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

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Date:	Tue, 20 Aug 2013 09:19:49 -0700
From:	Darren Hart <dvhart@...ux.intel.com>
To:	Chen Gang <gang.chen@...anux.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

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?


> -		/*
> -		 * 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,

-- 
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel


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