linux-kernel - Re: futex question

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Message-ID: <4AC8CF32.8060108@anirban.org>
Date:	Sun, 04 Oct 2009 09:37:06 -0700
From:	Anirban Sinha <ani@...rban.org>
To:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	linux-kernel@...r.kernel.org, Darren Hart <dvhltc@...ibm.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Kaz Kylheku <kaz@...gmasystems.com>,
	Anirban Sinha <asinha@...gmasystems.com>
Subject: Re: futex question

>> 1) What caused you to instrument this path in the first place?  Were you
>> seeing some unexpected behavior?
>>
>> 2) I wonder why we would need to clear the robust list, but I don't see other
>> things like pi_blocked_on, etc. in execve being cleared.  I'm looking into
>> this now (perhaps we don't do the same cleanup, need to check).... have to get
>> on the plane...
> 
> Hmm, just setting the robust list pointer to NULL fixes the problem at
> hand, but I wonder whether we need to call exit_robust_list() as
> well. 

hmm. That is an interesting thought. But I wonder if acquiring a lock and then exec()ing in the critical section is a legal thing to do. It does not feel right. Currently, with or without my change, such a thing would indefinitely block other waiters on the same futex.  

Ani
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