| /* |
| * linux/kernel/time.c |
| * |
| * Copyright (C) 1991, 1992 Linus Torvalds |
| * |
| * This file contains the interface functions for the various |
| * time related system calls: time, stime, gettimeofday, settimeofday, |
| * adjtime |
| */ |
| /* |
| * Modification history kernel/time.c |
| * |
| * 1993-09-02 Philip Gladstone |
| * Created file with time related functions from sched.c and adjtimex() |
| * 1993-10-08 Torsten Duwe |
| * adjtime interface update and CMOS clock write code |
| * 1995-08-13 Torsten Duwe |
| * kernel PLL updated to 1994-12-13 specs (rfc-1589) |
| * 1999-01-16 Ulrich Windl |
| * Introduced error checking for many cases in adjtimex(). |
| * Updated NTP code according to technical memorandum Jan '96 |
| * "A Kernel Model for Precision Timekeeping" by Dave Mills |
| * Allow time_constant larger than MAXTC(6) for NTP v4 (MAXTC == 10) |
| * (Even though the technical memorandum forbids it) |
| * 2004-07-14 Christoph Lameter |
| * Added getnstimeofday to allow the posix timer functions to return |
| * with nanosecond accuracy |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/timex.h> |
| #include <linux/capability.h> |
| #include <linux/clocksource.h> |
| #include <linux/errno.h> |
| #include <linux/syscalls.h> |
| #include <linux/security.h> |
| #include <linux/fs.h> |
| #include <linux/slab.h> |
| #include <linux/math64.h> |
| #include <linux/ptrace.h> |
| |
| #include <asm/uaccess.h> |
| #include <asm/unistd.h> |
| |
| #include "timeconst.h" |
| |
| /* |
| * The timezone where the local system is located. Used as a default by some |
| * programs who obtain this value by using gettimeofday. |
| */ |
| struct timezone sys_tz; |
| |
| EXPORT_SYMBOL(sys_tz); |
| |
| #ifdef __ARCH_WANT_SYS_TIME |
| |
| /* |
| * sys_time() can be implemented in user-level using |
| * sys_gettimeofday(). Is this for backwards compatibility? If so, |
| * why not move it into the appropriate arch directory (for those |
| * architectures that need it). |
| */ |
| SYSCALL_DEFINE1(time, time_t __user *, tloc) |
| { |
| time_t i = get_seconds(); |
| |
| if (tloc) { |
| if (put_user(i,tloc)) |
| return -EFAULT; |
| } |
| force_successful_syscall_return(); |
| return i; |
| } |
| |
| /* |
| * sys_stime() can be implemented in user-level using |
| * sys_settimeofday(). Is this for backwards compatibility? If so, |
| * why not move it into the appropriate arch directory (for those |
| * architectures that need it). |
| */ |
| |
| SYSCALL_DEFINE1(stime, time_t __user *, tptr) |
| { |
| struct timespec tv; |
| int err; |
| |
| if (get_user(tv.tv_sec, tptr)) |
| return -EFAULT; |
| |
| tv.tv_nsec = 0; |
| |
| err = security_settime(&tv, NULL); |
| if (err) |
| return err; |
| |
| do_settimeofday(&tv); |
| return 0; |
| } |
| |
| #endif /* __ARCH_WANT_SYS_TIME */ |
| |
| SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv, |
| struct timezone __user *, tz) |
| { |
| if (likely(tv != NULL)) { |
| struct timeval ktv; |
| do_gettimeofday(&ktv); |
| if (copy_to_user(tv, &ktv, sizeof(ktv))) |
| return -EFAULT; |
| } |
| if (unlikely(tz != NULL)) { |
| if (copy_to_user(tz, &sys_tz, sizeof(sys_tz))) |
| return -EFAULT; |
| } |
| return 0; |
| } |
| |
| /* |
| * Adjust the time obtained from the CMOS to be UTC time instead of |
| * local time. |
| * |
| * This is ugly, but preferable to the alternatives. Otherwise we |
| * would either need to write a program to do it in /etc/rc (and risk |
| * confusion if the program gets run more than once; it would also be |
| * hard to make the program warp the clock precisely n hours) or |
| * compile in the timezone information into the kernel. Bad, bad.... |
| * |
| * - TYT, 1992-01-01 |
| * |
| * The best thing to do is to keep the CMOS clock in universal time (UTC) |
| * as real UNIX machines always do it. This avoids all headaches about |
| * daylight saving times and warping kernel clocks. |
| */ |
| static inline void warp_clock(void) |
| { |
| struct timespec delta, adjust; |
| delta.tv_sec = sys_tz.tz_minuteswest * 60; |
| delta.tv_nsec = 0; |
| adjust = timespec_add_safe(current_kernel_time(), delta); |
