Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753398Ab0L2O6Q (ORCPT ); Wed, 29 Dec 2010 09:58:16 -0500 Received: from wolverine01.qualcomm.com ([199.106.114.254]:44290 "EHLO wolverine01.qualcomm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753330Ab0L2O6O (ORCPT ); Wed, 29 Dec 2010 09:58:14 -0500 X-IronPort-AV: E=McAfee;i="5400,1158,6210"; a="68640658" Subject: Re: [PATCH v0] add nano semaphore in kernel From: Daniel Walker To: Hillf Danton Cc: Arnd Bergmann , linux-kernel@vger.kernel.org, Mike Christie In-Reply-To: References: <201012272215.52642.arnd@arndb.de> <1293551490.24601.10.camel@m0nster> <201012291247.27663.arnd@arndb.de> Content-Type: text/plain; charset="UTF-8" Date: Wed, 29 Dec 2010 06:58:07 -0800 Message-ID: <1293634687.4128.10.camel@m0nster> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1340 Lines: 33 On Wed, 2010-12-29 at 22:42 +0800, Hillf Danton wrote: > On Wed, Dec 29, 2010 at 7:47 PM, Arnd Bergmann wrote: > > On Tuesday 28 December 2010 16:51:30 Daniel Walker wrote: > >> We for sure don't want new semaphores, or new semaphore usage in the > >> kernel .. > > Would you please, Daniel, explain why there are so my file systems under > the fs directory? Would you think the ext file system is better than others? > > And why there are in kernel spin lock, read/write lock, mutex, rw_mutex, > rtmutx, and semaphore, timer and hrtimer? > > Could timer be removed tonight? The problem with semaphores is that people use them in ways that are not very nice, and not very efficient.. Since they are so flexible they can be used in all sorts of ways, many of which are not clean. This is why, if you read the kernel history, most semaphore have been removed from the kernel and replaced with much nicer and cleaner mutexes. Daniel -- Sent by an consultant of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- 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/