linux-kernel - Re: [PATCH 3/4 V2] futex: free_pi_state outside of hb->lock sections

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Date:	Sat, 10 Jul 2010 07:41:22 -0700
From:	Darren Hart <dvhltc@...ibm.com>
To:	rostedt@...dmis.org
CC:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Eric Dumazet <eric.dumazet@...il.com>,
	John Kacur <jkacur@...hat.com>, Mike Galbraith <efault@....de>,
	linux-rt-users@...r.kernel.org
Subject: Re: [PATCH 3/4 V2] futex: free_pi_state outside of hb->lock sections

On 07/09/2010 05:32 PM, Steven Rostedt wrote:
> On Fri, 2010-07-09 at 15:55 -0700, Darren Hart wrote:
>> Apologies, mangled a rebase and this patch had bits of 4/4 in it.
>> Corrected below:
>>
>>
>> > From f40b8e684df6ed2b1ba9167cad3922ab43f4a717 Mon Sep 17 00:00:00 2001
>> From: Darren Hart<dvhltc@...ibm.com>
>> Date: Fri, 9 Jul 2010 17:07:10 -0400
>> Subject: [PATCH 3/4 V2] futex: free_pi_state outside of hb->lock sections
>>
>> free_pi_state() calls kfree() and might sleep. To prepare for raw hb->locks,
>> get the calls to free_pi_state() out of the hb->lock() sections.
>>
>> Signed-off-by: Darren Hart<dvhltc@...ibm.com>
>> Cc: Thomas Gleixner<tglx@...utronix.de>
>> Cc: Peter Zijlstra<peterz@...radead.org>
>> Cc: Ingo Molnar<mingo@...e.hu>
>> Cc: Eric Dumazet<eric.dumazet@...il.com>
>> Cc: John Kacur<jkacur@...hat.com>
>> Cc: Steven Rostedt<rostedt@...dmis.org>
>> Cc: Mike Galbraith<efault@....de>
>> ---
>>   kernel/futex.c |    8 +++++---
>>   1 files changed, 5 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/futex.c b/kernel/futex.c
>> index a6cec32..2cd58a2 100644
>> --- a/kernel/futex.c
>> +++ b/kernel/futex.c
>> @@ -1339,7 +1339,6 @@ retry_private:
>
> This is why I always add a space before labels. I have no idea what
> function this was in.
>
>>   			} else if (ret) {
>>   				/* -EDEADLK */
>>   				this->pi_state = NULL;
>> -				free_pi_state(pi_state);
>
> Where do we free the pi state here?

Near the end after goto out_unlock which falls through to the out: 
label. In this case I didn't move it, it just wasn't necessary.

out:
	if (pi_state != NULL)
		free_pi_state(pi_state);


--
Darren Hart
IBM Linux Technology Center
Real-Time Linux Team
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