From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754138AbYCJPIe (ORCPT ); Mon, 10 Mar 2008 11:08:34 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751350AbYCJPIP (ORCPT ); Mon, 10 Mar 2008 11:08:15 -0400 Received: from el-out-1112.google.com ([209.85.162.180]:1730 "EHLO el-out-1112.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751055AbYCJPIO (ORCPT ); Mon, 10 Mar 2008 11:08:14 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version:content-type:content-disposition:in-reply-to:user-agent; b=qdeiAcyjID9RwyKE/sapytWrnkAZlwMtocAqv7Xleds/wulmGcNIKDPSlqVCBUwLaFvKmraoAhXZiM6rzPGsDwaUEgqPQkogmVAWcTucA/UJh8LRu5AYYbF2CW0RsKA8EVxKz11FVxdCXyl3riJnAOj5ZfcUt7P+4dS4O5dupio= Date: Tue, 11 Mar 2008 00:00:27 +0900 From: Akinobu Mita To: linux-kernel@vger.kernel.org Cc: akpm@linux-foundation.org Subject: [PATCH 2/5] idr: use call_once() Message-ID: <20080310150026.GA6407@APFDCB5C> References: <20080310145704.GA6396@APFDCB5C> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-2022-jp Content-Disposition: inline In-Reply-To: <20080310145704.GA6396@APFDCB5C> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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 #include #include +#include #endif #include #include @@ -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); }