From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965197AbWLUKVs (ORCPT ); Thu, 21 Dec 2006 05:21:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S965195AbWLUKVs (ORCPT ); Thu, 21 Dec 2006 05:21:48 -0500 Received: from aa014msr.fastwebnet.it ([85.18.95.74]:45732 "EHLO aa014msr.fastwebnet.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S965197AbWLUKVs (ORCPT ); Thu, 21 Dec 2006 05:21:48 -0500 Date: Thu, 21 Dec 2006 11:20:00 +0100 From: Paolo Ornati To: "Sorin Manolache" Cc: linux-kernel@vger.kernel.org Subject: Re: newbie questions about while (1) in kernel mode and spinlocks Message-ID: <20061221112000.67722190@localhost> In-Reply-To: <20170a030612210141y6578602eo525e6df5f324747d@mail.gmail.com> References: <20170a030612210141y6578602eo525e6df5f324747d@mail.gmail.com> X-Mailer: Sylpheed-Claws 2.4.0 (GTK+ 2.10.6; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 21 Dec 2006 10:41:44 +0100 "Sorin Manolache" wrote: > spin_lock(&lck); > down(&sem); /* I know that one shouldn't sleep when holding a lock */ > /* but I want to understand why */ I suppose because the lock is held for an indefinite amount of time and any other process that try to get that lock will "spin" and burn CPU without doing anything useful (locking the process in kernel mode and preventing the execution of other processes on that CPU if there isn't any type of PREEMPTION). :) spin_lock is a "while(1) {...}" thing... -- Paolo Ornati Linux 2.6.20-rc1-g99f5e971 on x86_64