On Mon, Sep 5, 2022 at 2:34 PM Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote: > > On 2022-09-04 23:16:12 [+0800], Guo Ren wrote: > > > diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S > > > index b9eda3fcbd6d..595100a4c2c7 100644 > > > --- a/arch/riscv/kernel/entry.S > > > +++ b/arch/riscv/kernel/entry.S > > > @@ -361,9 +361,14 @@ restore_all: > > > resume_kernel: > > > REG_L s0, TASK_TI_PREEMPT_COUNT(tp) > > > bnez s0, restore_all > > > - REG_L s0, TASK_TI_FLAGS(tp) > > > - andi s0, s0, _TIF_NEED_RESCHED > > > + REG_L s1, TASK_TI_FLAGS(tp) > > > + andi s0, s1, _TIF_NEED_RESCHED > > > + bnez s0, 1f > > > + REG_L s0, TASK_TI_PREEMPT_LAZY_COUNT(tp) > > > + bnez s0, restore_all > > > + andi s0, s1, _TIF_NEED_RESCHED_LAZY > > Can you tell me, who increased/decreased the PREEMPT_LAZY_COUNT? And > > who set NEED_RESCHED_LAZY? > > There is "generic" code in the PREEMPT_RT patch doing that. The counter > is incremented/ decremented via preempt_lazy_enable()/disable() and one > of the user is migrate_disable()/enable(). > Basically if a task is task_is_realtime() then NEED_RESCHED is set for > the wakeup. For the remaining states (SCHED_OTHER, …) NEED_RESCHED_LAZY > is set for the wakeup. This can be delayed if the task is in a "preempt > disable lazy" section (similar to a preempt_disable() section) but a > task_is_realtime() can still be scheduled if needed. Okay, It should be [PATCH RT]. RISC-V would also move to GENERIC_ENTRY [1], so above assembly code would be replaced by generic one, right? [1]: https://lore.kernel.org/linux-riscv/20220904072637.8619-3-guoren@xxxxxxxxxx/T/#u > See details at > https://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git/plain/patches/sched__Add_support_for_lazy_preemption.patch?h=linux-6.0.y-rt-patches > > Sebastian -- Best Regards Guo Ren