| do_settimeofday(&adjust); |
| } |
| |
| /* |
| * In case for some reason the CMOS clock has not already been running |
| * in UTC, but in some local time: The first time we set the timezone, |
| * we will warp the clock so that it is ticking UTC time instead of |
| * local time. Presumably, if someone is setting the timezone then we |
| * are running in an environment where the programs understand about |
| * timezones. This should be done at boot time in the /etc/rc script, |
| * as soon as possible, so that the clock can be set right. Otherwise, |
| * various programs will get confused when the clock gets warped. |
| */ |
| |
| int do_sys_settimeofday(struct timespec *tv, struct timezone *tz) |
| { |
| static int firsttime = 1; |
| int error = 0; |
| |
| if (tv && !timespec_valid(tv)) |
| return -EINVAL; |
| |
| error = security_settime(tv, tz); |
| if (error) |
| return error; |
| |
| if (tz) { |
| /* SMP safe, global irq locking makes it work. */ |
| sys_tz = *tz; |
| update_vsyscall_tz(); |
| if (firsttime) { |
| firsttime = 0; |
| if (!tv) |
| warp_clock(); |
| } |
| } |
| if (tv) |
| { |
| /* SMP safe, again the code in arch/foo/time.c should |
| * globally block out interrupts when it runs. |
| */ |
| return do_settimeofday(tv); |
| } |
| return 0; |
| } |
| |
| SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv, |
| struct timezone __user *, tz) |
| { |
| struct timeval user_tv; |
| struct timespec new_ts; |
| struct timezone new_tz; |
| |
| if (tv) { |
| if (copy_from_user(&user_tv, tv, sizeof(*tv))) |
| return -EFAULT; |
| new_ts.tv_sec = user_tv.tv_sec; |
| new_ts.tv_nsec = user_tv.tv_usec * NSEC_PER_USEC; |
| } |
| if (tz) { |
| if (copy_from_user(&new_tz, tz, sizeof(*tz))) |
| return -EFAULT; |
| } |
| |
| return do_sys_settimeofday(tv ? &new_ts : NULL, tz ? &new_tz : NULL); |
| } |
| |
| SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p) |
| { |
| struct timex txc; /* Local copy of parameter */ |
| int ret; |
| |
| /* Copy the user data space into the kernel copy |
| * structure. But bear in mind that the structures |
| * may change |
| */ |
| if(copy_from_user(&txc, txc_p, sizeof(struct timex))) |
| return -EFAULT; |
| ret = do_adjtimex(&txc); |
| return copy_to_user(txc_p, &txc, sizeof(struct timex)) ? -EFAULT : ret; |
| } |
| |
| /** |
| * current_fs_time - Return FS time |
| * @sb: Superblock. |
| * |
| * Return the current time truncated to the time granularity supported by |
| * the fs. |
| */ |
| struct timespec current_fs_time(struct super_block *sb) |
| { |
| struct timespec now = current_kernel_time(); |
| return timespec_trunc(now, sb->s_time_gran); |
| } |
| EXPORT_SYMBOL(current_fs_time); |
| |
| /* |
| * Convert jiffies to milliseconds and back. |
| * |
| * Avoid unnecessary multiplications/divisions in the |
| * two most common HZ cases: |
| */ |
| unsigned int inline jiffies_to_msecs(const unsigned long j) |
| { |
| #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) |
| return (MSEC_PER_SEC / HZ) * j; |
| #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) |
| return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC); |
| #else |
| # if BITS_PER_LONG == 32 |
| return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32; |
| # else |
| return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN; |
| # endif |
| #endif |
| } |
| EXPORT_SYMBOL(jiffies_to_msecs); |
| |
| unsigned int inline jiffies_to_usecs(const unsigned long j) |
| { |
| #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ) |
| return (USEC_PER_SEC / HZ) * j; |
| #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC) |
| return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC); |
| #else |
| # if BITS_PER_LONG == 32 |
| return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32; |
| # else |
| return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN; |
| # endif |
| #endif |
| } |
| EXPORT_SYMBOL(jiffies_to_usecs); |
| |
| /** |
| * timespec_trunc - Truncate timespec to a granularity |
| * @t: Timespec |
| * @gran: Granularity in ns. |
| * |
