linux-kernel - Re: [PATCH 0/3] lockdep: liblockdep: Prevent chain

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Date:	Tue, 16 Feb 2016 11:38:26 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Alfredo Alvarez Fernandez <alfredoalvarezfernandez@...il.com>,
	mingo@...hat.com, peterz@...radead.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/3] lockdep: liblockdep: Prevent chain_key collisions

On 02/10/2016 06:33 PM, Alfredo Alvarez Fernandez wrote:
> This patch series prevents possible collisions in the chain_key
> hashing macro iterate_chain_key(key1, key2) that can lead to lockdep 
> not detecting very simple deadlocks such as AA or ABBA.
> 
> The problem only affects the first allocated lock classes. That could 
> explain why it was not seen while running lockdep's test suite, since
> by the time the test suite runs there are already registered lock 
> classes and the indexes allocated for the lock classes under test are
> high enough to avoid collisions.
> 
> The patch series also extends the tools/liblockdep test suite with 
> tests covering the offending cases.
> 
> I came across the problem while testing a simple AA deadlock scenario
> in userspace using a pthread_mutex and tools/liblockdep. In that 
> context it is fairly easy to have a clean and deterministic initial 
> state where the problem can be reproduced.
> 
> The proposed solution was tested with the newly introduced tests and
> also with lockdep's test suite:
>  [    0.000000] Good, all 253 testcases passed! |

Thanks Alfredo, I'll grab the first two.

Peter/Ingo, will you take the lockdep one or do you want it to go through
my tree?


Thanks,
Sasha