From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938668AbdAESvA (ORCPT ); Thu, 5 Jan 2017 13:51:00 -0500 Received: from smtprelay0068.hostedemail.com ([216.40.44.68]:56558 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1759766AbdAESuY (ORCPT ); Thu, 5 Jan 2017 13:50:24 -0500 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::::::::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1437:1515:1516:1518:1534:1540:1593:1594:1711:1730:1747:1777:1792:2393:2553:2559:2562:3138:3139:3140:3141:3142:3352:3622:3865:3866:3867:3868:3870:3871:3872:3873:3874:5007:6119:6120:6261:7875:7974:10004:10400:10848:10967:11026:11232:11658:11914:12295:12296:12740:12760:12895:13069:13311:13357:13439:14096:14097:14181:14659:14721:21080:21325:30054:30090:30091,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0,LFtime:3,LUA_SUMMARY:none X-HE-Tag: party76_203cd6dc6b708 X-Filterd-Recvd-Size: 2118 Date: Thu, 5 Jan 2017 13:50:20 -0500 From: Steven Rostedt To: Waiman Long Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , linux-kernel@vger.kernel.org, Daniel Bristot de Oliveira Subject: Re: [RFC PATCH 0/7] locking/rtqspinlock: Realtime queued spinlocks Message-ID: <20170105135020.40187dfa@gandalf.local.home> In-Reply-To: <82624801-740f-9088-f6fb-7812f10fa146@redhat.com> References: <1483466430-8028-1-git-send-email-longman@redhat.com> <20170104124929.GI25813@worktop.programming.kicks-ass.net> <57c0a6e1-1fab-b8d4-2a68-02cc1ebf7ce6@redhat.com> <20170105094439.GD3093@worktop> <342e0af6-43b1-76ea-0f0b-55087dfec96c@redhat.com> <20170105160834.GB3107@twins.programming.kicks-ass.net> <82624801-740f-9088-f6fb-7812f10fa146@redhat.com> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 5 Jan 2017 12:07:21 -0500 Waiman Long wrote: > I do make the assumption that spinlock critical sections are behaving > well enough. Apparently, that is not a valid assumption. I sent these > RFC patches out to see if it was an idea worth pursuing. If not, I can > drop these patches. Anyway, thanks for the feedback. Yes, the assumption is incorrect. There are places that can hold a spin lock for several hundreds of microseconds. If you can't preempt them, you'll never get below several hundreds of microseconds in latency. And it would be hard to pick and choose (we already do this to decide what can be a raw_spin_lock), because you need to audit all use cases of a spin_lock as well as all the locks taken while holding that spin_lock. -- Steve