From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755404AbeASCh3 (ORCPT ); Thu, 18 Jan 2018 21:37:29 -0500 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:36074 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752855AbeASChT (ORCPT ); Thu, 18 Jan 2018 21:37:19 -0500 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.222.184 X-Original-MAILFROM: byungchul.park@lge.com Subject: Re: [PATCH v5 1/2] printk: Add console owner and waiter logic to load balance console writes To: Steven Rostedt Cc: Petr Mladek , Sergey Senozhatsky , akpm@linux-foundation.org, linux-mm@kvack.org, Cong Wang , Dave Hansen , Johannes Weiner , Mel Gorman , Michal Hocko , Vlastimil Babka , Peter Zijlstra , Linus Torvalds , Jan Kara , Mathieu Desnoyers , Tetsuo Handa , rostedt@rostedt.homelinux.com, Sergey Senozhatsky , Tejun Heo , Pavel Machek , linux-kernel@vger.kernel.org, kernel-team@lge.com References: <20180110132418.7080-1-pmladek@suse.com> <20180110132418.7080-2-pmladek@suse.com> <20180117120446.44ewafav7epaibde@pathway.suse.cz> <4a24ce1d-a606-3add-ec30-91ce9a1a1281@lge.com> <20180117211953.2403d189@vmware.local.home> <171cf5b9-2cb6-8e70-87f5-44ace35c2ce4@lge.com> <20180118102139.43c04de5@gandalf.local.home> From: Byungchul Park Message-ID: <45bc7a00-2f7f-3319-bfed-e7b9cd7a8571@lge.com> Date: Fri, 19 Jan 2018 11:37:13 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <20180118102139.43c04de5@gandalf.local.home> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 1/19/2018 12:21 AM, Steven Rostedt wrote: > On Thu, 18 Jan 2018 13:01:46 +0900 > Byungchul Park wrote: > >>> I disagree. It is like a spinlock. You can say a spinlock() that is >>> blocked is also waiting for an event. That event being the owner does a >>> spin_unlock(). >> >> That's exactly what I was saying. Excuse me but, I don't understand >> what you want to say. Could you explain more? What do you disagree? > > I guess I'm confused at what you are asking for then. Sorry for not enough explanation. What I asked you for is: 1. Relocate acquire()s/release()s. 2. So make it simpler and remove unnecessary one. 3. So make it look like the following form, because it's a thing simulating "wait and event". A context --------- lock_map_acquire(wait); /* Or lock_map_acquire_read(wait) */ /* "Read" one is better though.. */ /* A section, we suspect a wait for an event might happen. */ ... lock_map_release(wait); The place actually doing the wait --------------------------------- lock_map_acquire(wait); lock_map_release(wait); wait_for_event(wait); /* Actually do the wait */ Honestly, you used acquire()s/release()s as if they are cross- release stuff which mainly handles general waits and events, not only things doing "acquire -> critical area -> release". But that's not in the mainline at the moment. >>> I find your way confusing. I'm simulating a spinlock not a wait for >>> completion. A wait for completion usually initiates something then >> >> I used the word, *event* instead of *completion*. wait_for_completion() >> and complete() are just an example of a pair of waiter and event. >> Lock and unlock can also be another example, too. >> >> Important thing is that who waits and who triggers the event. Using the >> pair, we can achieve various things, for examples: >> >> 1. Synchronization like wait_for_completion() does. >> 2. Control exclusively entering into a critical area. >> 3. Whatever. >> >>> waits for it to complete. This is trying to get into a critical area >>> but another task is currently in it. It's simulating a spinlock as far >>> as I can see. >> >> Anyway it's an example of "waiter for an event, and the event". >> >> JFYI, spinning or sleeping does not matter. Those are just methods to ^ whether spining or sleeping doesn't matter. >> achieve a wait. I know you're not talking about this though. It's JFYI. > > OK, if it is just FYI. Actually, the last paragraph is JFYI tho. > -- Steve > > > -- Thanks, Byungchul