Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756668AbcK2JRD (ORCPT ); Tue, 29 Nov 2016 04:17:03 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:35594 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756370AbcK2JQz (ORCPT ); Tue, 29 Nov 2016 04:16:55 -0500 Date: Tue, 29 Nov 2016 10:16:50 +0100 From: Peter Zijlstra To: Josh Poimboeuf Cc: "Paul E. McKenney" , Vince Weaver , "linux-kernel@vger.kernel.org" , Ingo Molnar , Arnaldo Carvalho de Melo , "dvyukov@google.com" Subject: Re: perf: fuzzer BUG: KASAN: stack-out-of-bounds in __unwind_start Message-ID: <20161129091650.GA3092@twins.programming.kicks-ass.net> References: <20161128215411.fkis7bbimjy4v4j7@treble> <20161129004021.GL3924@linux.vnet.ibm.com> <20161129055241.6dy2dt4q4ptazk2s@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161129055241.6dy2dt4q4ptazk2s@treble> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 749 Lines: 17 On Mon, Nov 28, 2016 at 11:52:41PM -0600, Josh Poimboeuf wrote: > > We used to do that, but the resulting NMIs were problematic on some > > platforms. Perhaps things have gotten better? > > Did a little digging on git blame and found the following commit (which > seems to be the cause of the KASAN warning and missing stack dump): > > bc1dce514e9b ("rcu: Don't use NMIs to dump other CPUs' stacks") > > I presume this commit is still needed because of the NMI printk deadlock > issues which were discussed at Kernel Summit. I guess those issues need > to be sorted out before the above commit can be reverted. so printk should more or less work from NMI, esp. after: 42a0bb3f7138 ("printk/nmi: generic solution for safe printk in NMI")