From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Wed, 27 Jun 2018 17:41:51 +0100 Subject: [PATCH] arm64: fix infinite stacktrace In-Reply-To: <20180615115823.2oq5d7amzwlliczg@lakrids.cambridge.arm.com> References: <20180615115823.2oq5d7amzwlliczg@lakrids.cambridge.arm.com> Message-ID: <20180627164150.GB8729@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi all, On Fri, Jun 15, 2018 at 12:58:23PM +0100, Mark Rutland wrote: > On Thu, Jun 14, 2018 at 02:58:21PM -0400, Mikulas Patocka wrote: > > I've got this infinite stacktrace when debugging another problem: > > [ 908.795225] INFO: rcu_preempt detected stalls on CPUs/tasks: > > [ 908.796176] 1-...!: (1 GPs behind) idle=952/1/4611686018427387904 softirq=1462/1462 fqs=355 > > [ 908.797692] 2-...!: (1 GPs behind) idle=f42/1/4611686018427387904 softirq=1550/1551 fqs=355 > > [ 908.799189] (detected by 0, t=2109 jiffies, g=130, c=129, q=235) > > [ 908.800284] Task dump for CPU 1: > > [ 908.800871] kworker/1:1 R running task 0 32 2 0x00000022 > > [ 908.802127] Workqueue: writecache-writeabck writecache_writeback [dm_writecache] > > [ 908.820285] Call trace: > > [ 908.824785] __switch_to+0x68/0x90 > > [ 908.837661] 0xfffffe00603afd90 > > [ 908.844119] 0xfffffe00603afd90 > > [ 908.850091] 0xfffffe00603afd90 > > [ 908.854285] 0xfffffe00603afd90 > > [ 908.863538] 0xfffffe00603afd90 > > [ 908.865523] 0xfffffe00603afd90 > > > > The machine just locked up and kept on printing the same line over and > > over again. This patch fixes it. > > > > Signed-off-by: Mikulas Patocka > > Cc: stable at vger.kernel.org > > Given this can only occur when there's a corrupted stack (where a frame > record points to itself), I'm not sure this requires a cc stable. > > > Index: linux-2.6/arch/arm64/kernel/stacktrace.c > > =================================================================== > > --- linux-2.6.orig/arch/arm64/kernel/stacktrace.c > > +++ linux-2.6/arch/arm64/kernel/stacktrace.c > > @@ -56,6 +56,9 @@ int notrace unwind_frame(struct task_str > > frame->fp = READ_ONCE_NOCHECK(*(unsigned long *)(fp)); > > frame->pc = READ_ONCE_NOCHECK(*(unsigned long *)(fp + 8)); > > > > + if (frame->fp <= fp) > > + return -EINVAL; > > + > > Dave Martin had a series [1] which addressed this along with a number of > other cases where stack traces might not terminate. > > Dave, do you plan to respin that? I'd be interested in an update on that; we clearly should be fixing this in one way or another. Mikulus -- would you be able to test and/or review it, please? Will