Re: [PATCH V2] clockevents: Fix cpu down race for hrtimer based broadcasting

[Ingo Molnar]

* Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:

> On Thu, Apr 02, 2015 at 12:42:27PM +0200, Ingo Molnar wrote:
> > So why not use a suitable CPU_DOWN* notifier for this, instead of open 
> > coding it all into a random place in the hotplug machinery?
> 
> Because notifiers are crap? ;-) [...]

No doubt - but I didn't feel this poorly named random call into the 
hotplug code, with no comments was any better.

> [...] Its entirely impossible to figure out what's happening to core 
> code in hotplug. You need to go chase down and random order notifier 
> things.
> 
> I'm planning on taking out many of the core hotplug notifiers and 
> hard coding their callbacks into the hotplug code.

That's very welcome news - but please also lets put in place a proper 
namespace for all these callbacks, to make them easy to find and 
change: hotplug_cpu__*() or so, which in this case would turn into 
hotplug_cpu__tick_pull() or so?

> That way at least its clear wtf happens when.

Okay. I'll resurrect the fix with a hotplug_cpu__tick_pull() name - 
agreed?

> > Also, I improved the changelog (attached below), but decided 
> > against applying it until these questions are cleared - please use 
> > that for future versions of this patch.
> 
> 
> > Fixes: http://linuxppc.10917.n7.nabble.com/offlining-cpus-breakage-td88619.html
> 
> You forgot to fix the Fixes line ;-)
> 
> My copy has:
> 
>  Fixes: 5d1638acb9f6 ("tick: Introduce hrtimer based broadcast")

Hm, not sure how that got lost - my git-log of the patch ported on top 
of timers/core still has it:

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