diff --git a/include/linux/timer.h b/include/linux/timer.h index d4ba79248a27..daf9685b861c 100644 --- a/include/linux/timer.h +++ b/include/linux/timer.h @@ -186,4 +186,9 @@ unsigned long __round_jiffies_relative(unsigned long j, int cpu); unsigned long round_jiffies(unsigned long j); unsigned long round_jiffies_relative(unsigned long j); +unsigned long __round_jiffies_up(unsigned long j, int cpu); +unsigned long __round_jiffies_up_relative(unsigned long j, int cpu); +unsigned long round_jiffies_up(unsigned long j); +unsigned long round_jiffies_up_relative(unsigned long j); + #endif diff --git a/kernel/timer.c b/kernel/timer.c index 56becf373c58..dbd50fabe4c7 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -112,6 +112,44 @@ timer_set_base(struct timer_list *timer, struct tvec_base *new_base) tbase_get_deferrable(timer->base)); } +static unsigned long round_jiffies_common(unsigned long j, int cpu, + bool force_up) +{ + int rem; + unsigned long original = j; + + /* + * We don't want all cpus firing their timers at once hitting the + * same lock or cachelines, so we skew each extra cpu with an extra + * 3 jiffies. This 3 jiffies came originally from the mm/ code which + * already did this. + * The skew is done by adding 3*cpunr, then round, then subtract this + * extra offset again. + */ + j += cpu * 3; + + rem = j % HZ; + + /* + * If the target jiffie is just after a whole second (which can happen + * due to delays of the timer irq, long irq off times etc etc) then + * we should round down to the whole second, not up. Use 1/4th second + * as cutoff for this rounding as an extreme upper bound for this. + * But never round down if @force_up is set. + */ + if (rem < HZ/4 && !force_up) /* round down */ + j = j - rem; + else /* round up */ + j = j - rem + HZ; + + /* now that we have rounded, subtract the extra skew again */ + j -= cpu * 3; + + if (j <= jiffies) /* rounding ate our timeout entirely; */ + return original; + return j; +} + /** * __round_jiffies - function to round jiffies to a full second * @j: the time in (absolute) jiffies that should be rounded @@ -134,38 +172,7 @@ timer_set_base(struct timer_list *timer, struct tvec_base *new_base) */ unsigned long __round_jiffies(unsigned long j, int cpu) { - int rem; - unsigned long original = j; - - /* - * We don't want all cpus firing their timers at once hitting the - * same lock or cachelines, so we skew each extra cpu with an extra - * 3 jiffies. This 3 jiffies came originally from the mm/ code which - * already did this. - * The skew is done by adding 3*cpunr, then round, then subtract this - * extra offset again. - */ - j += cpu * 3; - - rem = j % HZ; - - /* - * If the target jiffie is just after a whole second (which can happen - * due to delays of the timer irq, long irq off times etc etc) then - * we should round down to the whole second, not up. Use 1/4th second - * as cutoff for this rounding as an extreme upper bound for this. - */ - if (rem < HZ/4) /* round down */ - j = j - rem; - else /* round up */ - j = j - rem + HZ; - - /* now that we have rounded, subtract the extra skew again */ - j -= cpu * 3; - - if (j <= jiffies) /* rounding ate our timeout entirely; */ - return original; - return j; + return round_jiffies_common(j, cpu, false); } EXPORT_SYMBOL_GPL(__round_jiffies); @@ -191,13 +198,10 @@ EXPORT_SYMBOL_GPL(__round_jiffies); */ unsigned long __round_jiffies_relative(unsigned long j, int cpu) { - /* - * In theory the following code can skip a jiffy in case jiffies - * increments right between the addition and the later subtraction. - * However since the entire point of this function is to use approximate - * timeouts, it's entirely ok to not handle that. - */ - return __round_jiffies(j + jiffies, cpu) - jiffies; + unsigned long j0 = jiffies; + + /* Use j0 because jiffies might change while we run */ + return round_jiffies_common(j + j0, cpu, false) - j0; } EXPORT_SYMBOL_GPL(__round_jiffies_relative); @@ -218,7 +222,7 @@ EXPORT_SYMBOL_GPL(__round_jiffies_relative); */ unsigned long round_jiffies(unsigned long j) { - return __round_jiffies(j, raw_smp_processor_id()); + return round_jiffies_common(j, raw_smp_processor_id(), false); } EXPORT_SYMBOL_GPL(round_jiffies); @@ -243,6 +247,71 @@ unsigned long round_jiffies_relative(unsigned long j) } EXPORT_SYMBOL_GPL(round_jiffies_relative); +/** + * __round_jiffies_up - function to round jiffies up to a full second + * @j: the time in (absolute) jiffies that should be rounded + * @cpu: the processor number on which the timeout will happen + * + * This is the same as __round_jiffies() except that it will never + * round down. This is useful for timeouts for which the exact time + * of firing does not matter too much, as long as they don't fire too + * early. + */ +unsigned long __round_jiffies_up(unsigned long j, int cpu) +{ + return round_jiffies_common(j, cpu, true); +} +EXPORT_SYMBOL_GPL(__round_jiffies_up); + +/** + * __round_jiffies_up_relative - function to round jiffies up to a full second + * @j: the time in (relative) jiffies that should be rounded + * @cpu: the processor number on which the timeout will happen + * + * This is the same as __round_jiffies_relative() except that it will never + * round down. This is useful for timeouts for which the exact time + * of firing does not matter too much, as long as they don't fire too + * early. + */ +unsigned long __round_jiffies_up_relative(unsigned long j, int cpu) +{ + unsigned long j0 = jiffies; + + /* Use j0 because jiffies might change while we run */ + return round_jiffies_common(j + j0, cpu, true) - j0; +} +EXPORT_SYMBOL_GPL(__round_jiffies_up_relative); + +/** + * round_jiffies_up - function to round jiffies up to a full second + * @j: the time in (absolute) jiffies that should be rounded + * + * This is the same as round_jiffies() except that it will never + * round down. This is useful for timeouts for which the exact time + * of firing does not matter too much, as long as they don't fire too + * early. + */ +unsigned long round_jiffies_up(unsigned long j) +{ + return round_jiffies_common(j, raw_smp_processor_id(), true); +} +EXPORT_SYMBOL_GPL(round_jiffies_up); + +/** + * round_jiffies_up_relative - function to round jiffies up to a full second + * @j: the time in (relative) jiffies that should be rounded + * + * This is the same as round_jiffies_relative() except that it will never + * round down. This is useful for timeouts for which the exact time + * of firing does not matter too much, as long as they don't fire too + * early. + */ +unsigned long round_jiffies_up_relative(unsigned long j) +{ + return __round_jiffies_up_relative(j, raw_smp_processor_id()); +} +EXPORT_SYMBOL_GPL(round_jiffies_up_relative); + static inline void set_running_timer(struct tvec_base *base, struct timer_list *timer)