diff options
| -rw-r--r-- | include/linux/clocksource.h | 2 | ||||
| -rw-r--r-- | kernel/time/clocksource.c | 11 | ||||
| -rw-r--r-- | kernel/time/timekeeping.c | 6 | ||||
| -rw-r--r-- | kernel/time/timekeeping_internal.h | 8 |
4 files changed, 20 insertions, 7 deletions
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h index ef1b16da6ad5..65b7c41471c3 100644 --- a/include/linux/clocksource.h +++ b/include/linux/clocksource.h @@ -49,6 +49,7 @@ struct module; * @archdata: Optional arch-specific data * @max_cycles: Maximum safe cycle value which won't overflow on * multiplication + * @max_raw_delta: Maximum safe delta value for negative motion detection * @name: Pointer to clocksource name * @list: List head for registration (internal) * @freq_khz: Clocksource frequency in khz. @@ -109,6 +110,7 @@ struct clocksource { struct arch_clocksource_data archdata; #endif u64 max_cycles; + u64 max_raw_delta; const char *name; struct list_head list; u32 freq_khz; diff --git a/kernel/time/clocksource.c b/kernel/time/clocksource.c index aab6472853fa..7304d7cf47f2 100644 --- a/kernel/time/clocksource.c +++ b/kernel/time/clocksource.c @@ -24,7 +24,7 @@ static void clocksource_enqueue(struct clocksource *cs); static noinline u64 cycles_to_nsec_safe(struct clocksource *cs, u64 start, u64 end) { - u64 delta = clocksource_delta(end, start, cs->mask); + u64 delta = clocksource_delta(end, start, cs->mask, cs->max_raw_delta); if (likely(delta < cs->max_cycles)) return clocksource_cyc2ns(delta, cs->mult, cs->shift); @@ -993,6 +993,15 @@ static inline void clocksource_update_max_deferment(struct clocksource *cs) cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift, cs->maxadj, cs->mask, &cs->max_cycles); + + /* + * Threshold for detecting negative motion in clocksource_delta(). + * + * Allow for 0.875 of the counter width so that overly long idle + * sleeps, which go slightly over mask/2, do not trigger the + * negative motion detection. + */ + cs->max_raw_delta = (cs->mask >> 1) + (cs->mask >> 2) + (cs->mask >> 3); } static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur) diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 0ca85ff4fbb4..3d128825d343 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -755,7 +755,8 @@ static void timekeeping_forward_now(struct timekeeper *tk) u64 cycle_now, delta; cycle_now = tk_clock_read(&tk->tkr_mono); - delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask); + delta = clocksource_delta(cycle_now, tk->tkr_mono.cycle_last, tk->tkr_mono.mask, + tk->tkr_mono.clock->max_raw_delta); tk->tkr_mono.cycle_last = cycle_now; tk->tkr_raw.cycle_last = cycle_now; @@ -2230,7 +2231,8 @@ static bool timekeeping_advance(enum timekeeping_adv_mode mode) return false; offset = clocksource_delta(tk_clock_read(&tk->tkr_mono), - tk->tkr_mono.cycle_last, tk->tkr_mono.mask); + tk->tkr_mono.cycle_last, tk->tkr_mono.mask, + tk->tkr_mono.clock->max_raw_delta); /* Check if there's really nothing to do */ if (offset < real_tk->cycle_interval && mode == TK_ADV_TICK) diff --git a/kernel/time/timekeeping_internal.h b/kernel/time/timekeeping_internal.h index 63e600e943a7..8c9079108ffb 100644 --- a/kernel/time/timekeeping_internal.h +++ b/kernel/time/timekeeping_internal.h @@ -30,15 +30,15 @@ static inline void timekeeping_inc_mg_floor_swaps(void) #endif -static inline u64 clocksource_delta(u64 now, u64 last, u64 mask) +static inline u64 clocksource_delta(u64 now, u64 last, u64 mask, u64 max_delta) { u64 ret = (now - last) & mask; /* - * Prevent time going backwards by checking the MSB of mask in - * the result. If set, return 0. + * Prevent time going backwards by checking the result against + * @max_delta. If greater, return 0. */ - return ret & ~(mask >> 1) ? 0 : ret; + return ret > max_delta ? 0 : ret; } /* Semi public for serialization of non timekeeper VDSO updates. */ |