[PATCH] ARM: smp: Remove CPU: shutdown notice

Russell King - ARM Linux linux at armlinux.org.uk
Tue Jan 17 15:23:14 PST 2017

On Tue, Jan 17, 2017 at 03:07:12PM -0800, Florian Fainelli wrote:
> This message is not particularly informative, and is not paired with an
> identical message when a CPU is brought online. Finally, it slows the
> CPU hotplug path down, thus allowing less CPU hotplug operations per
> second. Just remove it.

CPU hotplug isn't a fast operation anyway - it's also fairly disruptive
in that it uses stop_machine() to halt activity everywhere while taking
the CPU offline.

If you're worried about a single printk slowing things down, it sounds
like you're doing something wrong here - maybe you should be using
cpuidle for power management rather than trying to make CPU hotplug do
that for you?

A rapidly changing CPU hotplug state has other side effects - such as
reading /proc/interrupts is meaningless, because as soon as you've read
it the CPUs could have changed.  It also makes a farce of spreading
interrupts over the available CPUs.

All in all, I don't think this is a good idea...

RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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