diff options
author | Thomas Gleixner <tglx@linutronix.de> | 2010-02-17 18:27:37 +0100 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2010-02-17 18:28:05 +0100 |
commit | b7e56edba4b02f2079042c326a8cd72a44635817 (patch) | |
tree | b5042002e9747cd8fb1278d61f86d8b92a74c018 /kernel/time.c | |
parent | 13ca0fcaa33f6b1984c4111b6ec5df42689fea6f (diff) | |
parent | b0483e78e5c4c9871fc5541875b3bc006846d46b (diff) |
Merge branch 'linus' into x86/mm
x86/mm is on 32-rc4 and missing the spinlock namespace changes which
are needed for further commits into this topic.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time.c')
-rw-r--r-- | kernel/time.c | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/kernel/time.c b/kernel/time.c index 2e2e469a7fe..804798005d1 100644 --- a/kernel/time.c +++ b/kernel/time.c @@ -662,6 +662,36 @@ u64 nsec_to_clock_t(u64 x) #endif } +/** + * nsecs_to_jiffies - Convert nsecs in u64 to jiffies + * + * @n: nsecs in u64 + * + * Unlike {m,u}secs_to_jiffies, type of input is not unsigned int but u64. + * And this doesn't return MAX_JIFFY_OFFSET since this function is designed + * for scheduler, not for use in device drivers to calculate timeout value. + * + * note: + * NSEC_PER_SEC = 10^9 = (5^9 * 2^9) = (1953125 * 512) + * ULLONG_MAX ns = 18446744073.709551615 secs = about 584 years + */ +unsigned long nsecs_to_jiffies(u64 n) +{ +#if (NSEC_PER_SEC % HZ) == 0 + /* Common case, HZ = 100, 128, 200, 250, 256, 500, 512, 1000 etc. */ + return div_u64(n, NSEC_PER_SEC / HZ); +#elif (HZ % 512) == 0 + /* overflow after 292 years if HZ = 1024 */ + return div_u64(n * HZ / 512, NSEC_PER_SEC / 512); +#else + /* + * Generic case - optimized for cases where HZ is a multiple of 3. + * overflow after 64.99 years, exact for HZ = 60, 72, 90, 120 etc. + */ + return div_u64(n * 9, (9ull * NSEC_PER_SEC + HZ / 2) / HZ); +#endif +} + #if (BITS_PER_LONG < 64) u64 get_jiffies_64(void) { |