Le Tue, Nov 19, 2024 at 04:34:58PM +0100, Valentin Schneider a écrit :
> +bool ct_set_cpu_work(unsigned int cpu, unsigned int work)
> +{
> + struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
> + unsigned int old;
> + bool ret = false;
> +
> + preempt_disable();
> +
> + old = atomic_read(&ct->state);
> + /*
> + * Try setting the work until either
> + * - the target CPU has entered kernelspace
> + * - the work has been set
> + */
> + do {
> + ret = atomic_try_cmpxchg(&ct->state, &old, old | (work << CT_WORK_START));
> + } while (!ret && ((old & CT_STATE_MASK) != CT_STATE_KERNEL));
> +
> + preempt_enable();
> + return ret;
Does it ignore the IPI even if:
(ret && (old & CT_STATE_MASK) == CT_STATE_KERNEL))
?
And what about CT_STATE_IDLE?
Is the work ignored in those two cases?
But would it be cleaner to never set the work if the target is elsewhere
than CT_STATE_USER. So you don't need to clear the work on kernel exit
but rather on kernel entry.
That is:
bool ct_set_cpu_work(unsigned int cpu, unsigned int work)
{
struct context_tracking *ct = per_cpu_ptr(&context_tracking, cpu);
unsigned int old;
bool ret = false;
preempt_disable();
old = atomic_read(&ct->state);
/* Start with our best wishes */
old &= ~CT_STATE_MASK;
old |= CT_STATE_USER
/*
* Try setting the work until either
* - the target CPU has exited userspace
* - the work has been set
*/
do {
ret = atomic_try_cmpxchg(&ct->state, &old, old | (work << CT_WORK_START));
} while (!ret && ((old & CT_STATE_MASK) == CT_STATE_USER));
preempt_enable();
return ret;
}
Thanks.
