Re: [PATCH] LoongArch: Implement stable timer shutdown interface

[maobibo]

Xuerui,

Thanks for reviewing my patch, and I reply inline.

On 2023/11/16 下午3:09, WANG Xuerui wrote:
> Hi,
>
> Sorry for the late review but here we go:
>
> On 11/14/23 19:46, Bibo Mao wrote:
> > When cpu is hotplug out, cpu is in idle state and function
> "When a CPU is hot-unplugged, it is put into idle state and the function 
> ... is called"
Will do in next patch.

> > arch_cpu_idle_dead is called. Timer interrupt for this processor should
> > be disabled, else there will be timer interrupt for the dead cpu. Also
> > this prevents vcpu to schedule out during halt-polling flow when system
> > is running in vm mode, since there is pending timer interrupt.
>
> The logical relationship is a bit unclear, is my paraphrasing correct in 
> your opinion?
>
> "Timer interrupt for this processor should be disabled, else a pending 
> timer interrupt will prevent the vCPU from scheduling out during the 
> halt-polling flow when system is running in VM mode"
>
> (I don't immediately know what a "schedule out" is. Is that a 
> translation artifact or some KVM jargon?)
how about "prevent the vCPU from giving up scheduling"?

> > This patch adds detailed implementation for timer shutdown interface, so
> > that timer will be disabled when cpu is plug-out.
>
> Missing some definite articles too.
>
> "This patch implements the timer shutdown interface so that the timer 
> will be properly disabled when a CPU is hot-unplugged"
>
> Is this version better?
sure, will do in next version.

Regards
Bibo Mao
> > Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
> > ---
> >   arch/loongarch/kernel/time.c | 9 ++-------
> >   1 file changed, 2 insertions(+), 7 deletions(-)
> >
> > diff --git a/arch/loongarch/kernel/time.c b/arch/loongarch/kernel/time.c
> > index 3064af94db9c..2920770e30a9 100644
> > --- a/arch/loongarch/kernel/time.c
> > +++ b/arch/loongarch/kernel/time.c
> > @@ -58,7 +58,7 @@ static int constant_set_state_oneshot(struct 
> > clock_event_device *evt)
> >       return 0;
> >   }
> > -static int constant_set_state_oneshot_stopped(struct 
> > clock_event_device *evt)
> > +static int constant_set_state_shutdown(struct clock_event_device *evt)
> >   {
> >       unsigned long timer_config;
> > @@ -90,11 +90,6 @@ static int constant_set_state_periodic(struct 
> > clock_event_device *evt)
> >       return 0;
> >   }
> > -static int constant_set_state_shutdown(struct clock_event_device *evt)
> > -{
> > -    return 0;
> > -}
> > -
> >   static int constant_timer_next_event(unsigned long delta, struct 
> > clock_event_device *evt)
> >   {
> >       unsigned long timer_config;
> > @@ -161,7 +156,7 @@ int constant_clockevent_init(void)
> >       cd->rating = 320;
> >       cd->cpumask = cpumask_of(cpu);
> >       cd->set_state_oneshot = constant_set_state_oneshot;
> > -    cd->set_state_oneshot_stopped = constant_set_state_oneshot_stopped;
> > +    cd->set_state_oneshot_stopped = constant_set_state_shutdown;
> >       cd->set_state_periodic = constant_set_state_periodic;
> >       cd->set_state_shutdown = constant_set_state_shutdown;
> >       cd->set_next_event = constant_timer_next_event;
> >
> > base-commit: 9bacdd8996c77c42ca004440be610692275ff9d0
>
> Otherwise LGTM (regarding the renaming of 
> constant_set_state_oneshot_stopped, both it and the removed 
> constant_set_state_shutdown only has one usage respectively, and looking 
> at the function body it's arguably more appropriate to let it take the 
> "shutdown" name: it's just clearing the enable bit from the CSR.TCFG and 
> nothing else).
>
> With the nits addressed:
>
> Reviewed-by: WANG Xuerui <git@xxxxxxxxxx>