From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161172AbWFVQgm (ORCPT ); Thu, 22 Jun 2006 12:36:42 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030645AbWFVQgm (ORCPT ); Thu, 22 Jun 2006 12:36:42 -0400 Received: from e5.ny.us.ibm.com ([32.97.182.145]:50662 "EHLO e5.ny.us.ibm.com") by vger.kernel.org with ESMTP id S1030643AbWFVQgl (ORCPT ); Thu, 22 Jun 2006 12:36:41 -0400 Date: Thu, 22 Jun 2006 09:36:43 -0700 From: Mike Grundy To: Jan Glauber Cc: Martin Schwidefsky , linux-kernel@vger.kernel.org, systemtap@sources.redhat.com Subject: Re: [PATCH] kprobes for s390 architecture Message-ID: <20060622163643.GA3329@localhost.localdomain> Mail-Followup-To: Jan Glauber , Martin Schwidefsky , linux-kernel@vger.kernel.org, systemtap@sources.redhat.com References: <20060612131552.GA6647@localhost.localdomain> <1150141217.5495.72.camel@localhost> <20060621042804.GA20300@localhost.localdomain> <1150907920.8295.10.camel@localhost> <20060621173436.GA7834@localhost.localdomain> <1150975716.6496.9.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1150975716.6496.9.camel@localhost> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 22, 2006 at 01:28:36PM +0200, Jan Glauber wrote: > On Wed, 2006-06-21 at 10:34 -0700, Mike Grundy wrote: > > On Wed, Jun 21, 2006 at 06:38:40PM +0200, Martin Schwidefsky wrote: > > > You misunderstood me here. I'm not talking about storing the same piece > > > of data to memory on each processor. I'm talking about isolating all > > > other cpus so that the initiating cpu can store the breakpoint to memory > > > without running into the danger that another cpu is trying to execute it > > > at the same time. But probably the store should be atomic in regard to > > > instruction fetching on the other cpus. It is only two bytes and it > > > should be aligned. > > Preemption disabling is not necessary around smp_call_function(), since > smp_call_function() takes a spin lock. But smp_call_function() is wrong > here, it calls the code on all other CPUs but not on our own. Please use > on_each_cpu() instead. But on_each_cpu() does: preempt_disable(); ret = smp_call_function(func, info, retry, wait); local_irq_disable(); func(info); local_irq_enable(); preempt_enable(); I'm confused. I really don't need to swap the instruction on each cpu. I really need to make sure each cpu is not fetching that instruction while I change it. s390 doesn't have a flush_icache_range() (which the other arches use after the swap). I thought that the synchronization that smp_call_function() does was the primary reason for using it here, not repeatedly changing the same area of memory. If you'd prefer I use on_each_cpu() instead of smp_call_function(), no problem. Thanks Mike