Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751355AbZL0VDc (ORCPT ); Sun, 27 Dec 2009 16:03:32 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751093AbZL0VDT (ORCPT ); Sun, 27 Dec 2009 16:03:19 -0500 Received: from one.firstfloor.org ([213.235.205.2]:43506 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751042AbZL0VDQ (ORCPT ); Sun, 27 Dec 2009 16:03:16 -0500 From: Andi Kleen References: <200912271003.631128760@firstfloor.org> In-Reply-To: <200912271003.631128760@firstfloor.org> To: stefani@seibold.net, linux-kernel@vger.kernel.org, akpm@osdl.org Subject: [PATCH] [2/6] kfifo: Make kfifo_in atomic Message-Id: <20091227210312.A60FCB17C3@basil.firstfloor.org> Date: Sun, 27 Dec 2009 22:03:12 +0100 (CET) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2013 Lines: 54 Right now kfifo_in allows copying in less than the input amount. This is unfortunately not a good idea on any record oriented users: if the size of the kfifo is not a multiple of the record (and that can easily happen due to the power-of-two requirement) then when the FIFO fills up partial records could be put in. Such a condition would be fatal for any record consumer who would get permanently desynchronized. In fact I doubt unless the input is a totally boundary less data stream I doubt anything could handle this. Change kfifo_in() to always put in everything or nothing. The return value is now always 0 or the full length. Signed-off-by: Andi Kleen --- kernel/kfifo.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-) Index: linux/kernel/kfifo.c =================================================================== --- linux.orig/kernel/kfifo.c +++ linux/kernel/kfifo.c @@ -228,9 +228,8 @@ EXPORT_SYMBOL(__kfifo_in_n); * @from: the data to be added. * @len: the length of the data to be added. * - * This function copies at most @len bytes from the @from buffer into - * the FIFO depending on the free space, and returns the number of - * bytes copied. + * This function copies @len bytes from the @from buffer into + * the FIFO and returns 0 if there is not enough space. * * Note that with only one concurrent reader and one concurrent * writer, you don't need extra locking to use these functions. @@ -238,8 +237,8 @@ EXPORT_SYMBOL(__kfifo_in_n); unsigned int kfifo_in(struct kfifo *fifo, const void *from, unsigned int len) { - len = min(kfifo_avail(fifo), len); - + if (kfifo_avail(fifo) < len) + return 0; __kfifo_in_data(fifo, from, len, 0); __kfifo_add_in(fifo, len); return len; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/