Re: [PATCH v2 4/5] riscv: add lazy preempt support

Guo Ren
2022-09-06T01:46:37Z

On Mon, Sep 5, 2022 at 4:46 PM Sebastian Andrzej Siewior
<bigeasy@linutronix.de> wrote:
>
> On 2022-09-05 16:33:54 [+0800], Guo Ren wrote:
> > > 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?
>
> correct.
Maybe TIF_XXX_RESCHED also could be merged into GENERIC_ENTRY, just
like what you've done in syscall.

struct thread_info {
unsigned long flags;
unsigned long syscall_work; /* SYSCALL_WORK_ flags */
+ unsigned long resched_work; /* RESCHED flags */

Or merge them into one:
struct thread_info {
unsigned long flags;
- unsigned long syscall_work; /* SYSCALL_WORK_ flags */
+ unsigned long ge_flags; /* GENERIC_ENTRY flags */

>
> Sebastian

--
Best Regards
Guo Ren