linux-kernel - Re: [PATCH 09/11] liblockdep: support using LD

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Date:	Fri, 08 Feb 2013 18:55:54 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Jamie Iles <jamie.iles@...cle.com>
CC:	mingo@...nel.org, peterz@...radead.org, penberg@...nel.org,
	acme@...stprotocols.net, paulus@...ba.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 09/11] liblockdep: support using LD_PRELOAD

On 02/08/2013 05:43 AM, Jamie Iles wrote:
> On Thu, Feb 07, 2013 at 09:31:22AM -0500, Sasha Levin wrote:
>> On 02/07/2013 05:28 AM, Jamie Iles wrote:
>>>> +int pthread_rwlock_init(pthread_rwlock_t *rwlock,
>>>>> +			const pthread_rwlockattr_t *attr)
>>>>> +{
>>>>> +	if (ll_pthread_rwlock_init == NULL)
>>>>> +		init_preload();
>>> Why is this one special, doesn't init_preload being a constructor make 
>>> this redundant?
>>
>> I was testing it on different things, and stumbled on an interesting case:
>> when pthread_mutex was taken from the constructor of a different module.
>>
>> In that case, the other constructor would try to init the mutex and take
>> a lock, but we would segfault because we haven't resolved the pthread
>> symbols yet ourselves (since our constructor was yet to be called).
> 
> Okay, that makes sense, but shouldn't we do this for all of the lock 
> operations?  pthread locks can be statically initialized and they are 
> initializaed lazily on the first access so I think that this could 
> happen on any of the lock operations.

hmm... I've had it only in init() because I thought it doesn't make sense
to actually lock/unlock in constructor code, but yeah - better safe than
sorry.


Thanks,
Sasha

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