linux-kernel - Re: stack unwinder warning.

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Date:   Fri, 6 Jan 2017 00:09:47 -0500
From:   Dave Jones <davej@...emonkey.org.uk>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: stack unwinder warning.

On Thu, Jan 05, 2017 at 11:02:14AM -0600, Josh Poimboeuf wrote:
 > On Thu, Jan 05, 2017 at 08:52:49AM -0600, Josh Poimboeuf wrote:
 > > On Tue, Dec 27, 2016 at 02:00:30PM -0500, Dave Jones wrote:
 > > > I'm not sure what to make of this. Josh ?  (4.10-rc1)
 > > > 
 > > > WARNING: kernel stack frame pointer at ffffc900003e7858 in trinity-c6:29122 has bad value ffffffff82103a80
 > > > unwind stack type:0 next_sp:          (null) mask:2 graph_idx:0
 > > > ffffc900003e7808: ffffffff811a02e5 (ring_buffer_lock_reserve+0x1d5/0x580)
 > > > ffffc900003e7810: ffffffff8119adc3 (rb_commit+0x93/0x350)
 > > > ffffc900003e7818: ffffffff811b31d4 (function_trace_call+0x104/0x1f0)
 > > > ffffc900003e7820: ffff8804f10ec000 (0xffff8804f10ec000)
 > > > ffffc900003e7828: 0000000000000000 ...
 > > > ffffc900003e7830: ffffffff8119b3ae (ring_buffer_unlock_commit+0x8e/0x120)
 > > > ffffc900003e7838: 0000000000000001 (0x1)
 > > > ffffc900003e7840: ffffea0002854e00 (0xffffea0002854e00)
 > > > ffffc900003e7848: 000000000000000a (0xa)
 > > > ffffc900003e7850: ffffea0002854ec0 (0xffffea0002854ec0)
 > > > ffffc900003e7858: ffffea000287c480 (0xffffea000287c480)
 > > 
 > > The value reported by the warning contradicts the value reported by the
 > > dump.  So this seems to have been caused by dumping the stack of a task
 > > which is running on another CPU.  There are still some places in the
 > > code where that's possible.  So I'm going to need to remove these
 > > unwinder warnings for now.
 > 
 > I'll be submitting the following patch soon, which I think should
 > silence the warning.  If the warning is recreatable, would you mind
 > testing it?

I didn't wait long enough..

WARNING: kernel stack frame pointer at ffffc90001443f30 in kworker/u8:8:30468 has bad value           (null)
unwind stack type:0 next_sp:          (null) mask:6 graph_idx:0
ffffc90001443d88: d0d0d0d0d0d0d0d0 (0xd0d0d0d0d0d0d0d0)
ffffc90001443d90: ffffffff81e5c420 (ftrace_trace_arrays+0x10/0x10)
ffffc90001443d98: d0d0d0d0d0d0d0d0 (0xd0d0d0d0d0d0d0d0)
ffffc90001443da0: ffff880253ff0848 (0xffff880253ff0848)
ffffc90001443da8: ffffc90001443e68 (0xffffc90001443e68)
ffffc90001443db0: ffffffff810a1430 (umh_complete+0x40/0x40)
ffffc90001443db8: 00000000000002a0 (0x2a0)
ffffc90001443dc0: 0000000000000001 (0x1)
ffffc90001443dc8: 0000000000000000 ...
ffffc90001443dd0: 0000000000000001 (0x1)
ffffc90001443dd8: 0000000000000001 (0x1)
ffffc90001443de0: 0000000000000000 ...
ffffc90001443de8: ffffffff81e5bcc0 (fgraph_sleep_time+0x20/0x20)
ffffc90001443df0: ffffffff818cb022 (ret_from_fork+0x22/0x30)
ffffc90001443df8: ffffffff810a1430 (umh_complete+0x40/0x40)
ffffc90001443e00: ffffffffffffff10 (0xffffffffffffff10)
ffffc90001443e08: ffffffff8117140c (function_trace_call+0x1c/0x190)
ffffc90001443e10: 0000000000000010 (0x10)
ffffc90001443e18: 0000000000000292 (0x292)
ffffc90001443e20: ffffc90001443e38 (0xffffc90001443e38)
ffffc90001443e28: 0000000000000000 ...
ffffc90001443e30: 0000000000000020 (0x20)
ffffc90001443e38: ffff8804f254a468 (0xffff8804f254a468)
ffffc90001443e40: ffffffff810a1430 (umh_complete+0x40/0x40)
ffffc90001443e48: ffff880253ff0848 (0xffff880253ff0848)
ffffc90001443e50: d0d0d0d0d0d0d0d0 (0xd0d0d0d0d0d0d0d0)
ffffc90001443e58: d0d0d0d0d0d0d0d0 (0xd0d0d0d0d0d0d0d0)
ffffc90001443e60: d0d0d0d0d0d0d0d0 (0xd0d0d0d0d0d0d0d0)
ffffc90001443e68: ffffc90001443f20 (0xffffc90001443f20)
ffffc90001443e70: ffffffffa0333077 (0xffffffffa0333077)
ffffc90001443e78: ffffc90001443ee0 (0xffffc90001443ee0)
ffffc90001443e80: 0000000000000086 (0x86)
ffffc90001443e88: ffffffff810b4618 (finish_task_switch+0x78/0x280)
ffffc90001443e90: ffff8804f2549c00 (0xffff8804f2549c00)
ffffc90001443e98: 0000000000000000 ...
ffffc90001443ea0: ffff880507bd8780 (0xffff880507bd8780)
ffffc90001443ea8: ffff880507bd8780 (0xffff880507bd8780)
ffffc90001443eb0: ffff8803211b5380 (0xffff8803211b5380)
ffffc90001443eb8: 0000000000000000 ...
ffffc90001443ec0: 0000000000000001 (0x1)
ffffc90001443ec8: 0000000080000000 (0x80000000)
ffffc90001443ed0: 0000000000000001 (0x1)
ffffc90001443ed8: 0000000080000001 (0x80000001)
ffffc90001443ee0: 0000000000000000 ...
ffffc90001443ee8: ffff880253ff0848 (0xffff880253ff0848)
ffffc90001443ef0: ffffffff810b4618 (finish_task_switch+0x78/0x280)
ffffc90001443ef8: ffffffff810a1435 (call_usermodehelper_exec_async+0x5/0x140)
ffffc90001443f00: ffff8803211b6a00 (0xffff8803211b6a00)
ffffc90001443f08: ffffffff810a1430 (umh_complete+0x40/0x40)
ffffc90001443f10: ffff880253ff0848 (0xffff880253ff0848)
ffffc90001443f18: d0d0d0d0d0d0d0d0 (0xd0d0d0d0d0d0d0d0)
ffffc90001443f20: ffffc90001443f30 (0xffffc90001443f30)
ffffc90001443f28: ffffffff810a1435 (call_usermodehelper_exec_async+0x5/0x140)
ffffc90001443f30: 0000000000000000 ...
ffffc90001443f38: ffffffff818cb022 (ret_from_fork+0x22/0x30)
ffffc90001443f40: 0000000000000000 ...
ffffc90001443f48: ffffffff810a1435 (call_usermodehelper_exec_async+0x5/0x140)
ffffc90001443f50: ffffffff818cb022 (ret_from_fork+0x22/0x30)
ffffc90001443f58: 0000000000000000 ...