From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753829Ab3LRMZw (ORCPT ); Wed, 18 Dec 2013 07:25:52 -0500 Received: from mail-qe0-f54.google.com ([209.85.128.54]:47069 "EHLO mail-qe0-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752786Ab3LRMZv (ORCPT ); Wed, 18 Dec 2013 07:25:51 -0500 Date: Wed, 18 Dec 2013 07:25:45 -0500 From: Tejun Heo To: Vaughan Cao Cc: linux-kernel@vger.kernel.org Subject: Re: [PATCH] async: fix insert entry in ascending list Message-ID: <20131218122545.GD4324@htj.dyndns.org> References: <1387336523-13756-1-git-send-email-vaughan.cao@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1387336523-13756-1-git-send-email-vaughan.cao@oracle.com> 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 Hello, On Wed, Dec 18, 2013 at 11:15:23AM +0800, Vaughan Cao wrote: > I suppose there is a fault in the patch of https://lkml.org/lkml/2013/1/16/546. > I know you made a new patch for latest kernel which don't move the entry > between pending and running list that remove the code I mentioned, but our > kernel is based on v3.8.13 that has the code. > > In my understanding, both pending and running list are sorted ascendingly by > cookie value. To find the correct postion to insert the entry into running > list, we traverse reversely to the head. When a node with a smaller cookie is > found, we break out and add the new entry after it. But the origin code tries > to find a larger cookie and insert itself before that node, it won't result in > a sorted list in any direction... Yeah, I should have used list_for_each_entry() there. LOL, I'm an idiot. > I don't know if my understanding about the async mechanism is right, so here > to have a check with you. Thanks. > > Signed-off-by: Vaughan Cao > --- > kernel/async.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/async.c b/kernel/async.c > index 6f34904..596c5e7 100644 > --- a/kernel/async.c > +++ b/kernel/async.c > @@ -135,9 +135,9 @@ static void async_run_entry_fn(struct work_struct *work) > /* 1) move self to the running queue, make sure it stays sorted */ > spin_lock_irqsave(&async_lock, flags); > list_for_each_entry_reverse(pos, &running->domain, list) > - if (entry->cookie < pos->cookie) > + if (entry->cookie > pos->cookie) > break; > - list_move_tail(&entry->list, &pos->list); > + list_move(&entry->list, &pos->list); Hmmm... sadly, upstream doesn't have the ability to backport this. The relevant code path is gone and -stable doesn't backport patches which aren't mainline first. The only way would be backporting through distros, I guess. But, again, this problem shouldn't be noticeable with modern userland and it has been broekn without anyone noticing for long enough, so maybe we can just leave it alone? Thanks. -- tejun