From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755193AbbAFNDf (ORCPT ); Tue, 6 Jan 2015 08:03:35 -0500 Received: from casper.infradead.org ([85.118.1.10]:54060 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754856AbbAFNDe (ORCPT ); Tue, 6 Jan 2015 08:03:34 -0500 Date: Tue, 6 Jan 2015 14:03:17 +0100 From: Peter Zijlstra To: Kent Overstreet Cc: Sedat Dilek , Dave Jones , Linus Torvalds , LKML , Chris Mason Subject: Re: Linux 3.19-rc3 Message-ID: <20150106130317.GX29390@twins.programming.kicks-ass.net> References: <20150106100621.GL29390@twins.programming.kicks-ass.net> <20150106110112.GQ29390@twins.programming.kicks-ass.net> <20150106110730.GA25846@kmo-pixel> <20150106114215.GS29390@twins.programming.kicks-ass.net> <20150106115645.GA26845@kmo-pixel> <20150106121603.GV29390@twins.programming.kicks-ass.net> <20150106124313.GD26845@kmo-pixel> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150106124313.GD26845@kmo-pixel> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 06, 2015 at 04:43:13AM -0800, Kent Overstreet wrote: > It might make the most sense to cook up something new, stealing some of the > closure code but using standard the wait_queue_head_t - having a single standard > waitlist type is definitely a good thing, and unfortunately I don't think it'd > be a good idea to convert closures to wait_queue_head_t mainly because of the > memory usage. > > I will note that one thing that has been immensely useful with closures is the > ability to pass a closure around - think of it as a "wait object" - to some code > that may end up waiting on something, but you don't want to itself sleep, and > then the caller can closure_sync() or continue_at() or whatever it wants (or use > the same closure for waiting on multiple things, e.g. where we wait on writing > the two new btree nodes after a split). > > Think of it a souped up completion. Yeah I got that aspect. I'm still trying to get my head around how the wait_event bit would be a natural match though ;-) Let me stew a bit on that. That said, the RT people want a simple waitqueue, one that has deterministic behaviour. This is only possibly by removing some of the more obscure waitqueue features and thus also results in a slimmer structure.