clocksource: Move cycle_last validation to core code
The only user of the cycle_last validation is the x86 TSC. In order to
provide NMI safe accessor functions for clock monotonic and
monotonic_raw we need to do that in the core.
We can't do the TSC specific
if (now < cycle_last)
now = cycle_last;
for the other wrapping around clocksources, but TSC has
CLOCKSOURCE_MASK(64) which actually does not mask out anything so if
now is less than cycle_last the subtraction will give a negative
result. So we can check for that in clocksource_delta() and return 0
for that case.
Implement and enable it for x86
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: John Stultz <john.stultz@linaro.org>
diff --git a/kernel/time/timekeeping_internal.h b/kernel/time/timekeeping_internal.h
index 05dfa6b..4ea005a 100644
--- a/kernel/time/timekeeping_internal.h
+++ b/kernel/time/timekeeping_internal.h
@@ -12,9 +12,18 @@
#define tk_debug_account_sleep_time(x)
#endif
+#ifdef CONFIG_CLOCKSOURCE_VALIDATE_LAST_CYCLE
+static inline cycle_t clocksource_delta(cycle_t now, cycle_t last, cycle_t mask)
+{
+ cycle_t ret = (now - last) & mask;
+
+ return (s64) ret > 0 ? ret : 0;
+}
+#else
static inline cycle_t clocksource_delta(cycle_t now, cycle_t last, cycle_t mask)
{
return (now - last) & mask;
}
+#endif
#endif /* _TIMEKEEPING_INTERNAL_H */