Messages in this thread | | | Date | Thu, 1 Nov 2007 15:29:14 +0000 | From | Ralf Baechle <> | Subject | CLOCK_TICK_RATE in NTP code |
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kernel/time/ntp.c contains the following piece of code:
#define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE) #define CLOCK_TICK_ADJUST (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / \ (s64)CLOCK_TICK_RATE)
static void ntp_update_frequency(void) { u64 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT; second_length += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT; second_length += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC);
tick_length_base = second_length;
do_div(second_length, HZ); tick_nsec = second_length >> TICK_LENGTH_SHIFT;
do_div(tick_length_base, NTP_INTERVAL_FREQ); }
So it uses CLOCK_TICK_RATE which on many systems but not all is defined to the i8253 input clock. But timekeeping on anything remotely modern makes little use of the i8253 so I wonder the intent was here.
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