linux-kernel - Re: [PATCH -v3] futex: fix reference leak

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Date:	Wed, 11 Feb 2009 16:56:42 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>,
	Catalin Marinas <catalin.marinas@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Darren Hart <dvhltc@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH -v3] futex: fix reference leak

On Wed, 2009-02-11 at 16:49 +0100, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > So you prefer this version?
> 
> yes, with s/out_unlock_put_key/err_unlock_put_key. That's the
> only error path that goes via the tail of the function, correct?

Right, but I think one can argue that most of the out* jumps are errors.

The only non-error return is the !unqueue_me() case.

Also, since there's only one user of out_unlock_put_key, we might also
do this:

---
Index: linux-2.6/kernel/futex.c
===================================================================
--- linux-2.6.orig/kernel/futex.c
+++ linux-2.6/kernel/futex.c
@@ -1220,8 +1220,10 @@ retry:
 		goto out;
 	}
 	ret = -EWOULDBLOCK;
-	if (uval != val)
-		goto out_unlock_put_key;
+	if (uval != val) {
+		queue_unlock(&q, hb);
+		goto out_put_key;
+	}
 
 	/* Only actually queue if *uaddr contained val.  */
 	queue_me(&q, hb);
@@ -1319,10 +1321,6 @@ out_put_key:
 	put_futex_key(fshared, &q.key);
 out:
 	return ret;
-
-out_unlock_put_key:
-	queue_unlock(&q, hb);
-	goto out_put_key;
 }
 
 

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