linux-kernel - Re: stack unwinder warning.

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Date:   Thu, 5 Jan 2017 08:52:49 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Dave Jones <davej@...emonkey.org.uk>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: stack unwinder warning.

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.

-- 
Josh