linux-kernel - Re: 2.6.18-rc3-g3b445eea BUG: warning at /usr/src/linux-git/kernel/cpu.c:51/unlock_cpu

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Date:	Mon, 7 Aug 2006 03:26:38 +0200
From:	Andi Kleen <ak@....de>
To:	Andrew Morton <akpm@...l.org>
Cc:	Michal Piotrowski <michal.k.k.piotrowski@...il.com>,
	davej@...hat.com, torvalds@...l.org, linux-kernel@...r.kernel.org,
	Jan Beulich <jbeulich@...ell.com>
Subject: Re: 2.6.18-rc3-g3b445eea BUG: warning at /usr/src/linux-git/kernel/cpu.c:51/unlock_cpu_hotplug()

> >  [<c0171577>] vfs_write+0xcd/0x179
> >  [<c0171c20>] sys_write+0x3b/0x71
> >  [<c010318d>] sysenter_past_esp+0x56/0x8d
> This "unwinder stuck" thing seems to be very common.

Yes, there are still a lot of bugs in the unwind annotation
unfortunately.

We're also slowly discovering that some things we do cannot
even be expressed in CFI, so some code has to change.

> 
> It's a false-positive in this case - the backtrace was complete.  It would
> be good if we could make the did-we-get-stuck detector a bit smarter.  Even
> special-casing "sysenter_past_esp" would stop a lot of this..

Actually it's not completely false in this case -- it should
have reached user mode and stopped there, but for some reason
I didn't and already stopped still in the kernel.

Most likely the CFI annotation for that sysenter path is not complete.

It's on my todo list to investigate but I still hope Jan does it first ;-)

-Andi


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