linux-kernel - [PATCH 2/2] arch/sh/mm: Eliminate a double lock

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Message-ID: <Pine.LNX.4.64.1006201324360.4366@ask.diku.dk>
Date:	Sun, 20 Jun 2010 13:24:54 +0200 (CEST)
From:	Julia Lawall <julia@...u.dk>
To:	Paul Mundt <lethal@...ux-sh.org>, linux-sh@...r.kernel.org,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: [PATCH 2/2] arch/sh/mm: Eliminate a double lock

From: Julia Lawall <julia@...u.dk>

The function begins and ends with a read_lock.  The latter is changed to a
read_unlock.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

// <smpl>
@locked@
expression E1;
position p;
@@

read_lock(E1@p,...);

@r exists@
expression x <= locked.E1;
expression locked.E1;
expression E2;
identifier lock;
position locked.p,p1,p2;
@@

*lock@p1 (E1@p,...);
... when != E1
    when != \(x = E2\|&x\)
*lock@p2 (E1,...);
// </smpl>

Signed-off-by: Julia Lawall <julia@...u.dk>

---
Not tested

 arch/sh/mm/pmb.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/sh/mm/pmb.c b/arch/sh/mm/pmb.c
index 18623ba..6379091 100644
--- a/arch/sh/mm/pmb.c
+++ b/arch/sh/mm/pmb.c
@@ -770,7 +770,7 @@ static void __init pmb_resize(void)
 		spin_unlock_irqrestore(&pmbe->lock, flags);
 	}
 
-	read_lock(&pmb_rwlock);
+	read_unlock(&pmb_rwlock);
 }
 #endif
 
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