| * Truncate a timespec to a granularity. gran must be smaller than a second. |
| * Always rounds down. |
| * |
| * This function should be only used for timestamps returned by |
| * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because |
| * it doesn't handle the better resolution of the latter. |
| */ |
| struct timespec timespec_trunc(struct timespec t, unsigned gran) |
| { |
| /* |
| * Division is pretty slow so avoid it for common cases. |
| * Currently current_kernel_time() never returns better than |
| * jiffies resolution. Exploit that. |
| */ |
| if (gran <= jiffies_to_usecs(1) * 1000) { |
| /* nothing */ |
| } else if (gran == 1000000000) { |
| t.tv_nsec = 0; |
| } else { |
| t.tv_nsec -= t.tv_nsec % gran; |
| } |
| return t; |
| } |
| EXPORT_SYMBOL(timespec_trunc); |
| |
| #ifndef CONFIG_GENERIC_TIME |
| /* |
| * Simulate gettimeofday using do_gettimeofday which only allows a timeval |
| * and therefore only yields usec accuracy |
| */ |
| void getnstimeofday(struct timespec *tv) |
| { |
| struct timeval x; |
| |
| do_gettimeofday(&x); |
| tv->tv_sec = x.tv_sec; |
| tv->tv_nsec = x.tv_usec * NSEC_PER_USEC; |
| } |
| EXPORT_SYMBOL_GPL(getnstimeofday); |
| #endif |
| |
| /* Converts Gregorian date to seconds since 1970-01-01 00:00:00. |
| * Assumes input in normal date format, i.e. 1980-12-31 23:59:59 |
| * => year=1980, mon=12, day=31, hour=23, min=59, sec=59. |
| * |
| * [For the Julian calendar (which was used in Russia before 1917, |
| * Britain & colonies before 1752, anywhere else before 1582, |
| * and is still in use by some communities) leave out the |
| * -year/100+year/400 terms, and add 10.] |
| * |
| * This algorithm was first published by Gauss (I think). |
| * |
| * WARNING: this function will overflow on 2106-02-07 06:28:16 on |
| * machines where long is 32-bit! (However, as time_t is signed, we |
| * will already get problems at other places on 2038-01-19 03:14:08) |
| */ |
| unsigned long |
| mktime(const unsigned int year0, const unsigned int mon0, |
| const unsigned int day, const unsigned int hour, |
| const unsigned int min, const unsigned int sec) |
| { |
| unsigned int mon = mon0, year = year0; |
| |
| /* 1..12 -> 11,12,1..10 */ |
| if (0 >= (int) (mon -= 2)) { |
| mon += 12; /* Puts Feb last since it has leap day */ |
| year -= 1; |
| } |
| |
| return ((((unsigned long) |
| (year/4 - year/100 + year/400 + 367*mon/12 + day) + |
| year*365 - 719499 |
| )*24 + hour /* now have hours */ |
| )*60 + min /* now have minutes */ |
| )*60 + sec; /* finally seconds */ |
| } |
| |
| EXPORT_SYMBOL(mktime); |
| |
| /** |
| * set_normalized_timespec - set timespec sec and nsec parts and normalize |
| * |
| * @ts: pointer to timespec variable to be set |
| * @sec: seconds to set |
| * @nsec: nanoseconds to set |
| * |
| * Set seconds and nanoseconds field of a timespec variable and |
| * normalize to the timespec storage format |
| * |
| * Note: The tv_nsec part is always in the range of |
| * 0 <= tv_nsec < NSEC_PER_SEC |
| * For negative values only the tv_sec field is negative ! |
| */ |
| void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec) |
| { |
| while (nsec >= NSEC_PER_SEC) { |
| /* |
| * The following asm() prevents the compiler from |
| * optimising this loop into a modulo operation. See |
| * also __iter_div_u64_rem() in include/linux/time.h |
| */ |
| asm("" : "+rm"(nsec)); |
| nsec -= NSEC_PER_SEC; |
| ++sec; |
| } |
| while (nsec < 0) { |
| asm("" : "+rm"(nsec)); |
| nsec += NSEC_PER_SEC; |
| --sec; |
| } |
| ts->tv_sec = sec; |
| ts->tv_nsec = nsec; |
| } |
| EXPORT_SYMBOL(set_normalized_timespec); |
| |
| /** |
| * ns_to_timespec - Convert nanoseconds to timespec |
| * @nsec: the nanoseconds value to be converted |
| * |
| * Returns the timespec representation of the nsec parameter. |
| */ |
| struct timespec ns_to_timespec(const s64 nsec) |
| { |
| struct timespec ts; |
| s32 rem; |
| |
| if (!nsec) |
| return (struct timespec) {0, 0}; |
| |
| ts.tv_sec = div_s64_rem(nsec, NSEC_PER_SEC, &rem); |
| if (unlikely(rem < 0)) { |
| ts.tv_sec--; |
| rem += NSEC_PER_SEC; |
| } |
| ts.tv_nsec = rem; |
