diff options
| -rw-r--r-- | include/linux/delay.h | 29 |
1 files changed, 25 insertions, 4 deletions
diff --git a/include/linux/delay.h b/include/linux/delay.h index 2de509e4adce..89866bab100d 100644 --- a/include/linux/delay.h +++ b/include/linux/delay.h @@ -11,6 +11,7 @@ #include <linux/math.h> #include <linux/sched.h> +#include <linux/jiffies.h> extern unsigned long loops_per_jiffy; @@ -102,15 +103,35 @@ static inline void ssleep(unsigned int seconds) msleep(seconds * 1000); } -/* see Documentation/timers/timers-howto.rst for the thresholds */ +static const unsigned int max_slack_shift = 2; +#define USLEEP_RANGE_UPPER_BOUND ((TICK_NSEC << max_slack_shift) / NSEC_PER_USEC) + +/** + * fsleep - flexible sleep which autoselects the best mechanism + * @usecs: requested sleep duration in microseconds + * + * flseep() selects the best mechanism that will provide maximum 25% slack + * to the requested sleep duration. Therefore it uses: + * + * * udelay() loop for sleep durations <= 10 microseconds to avoid hrtimer + * overhead for really short sleep durations. + * * usleep_range() for sleep durations which would lead with the usage of + * msleep() to a slack larger than 25%. This depends on the granularity of + * jiffies. + * * msleep() for all other sleep durations. + * + * Note: When %CONFIG_HIGH_RES_TIMERS is not set, all sleeps are processed with + * the granularity of jiffies and the slack might exceed 25% especially for + * short sleep durations. + */ static inline void fsleep(unsigned long usecs) { if (usecs <= 10) udelay(usecs); - else if (usecs <= 20000) - usleep_range(usecs, 2 * usecs); + else if (usecs < USLEEP_RANGE_UPPER_BOUND) + usleep_range(usecs, usecs + (usecs >> max_slack_shift)); else - msleep(DIV_ROUND_UP(usecs, 1000)); + msleep(DIV_ROUND_UP(usecs, USEC_PER_MSEC)); } #endif /* defined(_LINUX_DELAY_H) */ |