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kernel/time.c
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/* * 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 |
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* |
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* 1993-09-02 Philip Gladstone |
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* Created file with time related functions from sched.c and adjtimex() |
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* 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> |
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#include <linux/capability.h> |
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#include <linux/clocksource.h> |
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#include <linux/errno.h> |
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#include <linux/syscalls.h> #include <linux/security.h> #include <linux/fs.h> |
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#include <linux/math64.h> |
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#include <linux/ptrace.h> |
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#include <asm/uaccess.h> #include <asm/unistd.h> |
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#include "timeconst.h" |
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/* |
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* 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). */ |
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SYSCALL_DEFINE1(time, time_t __user *, tloc) |
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{ |
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time_t i = get_seconds(); |
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if (tloc) { |
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if (put_user(i,tloc)) |
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return -EFAULT; |
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} |
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force_successful_syscall_return(); |
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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). */ |
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SYSCALL_DEFINE1(stime, time_t __user *, tptr) |
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{ 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 */ |
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SYSCALL_DEFINE2(gettimeofday, struct timeval __user *, tv, struct timezone __user *, tz) |
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{ 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. |
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* |
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* 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 |
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* confusion if the program gets run more than once; it would also be |
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* hard to make the program warp the clock precisely n hours) or * compile in the timezone information into the kernel. Bad, bad.... * |
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* - TYT, 1992-01-01 |
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* * 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. */ |
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static inline void warp_clock(void) |
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{ |
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struct timespec adjust; adjust = current_kernel_time(); adjust.tv_sec += sys_tz.tz_minuteswest * 60; |
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do_settimeofday(&adjust); |
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} /* * 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; |
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if (tv && !timespec_valid(tv)) |
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return -EINVAL; |
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error = security_settime(tv, tz); if (error) return error; if (tz) { /* SMP safe, global irq locking makes it work. */ sys_tz = *tz; |
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update_vsyscall_tz(); |
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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; } |
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SYSCALL_DEFINE2(settimeofday, struct timeval __user *, tv, struct timezone __user *, tz) |
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{ 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); } |
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SYSCALL_DEFINE1(adjtimex, struct timex __user *, txc_p) |
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{ 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; } |
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/** * current_fs_time - Return FS time * @sb: Superblock. * |
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* Return the current time truncated to the time granularity supported by |
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* 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); |
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/* * 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 |
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# if BITS_PER_LONG == 32 |
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return (HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32; |
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# else return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN; # endif |
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#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 |
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# if BITS_PER_LONG == 32 |
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return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32; |
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# else return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN; # endif |
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#endif } EXPORT_SYMBOL(jiffies_to_usecs); |
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/** |
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* timespec_trunc - Truncate timespec to a granularity |
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* @t: Timespec |
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* @gran: Granularity in ns. |
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* |
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* Truncate a timespec to a granularity. gran must be smaller than a second. |
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* Always rounds down. * * This function should be only used for timestamps returned by * current_kernel_time() or CURRENT_TIME, not with do_gettimeofday() because |
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* it doesn't handle the better resolution of the latter. |
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*/ 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); |
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/* 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 |
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* machines where long is 32-bit! (However, as time_t is signed, we |
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* will already get problems at other places on 2038-01-19 03:14:08) */ unsigned long |
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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) |
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{ |
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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 */ |
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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 */ } |
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EXPORT_SYMBOL(mktime); |
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/** * 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 |
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* 0 <= tv_nsec < NSEC_PER_SEC |
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* For negative values only the tv_sec field is negative ! */ |
