[PATCH v5] um: Enable preemption in UML

[Anton Ivanov]

On 22/09/2023 09:41, Johannes Berg wrote:
>> Yes, but when does the fork actually happen?
>>
> Looking further at this, now I'm confused as to why it doesn't happen
> _all_ the time.
>
> I think this has pretty much always been wrong, just now we actually
> notice it?
>
> Basically, when we create a new thread (really just mm I think), we say
> the first thing that has to run there is fork_handler(), which
> initialises things the first time around. This calls force_flush_all()
>
> But of course it's called from __schedule(), which has
> preemption/interrupts disabled. So you can't do mmap_read_lock()?

Stupid question.

If we have preemption and interrupts disabled and we are UP do we really need to lock it at this point?

>
> But I'm confused as to why it doesn't seem happen all the time?
>
> johannes
>
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Anton R. Ivanov
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