From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: Linux 3.16-rc6 Date: Thu, 24 Jul 2014 20:36:43 +0200 Message-ID: <20140724183643.GM3935@laptop> References: <20140723095327.GA23131@pd.tnic> <20140724064353.GW9918@twins.programming.kicks-ass.net> <20140724084126.GB19239@pd.tnic> <20140724122513.GM19239@pd.tnic> <20140724125814.GX6758@twins.programming.kicks-ass.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from bombadil.infradead.org ([198.137.202.9]:37480 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751250AbaGXSgz (ORCPT ); Thu, 24 Jul 2014 14:36:55 -0400 Content-Disposition: inline In-Reply-To: Sender: linux-input-owner@vger.kernel.org List-Id: linux-input@vger.kernel.org To: Linus Torvalds Cc: Borislav Petkov , Waiman Long , Ingo Molnar , Linux Kernel Mailing List , USB list , "linux-input@vger.kernel.org" On Thu, Jul 24, 2014 at 11:18:16AM -0700, Linus Torvalds wrote: > On Thu, Jul 24, 2014 at 5:58 AM, Peter Zijlstra wrote: > > > > So going by the nifty picture rostedt made: > > > > [ 61.454336] CPU0 CPU1 > > [ 61.454336] ---- ---- > > [ 61.454336] lock(&(&p->alloc_lock)->rlock); > > [ 61.454336] local_irq_disable(); > > [ 61.454336] lock(tasklist_lock); > > [ 61.454336] lock(&(&p->alloc_lock)->rlock); > > [ 61.454336] > > [ 61.454336] lock(tasklist_lock); > > So this *should* be fine. It always has been in the past, and it was > certainly the *intention* that it should continue to work with > qrwlock, even in the presense of pending writers on other cpu's. > > The qrwlock rules are that a read-lock in an interrupt is still going > to be unfair and succeed if there are other readers. Ah, indeed. Should have checked :/ > So it sounds to me like the new lockdep rules in tip/master are too > strict and are throwing a false positive. Right. Waiman can you have a look?