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void set_normalized_timespec(struct timespec *ts, time_t sec, s64 nsec) |
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{ while (nsec >= NSEC_PER_SEC) { |
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/* * 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)); |
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nsec -= NSEC_PER_SEC; ++sec; } while (nsec < 0) { |
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asm("" : "+rm"(nsec)); |
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nsec += NSEC_PER_SEC; --sec; } ts->tv_sec = sec; ts->tv_nsec = nsec; } |
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EXPORT_SYMBOL(set_normalized_timespec); |
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/** * ns_to_timespec - Convert nanoseconds to timespec * @nsec: the nanoseconds value to be converted * * Returns the timespec representation of the nsec parameter. */ |
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struct timespec ns_to_timespec(const s64 nsec) |
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{ struct timespec ts; |
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s32 rem; |
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|
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if (!nsec) return (struct timespec) {0, 0}; |
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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; |
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return ts; } |
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EXPORT_SYMBOL(ns_to_timespec); |
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/** * ns_to_timeval - Convert nanoseconds to timeval * @nsec: the nanoseconds value to be converted * * Returns the timeval representation of the nsec parameter. */ |
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struct timeval ns_to_timeval(const s64 nsec) |
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{ 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; } |
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EXPORT_SYMBOL(ns_to_timeval); |
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/* |
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* 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. */ |
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unsigned long msecs_to_jiffies(const unsigned int m) { |
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/* * Negative value, means infinite timeout: */ if ((int)m < 0) |
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return MAX_JIFFY_OFFSET; |
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|
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#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) |
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/* * 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: */ |
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return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ); #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) |
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/* * 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; |
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return m * (HZ / MSEC_PER_SEC); #else |
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/* * Generic case - multiply, round and divide. But first * check that if we are doing a net multiplication, that |
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*/ if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) return MAX_JIFFY_OFFSET; |
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return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) |
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>> MSEC_TO_HZ_SHR32; |
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#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 |
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return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32) |
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>> USEC_TO_HZ_SHR32; |
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#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. */ |
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u32 rem; value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, NSEC_PER_SEC, &rem); value->tv_nsec = rem; |
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} 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; } |
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EXPORT_SYMBOL(timeval_to_jiffies); |
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void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value) { /* * Convert jiffies to nanoseconds and separate with * one divide. */ |
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u32 rem; |
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value->tv_sec = div_u64_rem((u64)jiffies * TICK_NSEC, NSEC_PER_SEC, &rem); value->tv_usec = rem / NSEC_PER_USEC; |
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} |
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EXPORT_SYMBOL(jiffies_to_timeval); |
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/* * 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 |
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# if HZ < USER_HZ return x * (USER_HZ / HZ); # else |
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return x / (HZ / USER_HZ); |
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# endif |
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#else |
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return div_u64((u64)x * TICK_NSEC, NSEC_PER_SEC / USER_HZ); |
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#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 |
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/* Don't worry about loss of precision here .. */ if (x >= ~0UL / HZ * USER_HZ) return ~0UL; /* .. but do try to contain it here */ |
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return div_u64((u64)x * HZ, USER_HZ); |
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#endif } EXPORT_SYMBOL(clock_t_to_jiffies); u64 jiffies_64_to_clock_t(u64 x) { #if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 |
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# if HZ < USER_HZ |
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x = div_u64(x * USER_HZ, HZ); |
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# elif HZ > USER_HZ |
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x = div_u64(x, HZ / USER_HZ); |
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# else /* Nothing to do */ |
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# endif |
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#else /* * There are better ways that don't overflow early, * but even this doesn't overflow in hundreds of years * in 64 bits, so.. */ |
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x = div_u64(x * TICK_NSEC, (NSEC_PER_SEC / USER_HZ)); |
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#endif return x; } |
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EXPORT_SYMBOL(jiffies_64_to_clock_t); u64 nsec_to_clock_t(u64 x) { #if (NSEC_PER_SEC % USER_HZ) == 0 |
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return div_u64(x, NSEC_PER_SEC / USER_HZ); |
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#elif (USER_HZ % 512) == 0 |
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return div_u64(x * USER_HZ / 512, NSEC_PER_SEC / 512); |
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#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, ... */ |
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return div_u64(x * 9, (9ull * NSEC_PER_SEC + (USER_HZ / 2)) / USER_HZ); |
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#endif |
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} |
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/** * 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 } |
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#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; } |
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EXPORT_SYMBOL(get_jiffies_64); #endif EXPORT_SYMBOL(jiffies); |
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/* * 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; } |