From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sebastian Andrzej Siewior Subject: Re: [patch V2 43/67] leds/trigger/cpu: Convert to hotplug state machine Date: Fri, 15 Jul 2016 16:10:26 +0200 Message-ID: <20160715141026.GA16938@linutronix.de> References: <20160713153219.128052238@linutronix.de> <20160713153336.465496902@linutronix.de> <57873CFF.1010803@samsung.com> <20160714074713.GA17287@gmail.com> <5787490F.5000105@samsung.com> <20160714094154.GY30154@twins.programming.kicks-ass.net> <57877640.4020004@samsung.com> <57877DAE.8080401@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <57877DAE.8080401@samsung.com> Sender: linux-kernel-owner@vger.kernel.org To: Jacek Anaszewski Cc: Thomas Gleixner , Peter Zijlstra , Ingo Molnar , Anna-Maria Gleixner , LKML , rt@linutronix.de, Richard Cochran , Linus Torvalds , Linus Walleij , Paul Gortmaker , Richard Purdie , linux-leds@vger.kernel.org, Pawel Moll List-Id: linux-leds@vger.kernel.org * Jacek Anaszewski | 2016-07-14 13:55:26 [+0200]: >On 07/14/2016 01:33 PM, Thomas Gleixner wrote: >>That does not explain WHY this needs to happen in the low level bringup phase >>of the CPU with interrupts disabled and can't be done from the normal ONLINE >>callbacks in thread context. > >It was before my time in kernel, so I can only suppose that it was >the easiest way. Does it introduce some problems? It was introduced by Pawel Moll in fba14ae8e924 ("ledtrig-cpu: Handle CPU hot(un)plugging"). It does not introduce any problems but those bring up / bring down levels are usually used by the core code. This does not look like it needs to be done _that_ early or late during the removal / addition of a CPU to the system. Which means this looks like it could be moved to CPU_ONLINE / CPU_DOWN_PREPARE which in turns means we could use dynamic IDs instead of those hardcoded ones since the LED subsystem does not depend on other components. Sebastian