From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8982EC83000 for ; Wed, 29 Apr 2020 14:07:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6342E208FE for ; Wed, 29 Apr 2020 14:07:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727887AbgD2OHe (ORCPT ); Wed, 29 Apr 2020 10:07:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:39846 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726950AbgD2OHe (ORCPT ); Wed, 29 Apr 2020 10:07:34 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 907E22082E; Wed, 29 Apr 2020 14:07:32 +0000 (UTC) Date: Wed, 29 Apr 2020 10:07:31 -0400 From: Steven Rostedt To: Joerg Roedel Cc: LKML , Ingo Molnar , Thomas Gleixner , Peter Zijlstra , Borislav Petkov , Andrew Morton , Shile Zhang , Andy Lutomirski , "Rafael J. Wysocki" , Dave Hansen , Tzvetomir Stoyanov , Mathieu Desnoyers Subject: Re: [RFC][PATCH] x86/mm: Sync all vmalloc mappings before text_poke() Message-ID: <20200429100731.201312a9@gandalf.local.home> In-Reply-To: <20200429082854.6e1796b5@oasis.local.home> References: <20200429054857.66e8e333@oasis.local.home> <20200429105941.GQ30814@suse.de> <20200429082854.6e1796b5@oasis.local.home> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; 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 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 29 Apr 2020 08:28:54 -0400 Steven Rostedt wrote: > On Wed, 29 Apr 2020 12:59:41 +0200 > Joerg Roedel wrote: > > > > use_temporary_mm() { > > > switch_mm_irqs_off() { > > > load_new_mm_cr3() { > > > write_cr3() <<--- Lock up! > > > > I don't see how it could lock up in write_cr3(), at least on bare-metal. > > What is the environment this happens, 32 or 64 bit, in a VM or > > bare-metal? > > 64 bit bare-metal. In fact, it wasn't reproducible on a VM (according > to Tzvetomir, who was just using a Fedora kernel). I only tried it on > bare-metal. > > > > > I think it is more likely that your lockup is actually a page-fault > > loop, where the #PF handler does not map the faulting address correctly. > > Sounds reasonable. > > > > > But I have to look closer into how text_poke() works before I can say > > more. > > > > Btw, in case it happens on x86-64, does it also happen without > > vmalloc-stacks? > > Just tried it out with !CONFIG_VMAP_STACKS and it still locks up :-/ Talking with Mathieu about this on IRC, he pointed out that my code does have a vzalloc() that is called: in trace_pid_write() pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3); This is done when -P1,2 is on the trace-cmd command line. -- Steve