Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752342AbaFLUZh (ORCPT ); Thu, 12 Jun 2014 16:25:37 -0400 Received: from mail-pb0-f49.google.com ([209.85.160.49]:43646 "EHLO mail-pb0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751811AbaFLUZf (ORCPT ); Thu, 12 Jun 2014 16:25:35 -0400 Date: Thu, 12 Jun 2014 13:26:02 -0700 From: Kent Overstreet To: Benjamin LaHaise Cc: Mike Galbraith , Lai Jiangshan , RT , LKML , Sebastian Andrzej Siewior , Steven Rostedt , Thomas Gleixner , "Paul E. McKenney" Subject: Re: [RFC PATCH V2] rt/aio: fix rcu garbage collection might_sleep() splat Message-ID: <20140612202602.GI10871@kmo-pixel> References: <1402216538.31630.7.camel@marge.simpson.net> <5395172E.4010007@cn.fujitsu.com> <1402372048.5124.20.camel@marge.simpson.net> <20140610175001.GF27015@kvack.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140610175001.GF27015@kvack.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jun 10, 2014 at 01:50:01PM -0400, Benjamin LaHaise wrote: > On Tue, Jun 10, 2014 at 05:47:28AM +0200, Mike Galbraith wrote: > > On Mon, 2014-06-09 at 10:08 +0800, Lai Jiangshan wrote: > > > Hi, rt-people > > > > > > I don't think it is the correct direction. > > > Softirq (including local_bh_disable()) in RT kernel should be preemptible. > > > > How about the below then? > > > > I was sorely tempted to post a tiny variant that dropped taking ctx_lock > > in free_ioctx_users() entirely, as someone diddling with no reference > > didn't make sense. Cc Ben, he would know. > > That should be okay... Let's ask Kent to chime in on whether this looks > safe to him on the percpu ref front as well, since he's the one who wrote > this code. Ok, finally got around to reading the whole thread - honestly, I would just punt to workqueue to do the free_ioctx_users(). AFAICT that should be perfectly safe and even aside from rt it would be good change so we're not cancelling an arbitrary number of kiocbs from rcu callback context. Kind of a related change, it should be possible to just grab the entire list of kiocbs with ctx_lock held (remove them all at once from ctx->active_reqs), then cancel them without ctx_lock held. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/