From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wei Liu <Wei.Liu2@citrix.com>
Subject: Re: HVM bug: system crashes after offline online a vcpu
Date: Thu, 20 Dec 2012 17:48:21 +0000
Message-ID: <1356025701.24056.3.camel@iceland>
References: <1355411537.8376.52.camel@iceland>
	<20121219160455.GA12077@phenom.dumpdata.com>
	<1355936517.10526.28.camel@iceland>
	<20121219174000.GA28570@phenom.dumpdata.com>
	<1355939543.10526.30.camel@iceland>
	<20121219192405.GA24729@phenom.dumpdata.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: 7bit
Return-path: <xen-devel-bounces@lists.xen.org>
In-Reply-To: <20121219192405.GA24729@phenom.dumpdata.com>
List-Unsubscribe: <http://lists.xen.org/cgi-bin/mailman/options/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=unsubscribe>
List-Post: <mailto:xen-devel@lists.xen.org>
List-Help: <mailto:xen-devel-request@lists.xen.org?subject=help>
List-Subscribe: <http://lists.xen.org/cgi-bin/mailman/listinfo/xen-devel>,
	<mailto:xen-devel-request@lists.xen.org?subject=subscribe>
Sender: xen-devel-bounces@lists.xen.org
Errors-To: xen-devel-bounces@lists.xen.org
To: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: wei.liu2@citrix.com, "xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
List-Id: xen-devel@lists.xenproject.org

On Wed, 2012-12-19 at 19:24 +0000, Konrad Rzeszutek Wilk wrote:
> #
> #
> # # echo 0 > /sys/devices/system/cpu/cpu3/onlineecho 0 > /sys/devices/system/cpu/cpu3/online 1 > /sys/devices/system/cpu/cpu3/online > /sys/devices/system/cpu/cpu3/online
> [   73.324141] installing Xen timer for CPU 3
> [   73.324236] cpu 3 spinlock event irqc_intel fbcon scsi_mod tileblit font bitblit softcursor atl1c drm_kms_helper video xen_blkfront xen_netfront fb_sys_fops sysimgblt sysfillrect syscopyarea xenfs xen_privcmd mperf
> [   73.325026] Pid: 0, comm: swapper/3 Not tainted 3.7.0upstream #1
> [   73.325033] Call Trace:
> [   73.325047]  [<ffffffff810c2d1d>] __schedule_bug+0x4d/0x60
> [   73.325058]  [<ffffffff816359e2>] __schedule+0x6b2/0x7c0
> [   73.325074]  [<ffffffff81043d5d>] ? xen_force_evtchn_callback+0xd/0x10
> [   73.325086]  [<ffffffff81635bb4>] schedule+0x24/0x70
> [   73.325097]  [<ffffffff81056de9>] cpu_idle+0xc9/0xe0
> [   73.325112]  [<ffffffff810445b9>] ? xen_irq_enable_direct_reloc+0x4/0x4
> [   73.325116] BUG: unable to handle kernel NULL pointer dereference[   73.325122]  [<ffffffff8162572b>] cpu_bringup_and_idle+0xe/0x10
> 

The thread is a bit off-topic now since we're talking about PV at the
moment...

Please see cs 41bd956de3dfdc3a43708fe2e0c8096c69064a1e, it seems that
the imbalance still exists with CONFIG_PREEMPT_COUNT=y.

And I didn't manage to reproduce the NULL pointer deference.


Wei.