Le Wed, Nov 20, 2024 at 11:54:36AM +0100, Frederic Weisbecker a écrit :
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; }
Ah but there is CT_STATE_GUEST and I see the last patch also applies that to CT_STATE_IDLE.
So that could be:
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);
/* CT_STATE_IDLE can be added to last patch here */ if (!(old & (CT_STATE_USER | CT_STATE_GUEST))) { old &= ~CT_STATE_MASK; old |= CT_STATE_USER; }
/* * Try setting the work until either * - the target CPU has exited userspace / guest * - the work has been set */ do { ret = atomic_try_cmpxchg(&ct->state, &old, old | (work << CT_WORK_START)); } while (!ret && old & (CT_STATE_USER | CT_STATE_GUEST));
preempt_enable();
return ret; }
Thanks.