linux-kernel - Re: [PATCH] kernel/futex.c: notice the return value after rt_mutex_finish_proxy

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Date:	Wed, 21 Aug 2013 11:48:10 +0800
From:	Chen Gang <gang.chen@...anux.com>
To:	Darren Hart <dvhart@...ux.intel.com>
CC:	Thomas Gleixner <tglx@...utronix.de>, ccross@...roid.com,
	Mel Gorman <mgorman@...e.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kernel/futex.c: notice the return value after rt_mutex_finish_proxy_lock()
 fails

On 08/21/2013 12:19 AM, Darren Hart wrote:
> HopingOn Tue, 2013-08-20 at 11:07 +0800, Chen Gang wrote:
> 
> 
> Hi Chen,
> 
>> rt_mutex_finish_proxy_lock() can return failure code (e.g. -EINTR,
>> -ETIMEDOUT).
>>
>> Original implementation has already noticed about it, but not check it
>> before next work.
>>
>> Also let coments within 80 columns to pass "./scripts/checkpatch.pl".
>>
>>
>> Signed-off-by: Chen Gang <gang.chen@...anux.com>
>> ---
>>  kernel/futex.c |   30 ++++++++++++++++--------------
>>  1 files changed, 16 insertions(+), 14 deletions(-)
>>
>> diff --git a/kernel/futex.c b/kernel/futex.c
>> index c3a1a55..1a94e7d 100644
>> --- a/kernel/futex.c
>> +++ b/kernel/futex.c
>> @@ -2373,21 +2373,23 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
>>  		ret = rt_mutex_finish_proxy_lock(pi_mutex, to, &rt_waiter, 1);
>>  		debug_rt_mutex_free_waiter(&rt_waiter);
>>  
>> -		spin_lock(q.lock_ptr);
>> -		/*
>> -		 * Fixup the pi_state owner and possibly acquire the lock if we
>> -		 * haven't already.
>> -		 */
>> -		res = fixup_owner(uaddr2, &q, !ret);
> 
> 
> This call catches a corner case which appears to be skipped now. Or am I
> missing how you accounted for that?
> 
> 

Pardon ?

Hmm... this patch lets related code block in "if(!ret) {...}", should
not remove any code.

Please help check again for whether what I have done is correct or not.

Thanks.

>> -		/*
>> -		 * If fixup_owner() returned an error, proprogate that.  If it
>> -		 * acquired the lock, clear -ETIMEDOUT or -EINTR.
>> -		 */
>> -		if (res)
>> -			ret = (res < 0) ? res : 0;
>> +		if (!ret) {
>> +			spin_lock(q.lock_ptr);
>> +			/*
>> +			 * Fixup the pi_state owner and possibly acquire the
>> +			 * lock if we haven't already.
>> +			 */
>> +			res = fixup_owner(uaddr2, &q, !ret);
>> +			/*
>> +			 * If fixup_owner() returned an error, proprogate that.
>> +			 * If it acquired the lock, clear -ETIMEDOUT or -EINTR.
>> +			 */
>> +			if (res)
>> +				ret = (res < 0) ? res : 0;
>>  
>> -		/* Unqueue and drop the lock. */
>> -		unqueue_me_pi(&q);
>> +			/* Unqueue and drop the lock. */
>> +			unqueue_me_pi(&q);
>> +		}
>>  	}
>>  
>>  	/*
> 
> Thanks,
> 


-- 
Chen Gang
--
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