Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v2] cpu/hotplug: Set st->cpu earlier | Date | Tue, 22 Mar 2022 23:58:09 +0100 |
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On Tue, Mar 22 2022 at 15:59, Vincent Donnefort wrote: > On 22/03/2022 15:31, Thomas Gleixner wrote: >> On Wed, Mar 16 2022 at 15:36, Steven Price wrote: >>> Setting the 'cpu' member of struct cpuhp_cpu_state in cpuhp_create() is >>> too late as other callbacks can be made before that point. >> >> What? >> >> CPUHP_OFFLINE = 0, >> CPUHP_CREATE_THREADS, >> >> The create threads callback is the very first callback which is invoked >> for a to be plugged CPU on the control CPU. So which earlier callback >> can be invoked and fail? >> >> Thanks, >> >> tglx > > > CPUHP_CREATE_THREADS itself can fail, before st->cpu is set.
Sure. But that does not explain the problem.
> Also, that value is used outside of the callbacks (cpuhp_set_state() > in _cpu_up()).
And why on earth is this not spelled out in the changelog?
> But indeed this description could be refined a bit.
Indeed. But the description is not the only problem here:
It's completely uncomprehensible from the code in _cpu_up() _WHY_ this
st->cpu = cpu;
assignment has to be there.
It's non-sensical if you really think about it, right?
That said, I'm pretty sure you can come up with:
- a proper one time initialization of @st which solves your problem
- a proper changelog which explains it
Thanks,
tglx
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