With the intent to provide local_clock_noinstr(), a variant of
local_clock() that's safe to be called from noinstr code (with the
assumption that any such code will already be non-preemptible),
prepare for things by providing a noinstr sched_clock_read() function.
Specifically, preempt_enable_*() calls out to schedule(), which upsets
noinstr validation efforts.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Michael Kelley <mikelley@microsoft.com> # Hyper-V
Link: https://lore.kernel.org/r/20230519102715.502547082@infradead.org
#ifndef __ASSEMBLY__
-static inline u64 drdtime(void)
+static __always_inline u64 drdtime(void)
{
int rID = 0;
u64 val = 0;
return drdtime();
}
-static u64 native_sched_clock(void)
+static noinstr u64 sched_clock_read(void)
{
- return read_const_counter(NULL);
+ return drdtime();
}
static struct clocksource clocksource_const = {
res = clocksource_register_hz(&clocksource_const, freq);
- sched_clock_register(native_sched_clock, 64, freq);
+ sched_clock_register(sched_clock_read, 64, freq);
pr_info("Constant clock source device register\n");