Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758014AbYHSVI2 (ORCPT ); Tue, 19 Aug 2008 17:08:28 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752684AbYHSVIS (ORCPT ); Tue, 19 Aug 2008 17:08:18 -0400 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.124]:41515 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751103AbYHSVIR (ORCPT ); Tue, 19 Aug 2008 17:08:17 -0400 Date: Tue, 19 Aug 2008 17:08:15 -0400 (EDT) From: Steven Rostedt X-X-Sender: rostedt@gandalf.stny.rr.com To: Mathieu Desnoyers cc: Benjamin Herrenschmidt , Scott Wood , Eran Liberty , linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org, Steven Rostedt , "Paul E. McKenney" Subject: Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3) In-Reply-To: <20080819173453.GA28239@Krystal> Message-ID: References: <48A9901B.1080900@redhat.com> <20080818154746.GA26835@Krystal> <48A9AFA7.8080508@freescale.com> <1219110814.8062.2.camel@pasglop> <1219113549.8062.13.camel@pasglop> <20080819024707.GA22659@Krystal> <20080819173453.GA28239@Krystal> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1688 Lines: 43 On Tue, 19 Aug 2008, Mathieu Desnoyers wrote: > > Ok, there are two cases where it's ok : > > 1 - in stop_machine, considering we are not touching code executed in > NMI handlers. > 2 - when using my replace_instruction_safe() which uses a temporary > breakpoint when doing the instruction replacement. > > In those cases you could use text_poke_early(). > > See > http://git.kernel.org/?p=linux/kernel/git/compudj/linux-2.6-lttng.git;a=blob;f=arch/x86/kernel/immediate.c;h=7789e2c75bf03e645f15759d5dff0c1698493f92;hb=HEAD > > For a use example. Basically it looks like : > > > 360 pages[0] = virt_to_page((void *)bypass_eip); > 361 vaddr = vmap(pages, 1, VM_MAP, PAGE_KERNEL); > 362 BUG_ON(!vaddr); > 363 text_poke_early(&vaddr[bypass_eip & ~PAGE_MASK], > 364 (void *)addr, size); > 365 /* > 366 * Fill the rest with nops. > 367 */ > 368 len = NR_NOPS - size; > 369 add_nops((void *) > 370 &vaddr[(bypass_eip & ~PAGE_MASK) + size], > 371 len); > 372 print_dbg_bytes("inserted nops", > 373 &vaddr[(bypass_eip & ~PAGE_MASK) + size], len); > 374 vunmap(vaddr); vunmap can not be called with interrupts disabled, and this is exactly what my code does. -- Steve -- 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/