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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 <tglx@linutronix.de>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Parit Bhargava <prarit@redhat.com>
Cc: Laurent Vivier <lvivier@redhat.com>
Cc: "Christopher S. Hall" <christopher.s.hall@intel.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com>
Cc: Richard Cochran <richardcochran@gmail.com>
Cc: Liav Rehana <liavr@mellanox.com>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/20161208204228.921674404@linutronix.de
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2016-12-08 20:49:38 +00:00
parent cbd99e3b28
commit c029a2bec6
1 changed files with 5 additions and 21 deletions
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26
kernel/time/timekeeping.c
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@ -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) {