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From: Akinobu Mita <akinobu.mita@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: akpm@linux-foundation.org
Subject: [PATCH 2/5] idr: use call_once()
Date: Tue, 11 Mar 2008 00:00:27 +0900	[thread overview]
Message-ID: <20080310150026.GA6407@APFDCB5C> (raw)
In-Reply-To: <20080310145704.GA6396@APFDCB5C>

idr_layer_cache is created when idr_init() is called first time by someone.

This patch makes the idr_layer_cache initialization to use call_once().

This conversion prevents an unlikely race condition when two idr_init()
callers attempt to create idr_layer_cache simultaneously.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
---
 lib/idr.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

Index: 2.6-rc/lib/idr.c
===================================================================
--- 2.6-rc.orig/lib/idr.c
+++ 2.6-rc/lib/idr.c
@@ -28,6 +28,7 @@
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/module.h>
+#include <linux/once.h>
 #endif
 #include <linux/err.h>
 #include <linux/string.h>
@@ -585,12 +586,12 @@ static void idr_cache_ctor(struct kmem_c
 	memset(idr_layer, 0, sizeof(struct idr_layer));
 }
 
-static  int init_id_cache(void)
+static int init_id_cache(void)
 {
-	if (!idr_layer_cache)
-		idr_layer_cache = kmem_cache_create("idr_layer_cache",
+	idr_layer_cache = kmem_cache_create("idr_layer_cache",
 			sizeof(struct idr_layer), 0, 0, idr_cache_ctor);
-	return 0;
+
+	return !idr_layer_cache ? -ENOMEM : 0;
 }
 
 /**
@@ -602,7 +603,9 @@ static  int init_id_cache(void)
  */
 void idr_init(struct idr *idp)
 {
-	init_id_cache();
+	static DEFINE_ONCE(once);
+
+	call_once(&once, init_id_cache);
 	memset(idp, 0, sizeof(struct idr));
 	spin_lock_init(&idp->lock);
 }

  reply	other threads:[~2008-03-10 15:08 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-03-10 14:57 [PATCH 1/5] lib: introduce call_once() Akinobu Mita
2008-03-10 15:00 ` Akinobu Mita [this message]
2008-03-10 15:01   ` [PATCH 3/5] hugetlbfs: use call_once() Akinobu Mita
2008-03-10 15:03     ` [PATCH 4/5] shmem: " Akinobu Mita
2008-03-10 15:05       ` [PATCH 5/5] tiny-shmem: " Akinobu Mita
2008-03-10 22:15       ` [PATCH 4/5] shmem: " Hugh Dickins
2008-03-11 12:29         ` Akinobu Mita
2008-03-11 13:41           ` Hugh Dickins
2008-03-10 15:29 ` [PATCH 1/5] lib: introduce call_once() Joe Perches
2008-03-11 12:17   ` Akinobu Mita
2008-03-11  3:48 ` Andrew Morton
2008-03-11  4:10   ` Nick Piggin
2008-03-11  4:21     ` Andrew Morton
2008-03-11 12:27       ` Akinobu Mita
2008-03-11 17:35         ` Andrew Morton
2008-03-11 18:56           ` Joe Perches
2008-03-11 19:11             ` Andrew Morton
2008-03-15  4:01           ` Akinobu Mita
2008-03-11 12:41 ` Nick Piggin

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