linux-kernel - Re: [BUG 3.3-rc2] spinlock trylock failure on UP on CPU#0

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Message-ID: <CANejiEWBdL4G3qt4=qjzakkokt1xbmcRXFS15EFt3bnSsvkCMA@mail.gmail.com>
Date:	Mon, 6 Feb 2012 09:25:01 +0800
From:	Shaohua Li <shaohua.li@...el.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Knut Petersen <Knut_Petersen@...nline.de>,
	Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [BUG 3.3-rc2] spinlock trylock failure on UP on CPU#0

2012/2/6 Linus Torvalds <torvalds@...ux-foundation.org>:
> Ok, interesting. You're triggering the issue because you have a UP
> build with the spinlock debugging code enabled.
>
> On Sun, Feb 5, 2012 at 12:57 PM, Knut Petersen
> <Knut_Petersen@...nline.de> wrote:
>> Booting  23783f817bceedd6d4e549385e3f400ea64059e5 I get the following trace
>> an AOpen i915GMm-hfs with Pentium-M Dothan:
>
> This is probably the same "technically legal" code that LOCKDEP also
> is unhappy about - the nested fast path release. We do a trylock on
> the queue lock while we already are holding the queue lock
> recursively.
>
> Jens, Tejun - the crazy-ass games that this code is playing is clearly
> messing not just with lockdep, it's messing with some very reasonable
> spinlock sanity checks on UP (which just boil down to "a spinlock
> should never have contention on UP")
>
> Any chance of sanitizing this all?
I just sent out a debug patch, please try:
http://marc.info/?l=linux-kernel&m=132849146702770&w=2
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