From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp2.linux-foundation.org ([207.189.120.14]:37369 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754489AbXJVUCn (ORCPT ); Mon, 22 Oct 2007 16:02:43 -0400 Date: Mon, 22 Oct 2007 13:02:23 -0700 From: Andrew Morton Subject: Re: [PATCH 1/2] irq_flags_t: intro and core annotations Message-Id: <20071022130223.f7d75c31.akpm@linux-foundation.org> In-Reply-To: References: <20071020235546.GB1825@martell.zuzino.mipt.ru> <20071022152912.GA841@linux-mips.org> <20071022112110.105b8e11.akpm@linux-foundation.org> <200710222110.34768.arnd@arndb.de> <20071022194714.GI27248@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org To: Linus Torvalds Cc: matthew@wil.cx, arnd@arndb.de, ralf@linux-mips.org, adobriyan@gmail.com, viro@ftp.linux.org.uk, viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org List-ID: On Mon, 22 Oct 2007 12:56:29 -0700 (PDT) Linus Torvalds wrote: > > > On Mon, 22 Oct 2007, Matthew Wilcox wrote: > > > > We certainly don't want to encourage people to blindly make those > > conversions ... and I've seen the results of encouraging kernel janitors > > to do things a certain way. > > There's another issue: the "irqsave/irqrestore" versions are much safer > than the plain "irq" versions, in case the caller already has interrupts > disabled. > > So anybody making the change not only would need to make the performance > argument, he'd better not be a janitor that blindly does the change > without thinking about all call-sites etc.. > It's almost always a bug to do spin_lock_irq() when local interrupts are disabled. However iirc when we've tried to add runtime debugging to catch that, it triggered false-positives which made the idea unworkable. I forget where. However what we could do is to add a new spin_lock_irq_tell_me_if_i_goofed() which would perform that runtime check.