Re: [tip:sched/core] [sched/fair] 79104becf4: BUG:kernel_NULL_pointer_dereference,address

[Fernand Sieber <sieberf@amazon.com>]

Hi Peter,

> But yeah, if the task holding your resource is doing yield() you're
> 'sad'. Basically a sched-fair yield() means: I've no fucking clue what
> I'm doing and lets hope we can make progress a little later.
>
> And it gets worse in the context of PI/proxy, because in that case your
> fair task can deadlock the system through sheer incompetence.
>
> Anyway, consider the PI case, we bump a fair task to FIFO and then
> yield() would do the FIFO yield -- with all the possible problems.
>
> And we want the same for proxy, if the boosting context is FIFO, we want
> a FIFO yield.

Alright, makes sense. Based on your suggestion I've submitted a patch:
lore.kernel.org/lkml/20251106104022.195157-1-sieberf@amazon.com/T/#u

This is essentially the same as your suggestion + handling of yield to and
scx.

Also confirmed no crashes with this patch + v3 of the vruntime forfeit patch
https://lore.kernel.org/lkml/20250918150528.292620-1-sieberf@amazon.com/

--Fernand



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