Re: [patch V2 43/67] leds/trigger/cpu: Convert to hotplug state machine

From: Jacek Anaszewski
Date: Mon Jul 18 2016 - 04:26:46 EST

Hi Sebastian,

On 07/15/2016 04:10 PM, Sebastian Andrzej Siewior wrote:
* 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

From the LED subsystem perspective I don't see any particular reason
for which it couldn't be accomplished from the ONLINE callbacks.

Best regards,
Jacek Anaszewski