From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756962AbaDHQKg (ORCPT ); Tue, 8 Apr 2014 12:10:36 -0400 Received: from merlin.infradead.org ([205.233.59.134]:42731 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756317AbaDHQKe (ORCPT ); Tue, 8 Apr 2014 12:10:34 -0400 Date: Tue, 8 Apr 2014 18:10:23 +0200 From: Peter Zijlstra To: Sasha Levin Cc: Ingo Molnar , Andrew Morton , "linux-mm@kvack.org" , LKML , Dave Jones , Thomas Gleixner Subject: Re: sched: long running interrupts breaking spinlocks Message-ID: <20140408161023.GP10526@twins.programming.kicks-ass.net> References: <53441540.7070102@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <53441540.7070102@oracle.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Apr 08, 2014 at 11:26:56AM -0400, Sasha Levin wrote: > Hi all, > > (all the below happened inside mm/ code, so while I don't suspect > it's a mm/ issue you folks got cc'ed anyways!) > > While fuzzing with trinity inside a KVM tools guest running the latest -next > kernel, I've stumbled on the following: > > [ 4071.166362] BUG: spinlock lockup suspected on CPU#19, trinity-c19/17092 That's a heuristic in the spinlock code; triggering it with big machines (19 cpus is far bigger than anything at the time that code was written) and virt (yay for lock owner preemption; another thing we didn't have back when) is trivial. I'd not worry too much about this. So DEBUG_SPINLOCKS turns spin_lock() into something like: for (i = 0; i < loops; i++) if (spin_trylock()) return; /* complain */ And you simply ran out of loops.