linux-kernel - Re: stack unwinder warning.

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Date:   Thu, 5 Jan 2017 18:50:43 -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?

Ok, haven't seen anything fall out today while running with this, I'd
call it good. It usually showed up pretty quickly.

	Dave