From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752033Ab2LSXMt (ORCPT ); Wed, 19 Dec 2012 18:12:49 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:44632 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751948Ab2LSXMo (ORCPT ); Wed, 19 Dec 2012 18:12:44 -0500 Date: Wed, 19 Dec 2012 15:12:43 -0800 From: Andrew Morton To: "Dae S. Kim" Cc: arnd@arndb.de, gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] char/misc.c: misc_register: Do not loop on misc_list unconditionally Message-Id: <20121219151243.9f8882c8.akpm@linux-foundation.org> In-Reply-To: <20121217222638.GA3747@Delta> References: <20121217222638.GA3747@Delta> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 17 Dec 2012 23:26:38 +0100 "Dae S. Kim" wrote: > If the minor number is assigned dynamically, there is no need to > search for misc->minor in misc_list, since misc->minor == > MISC_DYNAMIC_MINOR. > > ... > > --- a/drivers/char/misc.c > +++ b/drivers/char/misc.c > @@ -190,12 +190,6 @@ int misc_register(struct miscdevice * misc) > INIT_LIST_HEAD(&misc->list); > > mutex_lock(&misc_mtx); > - list_for_each_entry(c, &misc_list, list) { > - if (c->minor == misc->minor) { > - mutex_unlock(&misc_mtx); > - return -EBUSY; > - } > - } > > if (misc->minor == MISC_DYNAMIC_MINOR) { > int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS); > @@ -205,6 +199,13 @@ int misc_register(struct miscdevice * misc) > } > misc->minor = DYNAMIC_MINORS - i - 1; > set_bit(i, misc_minors); > + } else { > + list_for_each_entry(c, &misc_list, list) { > + if (c->minor == misc->minor) { > + mutex_unlock(&misc_mtx); > + return -EBUSY; > + } > + } > } > Looks OK. It permits this: From: Andrew Morton Subject: drivers-char-miscc-misc_register-do-not-loop-on-misc_list-unconditionally-fix reduce scope of local `c' Cc: "Dae S. Kim" Cc: Arnd Bergmann Cc: Dae S. Kim Cc: Greg KH Signed-off-by: Andrew Morton --- drivers/char/misc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff -puN drivers/char/misc.c~drivers-char-miscc-misc_register-do-not-loop-on-misc_list-unconditionally-fix drivers/char/misc.c --- a/drivers/char/misc.c~drivers-char-miscc-misc_register-do-not-loop-on-misc_list-unconditionally-fix +++ a/drivers/char/misc.c @@ -183,7 +183,6 @@ static const struct file_operations misc int misc_register(struct miscdevice * misc) { - struct miscdevice *c; dev_t dev; int err = 0; @@ -200,6 +199,8 @@ int misc_register(struct miscdevice * mi misc->minor = DYNAMIC_MINORS - i - 1; set_bit(i, misc_minors); } else { + struct miscdevice *c; + list_for_each_entry(c, &misc_list, list) { if (c->minor == misc->minor) { mutex_unlock(&misc_mtx); _