From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 6358 invoked by alias); 14 Mar 2006 22:12:17 -0000 Received: (qmail 6350 invoked by uid 22791); 14 Mar 2006 22:12:16 -0000 X-Spam-Status: No, hits=-2.5 required=5.0 tests=AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from fmr21.intel.com (HELO scsfmr001.sc.intel.com) (143.183.121.13) by sourceware.org (qpsmtpd/0.31) with ESMTP; Tue, 14 Mar 2006 22:12:14 +0000 Received: from scsfmr100.sc.intel.com (scsfmr100.sc.intel.com [10.3.253.9]) by scsfmr001.sc.intel.com (8.12.10/8.12.10/d: major-outer.mc,v 1.1 2004/09/17 17:50:56 root Exp $) with ESMTP id k2EMC8Dw031960; Tue, 14 Mar 2006 22:12:08 GMT Received: from unix-os.sc.intel.com (unix-os.sc.intel.com [172.25.110.7]) by scsfmr100.sc.intel.com (8.12.10/8.12.10/d: major-inner.mc,v 1.2 2004/09/17 18:05:01 root Exp $) with ESMTP id k2EMCEE4012880; Tue, 14 Mar 2006 22:12:14 GMT Received: (from askeshav@localhost) by unix-os.sc.intel.com (8.11.6/8.11.2) id k2EMC8Q07622; Tue, 14 Mar 2006 14:12:08 -0800 Date: Tue, 14 Mar 2006 22:12:00 -0000 From: Keshavamurthy Anil S To: Ananth N Mavinakayanahalli Cc: SystemTAP Subject: Re: [RFC/PATCH] replace preempt_* calls with rcu_read_* variants Message-ID: <20060314141207.A7579@unix-os.sc.intel.com> Reply-To: Keshavamurthy Anil S References: <20060314134415.GA16136@in.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <20060314134415.GA16136@in.ibm.com>; from ananth@in.ibm.com on Tue, Mar 14, 2006 at 05:44:15AM -0800 X-Scanned-By: MIMEDefang 2.52 on 10.3.253.9 X-IsSubscribed: yes Mailing-List: contact systemtap-help@sourceware.org; run by ezmlm Precedence: bulk List-Subscribe: List-Post: List-Help: , Sender: systemtap-owner@sourceware.org X-SW-Source: 2006-q1/txt/msg00784.txt.bz2 On Tue, Mar 14, 2006 at 05:44:15AM -0800, Ananth N Mavinakayanahalli wrote: > > Hi, > > Can somebody please remind me why we are not using > rcu_read_unlock/lock() > to RCU protect the kprobe handlers, instead, are using > preempt_disable/enable()? "In some realtime-friendly RCU implementations, the RCU read-side critical sections do not disable preemption. So, if you are using synchronize_sched() on the update side, you need to use preempt_disable() (or some other primitive that disables preemption, for example, any of the primitives that disables hardware interrupts) on the read side." http://www.ussg.iu.edu/hypermail/linux/kernel/0510.2/0537.html -thanks, -Anil