From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755398Ab1GALgi (ORCPT ); Fri, 1 Jul 2011 07:36:38 -0400 Received: from e28smtp05.in.ibm.com ([122.248.162.5]:50917 "EHLO e28smtp05.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755026Ab1GALgi (ORCPT ); Fri, 1 Jul 2011 07:36:38 -0400 Date: Fri, 1 Jul 2011 17:06:26 +0530 From: Ananth N Mavinakayanahalli To: Masami Hiramatsu Cc: Steven Rostedt , LKML , Peter Zijlstra , Frederic Weisbecker , Thomas Gleixner , Ingo Molnar , yrl.pp-manager.tt@hitachi.com Subject: Re: [BUG] kprobes crashing because of preempt count Message-ID: <20110701113626.GB23752@in.ibm.com> Reply-To: ananth@in.ibm.com References: <1309440213.26417.76.camel@gandalf.stny.rr.com> <4E0D1EE3.6080607@hitachi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4E0D1EE3.6080607@hitachi.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jul 01, 2011 at 10:12:03AM +0900, Masami Hiramatsu wrote: > (2011/06/30 22:23), Steven Rostedt wrote: ... > > Do we really need to have preemption disabled throughout this? Is it > > because we don't want to migrate or call schedule? Not sure what the > > best way to fix this is. Perhaps we add a kprobe_preempt_disable() that > > is checked as well? > > I think the best way to do that is just removing preemption disabling > code, because > - breakpoint exception itself disables interrupt (at least on x86) > - While single stepping, interrupts also be disabled. On 64-bit powerpc, kprobe handlers are run with interrupts enabled (MSR_EE = 1), but most instructions (including loads/stores) are emulated, so for the most part, we don't take the sstep exception. Ananth