system time variables
extern volatile time_t time_second;
extern volatile time_t time_uptime;
variable is the system's
“wall time” clock. It is set at boot by
, and is updated by
call and by periodic clock interrupts.
variable is a monotonically
increasing system clock. It is set at boot, and is updated by the periodic
timer interrupt. (It is not updated by
All of these variables contain times expressed in seconds since midnight (0
hour), January 1, 1970.
Clock interrupts should be blocked when reading or writing
, because those variables are
updated by hardclock(9)