| |
| return ts; |
| } |
| EXPORT_SYMBOL(ns_to_timespec); |
| |
| /** |
| * ns_to_timeval - Convert nanoseconds to timeval |
| * @nsec: the nanoseconds value to be converted |
| * |
| * Returns the timeval representation of the nsec parameter. |
| */ |
| struct timeval ns_to_timeval(const s64 nsec) |
| { |
| struct timespec ts = ns_to_timespec(nsec); |
| struct timeval tv; |
| |
| tv.tv_sec = ts.tv_sec; |
| tv.tv_usec = (suseconds_t) ts.tv_nsec / 1000; |
| |
| return tv; |
| } |
| EXPORT_SYMBOL(ns_to_timeval); |
| |
| /* |
| * When we convert to jiffies then we interpret incoming values |
| * the following way: |
| * |
| * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET) |
| * |
| * - 'too large' values [that would result in larger than |
| * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. |
| * |
| * - all other values are converted to jiffies by either multiplying |
| * the input value by a factor or dividing it with a factor |
| * |
| * We must also be careful about 32-bit overflows. |
| */ |
| unsigned long msecs_to_jiffies(const unsigned int m) |
| { |
| /* |
| * Negative value, means infinite timeout: |
| */ |
| if ((int)m < 0) |
| return MAX_JIFFY_OFFSET; |
| |
| #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) |
| /* |
| * HZ is equal to or smaller than 1000, and 1000 is a nice |
| * round multiple of HZ, divide with the factor between them, |
| * but round upwards: |
| */ |
| return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ); |
| #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) |
| /* |
| * HZ is larger than 1000, and HZ is a nice round multiple of |
| * 1000 - simply multiply with the factor between them. |
| * |
| * But first make sure the multiplication result cannot |
| * overflow: |
| */ |
| if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) |
| return MAX_JIFFY_OFFSET; |
| |
| return m * (HZ / MSEC_PER_SEC); |
| #else |
| /* |
| * Generic case - multiply, round and divide. But first |
| * check that if we are doing a net multiplication, that |
| * we wouldn't overflow: |
| */ |
| if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) |
| return MAX_JIFFY_OFFSET; |
| |
| return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) |
| >> MSEC_TO_HZ_SHR32; |
| #endif |
| } |
| EXPORT_SYMBOL(msecs_to_jiffies); |
| |
| unsigned long usecs_to_jiffies(const unsigned int u) |
| { |
| if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET)) |
| return MAX_JIFFY_OFFSET; |
| #if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ) |
| return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ); |
| #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC) |
| return u * (HZ / USEC_PER_SEC); |
| #else |
| return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32) |
| >> USEC_TO_HZ_SHR32; |
| #endif |
| } |
| EXPORT_SYMBOL(usecs_to_jiffies); |
| |
| /* |
| * The TICK_NSEC - 1 rounds up the value to the next resolution. Note |
| * that a remainder subtract here would not do the right thing as the |
| * resolution values don't fall on second boundries. I.e. the line: |
| * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding. |
| * |
| * Rather, we just shift the bits off the right. |
| * |
| * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec |
| * value to a scaled second value. |
| */ |
| unsigned long |
| timespec_to_jiffies(const struct timespec *value) |
| { |
| unsigned long sec = value->tv_sec; |
| long nsec = value->tv_nsec + TICK_NSEC - 1; |
| |
| if (sec >= MAX_SEC_IN_JIFFIES){ |
| sec = MAX_SEC_IN_JIFFIES; |
| nsec = 0; |
| } |
| return (((u64)sec * SEC_CONVERSION) + |
| (((u64)nsec * NSEC_CONVERSION) >> |
| (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC; |
| |
| } |
| EXPORT_SYMBOL(timespec_to_jiffies); |
| |
| void |
| jiffies_to_timespec(const unsigned long jiffies, struct timespec *value) |
| { |
| /* |
| * Convert jiffies to nanoseconds and separate with |
| * one divide. |
| */ |
| u32 rem; |
| value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, |
| NSEC_PER_SEC, &rem); |
| value->tv_nsec = rem; |
| } |
