On 16/11/21 14:41, Christophe Leroy wrote: > Le 10/11/2021 à 21:24, Valentin Schneider a écrit : >> Per PREEMPT_DYNAMIC, checking CONFIG_PREEMPT doesn't tell you the actual >> preemption model of the live kernel. Use the newly-introduced accessors >> instead. > > Is that change worth it for now ? As far as I can see powerpc doesn't > have DYNAMIC PREEMPT, a lot of work needs to be done before being able > to use it: > - Implement GENERIC_ENTRY > - Implement STATIC_CALLS (already done on PPC32, to be done on PPC64) > You're right, I ditched this patch for v3 - AFAICT the change wasn't even valid as the preempt_schedule_irq() call needs to be replaced with irqentry_exit_cond_resched() (IOW this needs to make use of the generic entry code). >> >> sched_init() -> preempt_dynamic_init() happens way before IRQs are set up, >> so this should be fine. > > It looks like you are mixing up interrupts and IRQs (also known as > "external interrupts"). > > ISI (Instruction Storage Interrupt) and DSI (Data Storage Interrupt) for > instance are also interrupts. They happen everytime there is a page > fault so may happen pretty early. > > Traps generated by WARN_ON() are also interrupts that may happen at any > time. > Michael pointed this out and indeed triggering a WARN_ON() there is not super smart. Thanks for teaching me a bit of what I'm putting my grubby hands in :)
