From c029a2bec66e42e57538cb65e28618baf6a4b311 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Thu, 8 Dec 2016 20:49:38 +0000 Subject: [PATCH] timekeeping: Use mul_u64_u32_shr() instead of open coding it The resume code must deal with a clocksource delta which is potentially big enough to overflow the 64bit mult. Replace the open coded handling with the proper function. Signed-off-by: Thomas Gleixner Reviewed-by: David Gibson Acked-by: Peter Zijlstra (Intel) Cc: Parit Bhargava Cc: Laurent Vivier Cc: "Christopher S. Hall" Cc: Chris Metcalf Cc: Richard Cochran Cc: Liav Rehana Cc: John Stultz Link: http://lkml.kernel.org/r/20161208204228.921674404@linutronix.de Signed-off-by: Thomas Gleixner --- kernel/time/timekeeping.c | 26 +++++--------------------- 1 file changed, 5 insertions(+), 21 deletions(-) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 82e1b5cbebbb..da233cdf89b0 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -1644,7 +1644,7 @@ void timekeeping_resume(void) struct clocksource *clock = tk->tkr_mono.clock; unsigned long flags; struct timespec64 ts_new, ts_delta; - cycle_t cycle_now, cycle_delta; + cycle_t cycle_now; sleeptime_injected = false; read_persistent_clock64(&ts_new); @@ -1670,27 +1670,11 @@ void timekeeping_resume(void) cycle_now = tk->tkr_mono.read(clock); if ((clock->flags & CLOCK_SOURCE_SUSPEND_NONSTOP) && cycle_now > tk->tkr_mono.cycle_last) { - u64 num, max = ULLONG_MAX; - u32 mult = clock->mult; - u32 shift = clock->shift; - s64 nsec = 0; - - cycle_delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, - tk->tkr_mono.mask); - - /* - * "cycle_delta * mutl" may cause 64 bits overflow, if the - * suspended time is too long. In that case we need do the - * 64 bits math carefully - */ - do_div(max, mult); - if (cycle_delta > max) { - num = div64_u64(cycle_delta, max); - nsec = (((u64) max * mult) >> shift) * num; - cycle_delta -= num * max; - } - nsec += ((u64) cycle_delta * mult) >> shift; + u64 nsec, cyc_delta; + cyc_delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, + tk->tkr_mono.mask); + nsec = mul_u64_u32_shr(cyc_delta, clock->mult, clock->shift); ts_delta = ns_to_timespec64(nsec); sleeptime_injected = true; } else if (timespec64_compare(&ts_new, &timekeeping_suspend_time) > 0) { -- 2.20.1