/*
* As outlined at the top, provides a fast, high resolution, nanosecond
* time source that is monotonic per cpu argument and has bounded drift
* between cpus.
*
* ######################### BIG FAT WARNING ##########################
* # when comparing cpu_clock(i) to cpu_clock(j) for i != j, time can #
* # go backwards !! #
* ####################################################################
*/
u64 cpu_clock(int cpu)
{
u64 clock;
unsigned long flags;
flags = hard_local_irq_save_notrace();
clock = sched_clock_cpu(cpu);
hard_local_irq_restore_notrace(flags);
return clock;
}
/*
* Similar to cpu_clock() for the current cpu. Time will only be observed
* to be monotonic if care is taken to only compare timestampt taken on the
* same CPU.
*
* See cpu_clock().
*/
u64 local_clock(void)
{
u64 clock;
unsigned long flags;
flags = hard_local_irq_save_notrace();
clock = sched_clock_cpu(smp_processor_id());
hard_local_irq_restore_notrace(flags);
return clock;
}
int notrace __ipipe_check_percpu_access(void)
{
struct ipipe_percpu_domain_data *p;
struct ipipe_domain *this_domain;
unsigned long flags;
int ret = 0;
flags = hard_local_irq_save_notrace();
/*
* Don't use __ipipe_current_domain here, this would recurse
* indefinitely.
*/
this_domain = __this_cpu_read(ipipe_percpu.curr)->domain;
/*
* Only the root domain may implement preemptive CPU migration
* of tasks, so anything above in the pipeline should be fine.
*/
if (this_domain != ipipe_root_domain)
goto out;
if (raw_irqs_disabled_flags(flags))
goto out;
/*
* Last chance: hw interrupts were enabled on entry while
* running over the root domain, but the root stage might be
* currently stalled, in which case preemption would be
* disabled, and no migration could occur.
*/
if (this_domain == ipipe_root_domain) {
p = ipipe_this_cpu_root_context();
if (test_bit(IPIPE_STALL_FLAG, &p->status))
goto out;
}
/*
* Our caller may end up accessing the wrong per-cpu variable
* instance due to CPU migration; tell it to complain about
* this.
*/
ret = 1;
out:
hard_local_irq_restore_notrace(flags);
return ret;
}