linux-kernel - Re: [tip:sched/locking] sched: Add p->pi_lock to task_rq

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Date:	Sun, 05 Jun 2011 08:01:58 +0200
From:	Arne Jansen <lists@...-jansens.de>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, hpa@...or.com,
	linux-kernel@...r.kernel.org, efault@....de, npiggin@...nel.dk,
	akpm@...ux-foundation.org, frank.rowand@...sony.com,
	linux-tip-commits@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [tip:sched/locking] sched: Add p->pi_lock to task_rq_lock()

On 05.06.2011 00:08, Peter Zijlstra wrote:
> On Sun, 2011-06-05 at 06:29 +0900, Linus Torvalds wrote:
>> On Fri, Jun 3, 2011 at 10:05 PM, Arne Jansen<lists@...-jansens.de>  wrote:
>>>
>>> No change. Also git bisect quite clearly points to
>>> 0122ec5b02f766c and ab2515c4b98f7bc4, both are older than
>>> b1c43f82c5aa2654 mentioned in the other thread.
>>
>> Ok, I haven't heard anything further on this. Ingo? Peter?
>
> I'm a bit stumped, and not being able to reproduce at all :/

I'm willing to take any number of round trips to get to the true
nature of the bug. From the description I have a feeling that the
offending patch might just shift the timing slightly, so even if
the problem is gone for me, it might just be buried deeper.
I can also try to reproduce it on a second machine and give you
access to it, though this might take a few days.

>
>> We're getting to the point where we just need to revert the thing,
>> since I'm not getting the feeling that there are any fixes
>> forthcoming, and I'd like -rc2 to not have this kind of bisected bug.
>
> Agreed.
>
>> Ingo? Those two commits no longer revert cleanly, presumably due to
>> other changes in the area (but I didn't check). Can you do a patch to
>> do the reverts, and then you can try to re-do the thing later once you
>> figure out what's wrong.
>
> Yeah, that wants a whole lot of reverting, from the offending commit up
> to and including 317f394160e9beb97d19a84c39b7e5eb3d7815a8.
>
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