv-on-hvm kexec+kdump: reset PV devices in kexec or crash kernel Olaf Hering
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