From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f174.google.com (mail-ie0-f174.google.com [209.85.223.174]) by kanga.kvack.org (Postfix) with ESMTP id D27DC6B0037 for ; Tue, 8 Apr 2014 12:10:31 -0400 (EDT) Received: by mail-ie0-f174.google.com with SMTP id rp18so1110820iec.5 for ; Tue, 08 Apr 2014 09:10:31 -0700 (PDT) Received: from merlin.infradead.org (merlin.infradead.org. [2001:4978:20e::2]) by mx.google.com with ESMTPS id ij6si3964643igb.29.2014.04.08.09.10.27 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Apr 2014 09:10:27 -0700 (PDT) Date: Tue, 8 Apr 2014 18:10:23 +0200 From: Peter Zijlstra 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> Sender: owner-linux-mm@kvack.org List-ID: To: Sasha Levin Cc: Ingo Molnar , Andrew Morton , "linux-mm@kvack.org" , LKML , Dave Jones , Thomas Gleixner 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. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org