From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932183AbYEUIUc (ORCPT ); Wed, 21 May 2008 04:20:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753559AbYEUIUM (ORCPT ); Wed, 21 May 2008 04:20:12 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:37321 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751020AbYEUIUJ (ORCPT ); Wed, 21 May 2008 04:20:09 -0400 Date: Wed, 21 May 2008 01:19:26 -0700 From: Andrew Morton To: Christoph Hellwig Cc: Rusty Russell , Linus Torvalds , linux-kernel@vger.kernel.org, Stephen Rothwell , Matthew Wilcox Subject: Re: [PATCH] Introduce down_nowait() Message-Id: <20080521011926.18bf8e81.akpm@linux-foundation.org> In-Reply-To: <20080521080452.GA1305@infradead.org> References: <200805211600.16415.rusty@rustcorp.com.au> <20080520232903.6756b1c1.akpm@linux-foundation.org> <20080521080452.GA1305@infradead.org> X-Mailer: Sylpheed 2.4.8 (GTK+ 2.12.5; x86_64-redhat-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 Wed, 21 May 2008 04:04:53 -0400 Christoph Hellwig wrote: > On Tue, May 20, 2008 at 11:29:03PM -0700, Andrew Morton wrote: > > Actually, I don't thing down_nowait() is a terribly good name, because it > > doesn't tell the reader anything about what to expect from the return > > value. Does a non-zero return mean that down_wait() acquired the lock, > > or does it not? Something like down_try() would be better, because if > > it returns 1 we can say "ah, the trying succeeded". > > Actually, it does, No it doesn't. If anything, a "true" return from something called "down_nowait()" means "I didn't wait!". Or something. > and the kerneldoc comment explains it in every detail > for those who need to read it up. Shouldn't be necessary to look it up. By that argument we could call it eat_at_joes() and sell the advertising space. > Then again semaphores and on their > way out, and I really hate the kind of churn this thing introduces at > this moment. Please let all the semaphore to completion/mutex/other > construct change settle for a while, and with a little chance this gem > will just go away entirely. Well, we can walk and chew gum at the same time. The number of down_trylocks in rc3 is 51 and the number of down_trylocks and down_nowaits in -mm is 47. So progress is pretty glacial. ./kernel/semaphore.c ./kernel/mutex.c ./include/linux/semaphore.h Anyway, yes, I agree that the whole effort is a bit dubious and that the time could be better directed to semaphore eliminations.