From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750926AbVLOStx (ORCPT ); Thu, 15 Dec 2005 13:49:53 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750924AbVLOStw (ORCPT ); Thu, 15 Dec 2005 13:49:52 -0500 Received: from stat9.steeleye.com ([209.192.50.41]:27587 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S1750911AbVLOStw (ORCPT ); Thu, 15 Dec 2005 13:49:52 -0500 Subject: RE: [PATCH 1/19] MUTEX: Introduce simple mutex implementation From: James Bottomley To: "Luck, Tony" Cc: dhowells@redhat.com, Andrew Morton , Mark Lord , tglx@linutronix.de, alan@lxorguk.ukuu.org.uk, pj@sgi.com, mingo@elte.hu, hch@infradead.org, torvalds@osdl.org, arjan@infradead.org, matthew@wil.cx, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org In-Reply-To: References: Content-Type: text/plain Date: Thu, 15 Dec 2005 10:48:48 -0800 Message-Id: <1134672528.3751.0.camel@mulgrave> Mime-Version: 1.0 X-Mailer: Evolution 2.2.3 (2.2.3-2.fc4) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2005-12-15 at 09:45 -0800, Luck, Tony wrote: > There was a USENIX paper a couple of decades ago that described how > to do a fast s/w disable of interrupts on machines where really disabling > interrupts was expensive. The rough gist was that the spl[1-7]() > functions would just set a flag in memory to hold the desired interrupt > mask. If an interrupt actually occurred when it was s/w blocked, the > handler would set a pending flag, and just rfi with interrupts disabled. > Then the splx() code checked to see whether there was a pending interrupt > and dealt with it if there was. Would you believe that that paper was written about the NCR Voyager architecture (The VIC is very expensive for interrupt disables) and that the current Linux Voyager Subarchitecture still makes partial use of the scheme. James