From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757351AbaH1FrN (ORCPT ); Thu, 28 Aug 2014 01:47:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59863 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757129AbaH1FrM (ORCPT ); Thu, 28 Aug 2014 01:47:12 -0400 Date: Thu, 28 Aug 2014 11:16:49 +0530 From: Amit Shah To: Pranith Kumar Cc: "Paul E. McKenney" , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , "open list:READ-COPY UPDATE..." Subject: Re: [PATCH] rcu: Make nocb leader kthreads process pending callbacks after spawning Message-ID: <20140828054649.GJ13052@grmbl.mre> References: <1409172220-2804-1-git-send-email-bobby.prani@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1409172220-2804-1-git-send-email-bobby.prani@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On (Wed) 27 Aug 2014 [16:43:40], Pranith Kumar wrote: > The nocb callbacks generated before the nocb kthreads are spawned are > enqueued in the nocb queue for later processing. Commit fbce7497ee5af ("rcu: > Parallelize and economize NOCB kthread wakeups") introduced nocb leader kthreads > which checked the nocb_leader_wake flag to see if there were any such pending > callbacks. A case was reported in which newly spawned leader kthreads were not > processing the pending callbacks as this flag was not set, which led to a boot > hang. > > The following commit ensures that the newly spawned nocb kthreads process the > pending callbacks by allowing the kthreads to run immediately after spawning > instead of waiting. This is done by inverting the logic of nocb_leader_wake > tests to nocb_leader_sleep which allows us to use the default initialization of > this flag to 0 to let the kthreads run. > > Reported-by: Amit Shah > Signed-off-by: Pranith Kumar > Link: http://www.spinics.net/lists/kernel/msg1802899.html > --- > kernel/rcu/tree.h | 2 +- > kernel/rcu/tree_plugin.h | 24 ++++++++++++------------ > 2 files changed, 13 insertions(+), 13 deletions(-) I'd have split this into two patches: one for the variable rename and one for fixing the bug. However, the backport Paul posted does work fine for me on master, so you can add my Tested-by: Amit Shah Thanks, Amit