Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932986AbeAKUnp (ORCPT + 1 other); Thu, 11 Jan 2018 15:43:45 -0500 Received: from mail-it0-f52.google.com ([209.85.214.52]:42369 "EHLO mail-it0-f52.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932377AbeAKUno (ORCPT ); Thu, 11 Jan 2018 15:43:44 -0500 X-Google-Smtp-Source: ACJfBovhyMiCVS4fb2howvhYgeD4glcrz/pSS56SyPJLVqBn1ig6njDTkmAHmXQ/TX0K724dbjVZHQ== From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Thu, 11 Jan 2018 15:43:41 -0500 (EST) X-X-Sender: vince@macbook-air To: Vince Weaver cc: Peter Zijlstra , Josh Poimboeuf , Ingo Molnar , linux-kernel@vger.kernel.org, Ingo Molnar , Arnaldo Carvalho de Melo , Thomas Gleixner , Andy Lutomirski Subject: Re: perf: perf_fuzzer quickly locks up on 4.15-rc7 In-Reply-To: Message-ID: References: <20180109151253.GK6176@hirez.programming.kicks-ass.net> <20180109153341.GL6176@hirez.programming.kicks-ass.net> <20180109160551.GK3040@hirez.programming.kicks-ass.net> <20180109170716.bqmexpmywwr4bwuv@treble> <20180111052538.2qhj6oxnc24xumhk@treble> <20180111192112.d35nkotzklicd27c@treble> <20180111195018.GB3397@worktop> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) 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 Return-Path: On Thu, 11 Jan 2018, Vince Weaver wrote: > On Thu, 11 Jan 2018, Peter Zijlstra wrote: > > > On Thu, Jan 11, 2018 at 01:21:12PM -0600, Josh Poimboeuf wrote: > > > Yuck. This time it was stack recursion on the entry stack. In the > > > previous error, recursion was detected on the IRQ stack. Otherwise they > > > look quite similar. > > > > > > Was that also with nopti? > > > > Both with pti enabled, nopti makes things work again. > > I think I have hit those errors even with pti disabled but now I'll have > to double check. I can confirm this, I am able to trigger the stack recursion warning even when "pti=off" is set. Jan 11 15:34:47 core2 kernel: [ 320.668900] WARNING: stack recursion on stack type 4 Jan 11 15:34:47 core2 kernel: [ 320.668909] WARNING: can't dereference registers at 00000000d5ae0491 for ip swapgs_restore_regs_and_return_to_usermode+0x28/0x7c Vince