From mboxrd@z Thu Jan 1 00:00:00 1970 From: John Stultz Subject: Re: 2.6.39 crashes BUG: unable to handle kernel NULL pointer dereference at 000000000000042 .. cmos_checkintr+0x4d/0x55 under Xen as PV guest. Date: Mon, 21 Mar 2011 12:40:00 -0700 Message-ID: <1300736400.2731.66.camel@work-vm> References: <20110318203830.GA9262@dumpdata.com> <1300485566.2731.46.camel@work-vm> <20110319025134.GA3298@dumpdata.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20110319025134.GA3298@dumpdata.com> Sender: linux-kernel-owner@vger.kernel.org To: Konrad Rzeszutek Wilk Cc: tglx@linutronix.de, linux-kernel@vger.kernel.org, xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org On Fri, 2011-03-18 at 22:51 -0400, Konrad Rzeszutek Wilk wrote: > On Fri, Mar 18, 2011 at 02:59:26PM -0700, John Stultz wrote: > > On Fri, 2011-03-18 at 16:38 -0400, Konrad Rzeszutek Wilk wrote: > > > With the latest linus/master I get this when starting a Xen Linux PV > > > guest: > > > > > > [ 0.404760] initcall psmouse_init+0x0/0x79 returned 0 after 59 usecs > > > [ 0.404767] calling cmos_init+0x0/0x6a @ 1 > > > [ 0.464855] BUG: unable to handle kernel NULL pointer dereference at 0000000000000428 > > > [ 0.464867] IP: [] queue_work_on+0x4/0x1d > > [snip] > > > [ 0.465018] Call Trace: > > > [ 0.465023] [] queue_work+0x1a/0x1c > > > [ 0.465029] [] schedule_work+0x13/0x15 > > > [ 0.465035] [] rtc_update_irq+0x10/0x12 > > > [ 0.465041] [] cmos_checkintr+0x4d/0x55 > > > [ 0.465047] [] cmos_irq_disable+0x46/0x4e > > > [ 0.465051] [] cmos_set_alarm+0xd9/0x16e > > > [ 0.465051] [] __rtc_set_alarm+0x7d/0x88 > > > [ 0.465051] [] rtc_timer_enqueue+0x71/0xb8 > > > [ 0.465051] [] ? rtc_tm_to_time+0x2f/0x38 > > > > > > ... full log at the end. > > > > > > From a brief look it looks as if rtc_device_register was never > > > called, so > > > > > > INIT_WORK(&rtc->irqwork, rtc_timer_do_work); > > > > > > was never called.. and hence schedule_work tries to derefence an > > > unitialized rtc->irqwork. > > > > > > Which actually sounds right - the rtc_device_register should not > > > be called since there are no RTC clocks exposed. > > > > > > Huh. Did you see this with 2.6.38 vanilla? Just want to clarify if this > > No. 2.6.38 vaniall works great. Ok. Hrm. > > Any insight there? > > I hoped you might have :-) Could you help me understand where in the probe logic xen bombs out of the cmos code? thanks -john