From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754498AbaEMTdl (ORCPT ); Tue, 13 May 2014 15:33:41 -0400 Received: from mail-wi0-f178.google.com ([209.85.212.178]:34786 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751511AbaEMTdf (ORCPT ); Tue, 13 May 2014 15:33:35 -0400 Date: Tue, 13 May 2014 21:33:29 +0200 From: Frederic Weisbecker To: Peter Zijlstra Cc: LKML , Andrew Morton , Ingo Molnar , Kevin Hilman , "Paul E. McKenney" , Thomas Gleixner , Viresh Kumar Subject: Re: [PATCH 1/5] irq_work: Let arch tell us if it can raise irq work Message-ID: <20140513193327.GF13828@localhost.localdomain> References: <1399991921-17618-1-git-send-email-fweisbec@gmail.com> <1399991921-17618-2-git-send-email-fweisbec@gmail.com> <20140513170942.GC5226@laptop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140513170942.GC5226@laptop.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 13, 2014 at 07:09:42PM +0200, Peter Zijlstra wrote: > On Tue, May 13, 2014 at 04:38:37PM +0200, Frederic Weisbecker wrote: > > We prepare for executing the full nohz kick through an irq work. But > > if we do this as is, we'll run into conflicting tick locking: the tick > > holds the hrtimer lock and the nohz kick may do so too. > > It does? How does the tick end up holding that lock? > > Normal hrtimer callbacks run without holding the hrtimer lock -- I made > it so. > > This means tick_sched_timer() is called without hrtimer lock, and I > don't see it taking it anywhere in tick_sched_do_timer() or > tick_sched_handle(). Check hrtimer_interrupt(), it takes the per cpu base->lock.