Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263221AbTLADxn (ORCPT ); Sun, 30 Nov 2003 22:53:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263258AbTLADxn (ORCPT ); Sun, 30 Nov 2003 22:53:43 -0500 Received: from svr-ganmtc-appserv-mgmt.ncf.coxexpress.com ([24.136.46.5]:24070 "EHLO svr-ganmtc-appserv-mgmt.ncf.coxexpress.com") by vger.kernel.org with ESMTP id S263221AbTLADxm (ORCPT ); Sun, 30 Nov 2003 22:53:42 -0500 Subject: Re: question about preempt_disable() From: Rob Love To: Matthias Urlichs Cc: linux-kernel@vger.kernel.org In-Reply-To: References: <000d01c3b6dd$30ab34a0$8a04a943@bananacabana> Content-Type: text/plain Message-Id: <1070250821.1158.45.camel@localhost> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.5 (1.4.5-8) Date: Sun, 30 Nov 2003 22:53:41 -0500 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 2003-11-30 at 12:39, Matthias Urlichs wrote: > You need to prevent deadlocks. Imagine process A grabbing a spinlock, then > getting preempted. Process B now sits there and waits on the spinlock. > Forward progress may or may not happen when the scheduler preempts B and > restarts A, some indeterminate time later. Further, on uniprocessor systems, we don't have deadlocks so it is the preempt_disable() that actually ensures concurrency is prevented in the critical region. Rob Love - 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/