| EXPORT_SYMBOL(jiffies_to_timespec); |
| |
| /* Same for "timeval" |
| * |
| * Well, almost. The problem here is that the real system resolution is |
| * in nanoseconds and the value being converted is in micro seconds. |
| * Also for some machines (those that use HZ = 1024, in-particular), |
| * there is a LARGE error in the tick size in microseconds. |
| |
| * The solution we use is to do the rounding AFTER we convert the |
| * microsecond part. Thus the USEC_ROUND, the bits to be shifted off. |
| * Instruction wise, this should cost only an additional add with carry |
| * instruction above the way it was done above. |
| */ |
| unsigned long |
| timeval_to_jiffies(const struct timeval *value) |
| { |
| unsigned long sec = value->tv_sec; |
| long usec = value->tv_usec; |
| |
| if (sec >= MAX_SEC_IN_JIFFIES){ |
| sec = MAX_SEC_IN_JIFFIES; |
| usec = 0; |
| } |
| return (((u64)sec * SEC_CONVERSION) + |
| (((u64)usec * USEC_CONVERSION + USEC_ROUND) >> |
| (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC; |
| } |
| EXPORT_SYMBOL(timeval_to_jiffies); |
| |
| void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value) |
| { |
| /* |
| * Convert jiffies to nanoseconds and separate with |
| * one divide. |
| */ |
| u32 rem; |
| |
| value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, |
| NSEC_PER_SEC, &rem); |
| value->tv_usec = rem / NSEC_PER_USEC; |
| } |
| EXPORT_SYMBOL(jiffies_to_timeval); |
| |
| /* |
| * Convert jiffies/jiffies_64 to clock_t and back. |
| */ |
| clock_t jiffies_to_clock_t(long x) |
| { |
| #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 |
| # if HZ < USER_HZ |
| return x * (USER_HZ / HZ); |
| # else |
| return x / (HZ / USER_HZ); |
| # endif |
| #else |
| return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ); |
| #endif |
| } |
| EXPORT_SYMBOL(jiffies_to_clock_t); |
| |
| unsigned long clock_t_to_jiffies(unsigned long x) |
| { |
| #if (HZ % USER_HZ)==0 |
| if (x >= ~0UL / (HZ / USER_HZ)) |
| return ~0UL; |
| return x * (HZ / USER_HZ); |
| #else |
| /* Don't worry about loss of precision here .. */ |
| if (x >= ~0UL / HZ * USER_HZ) |
| return ~0UL; |
| |
| /* .. but do try to contain it here */ |
| return div_u64((u64)x * HZ, USER_HZ); |
| #endif |
| } |
| EXPORT_SYMBOL(clock_t_to_jiffies); |
| |
| u64 jiffies_64_to_clock_t(u64 x) |
| { |
| #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 |
| # if HZ < USER_HZ |
| x = div_u64(x * USER_HZ, HZ); |
| # elif HZ > USER_HZ |
| x = div_u64(x, HZ / USER_HZ); |
| # else |
| /* Nothing to do */ |
| # endif |
| #else |
| /* |
| * There are better ways that don't overflow early, |
| * but even this doesn't overflow in hundreds of years |
| * in 64 bits, so.. |
| */ |
| x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ)); |
| #endif |
| return x; |
| } |
| EXPORT_SYMBOL(jiffies_64_to_clock_t); |
| |
| u64 nsec_to_clock_t(u64 x) |
| { |
| #if (NSEC_PER_SEC % USER_HZ) == 0 |
| return div_u64(x, NSEC_PER_SEC / USER_HZ); |
| #elif (USER_HZ % 512) == 0 |
| return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512); |
| #else |
| /* |
| * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024, |
| * overflow after 64.99 years. |
| * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ... |
| */ |
| return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ); |
| #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) |
| { |
| unsigned long seq; |
| u64 ret; |
| |
| do { |
| seq = read_seqbegin(&xtime_lock); |
| ret = jiffies_64; |
| } while (read_seqretry(&xtime_lock, seq)); |
| return ret; |
| } |
| EXPORT_SYMBOL(get_jiffies_64); |
| #endif |
| |
| EXPORT_SYMBOL(jiffies); |
| |
| /* |
| * Add two timespec values and do a safety check for overflow. |
| * It's assumed that both values are valid (>= 0) |
| */ |
| struct timespec timespec_add_safe(const struct timespec lhs, |
| const struct timespec rhs) |
| { |
| struct timespec res; |
| |
| set_normalized_timespec(&res, lhs.tv_sec + rhs.tv_sec, |
| lhs.tv_nsec + rhs.tv_nsec); |
| |
| if (res.tv_sec < lhs.tv_sec || res.tv_sec < rhs.tv_sec) |
| res.tv_sec = TIME_T_MAX; |
| |
| return res; |
| } |