aboutsummaryrefslogtreecommitdiffstats
path: root/kernel/timer.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/timer.c')
-rw-r--r--kernel/timer.c459
1 files changed, 1 insertions, 458 deletions
diff --git a/kernel/timer.c b/kernel/timer.c
index dbe966feff2f..ba41af2bb6cc 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -1,7 +1,7 @@
1/* 1/*
2 * linux/kernel/timer.c 2 * linux/kernel/timer.c
3 * 3 *
4 * Kernel internal timers, kernel timekeeping, basic process system calls 4 * Kernel internal timers, basic process system calls
5 * 5 *
6 * Copyright (C) 1991, 1992 Linus Torvalds 6 * Copyright (C) 1991, 1992 Linus Torvalds
7 * 7 *
@@ -794,455 +794,6 @@ unsigned long next_timer_interrupt(void)
794 794
795#endif 795#endif
796 796
797/******************************************************************/
798
799/*
800 * The current time
801 * wall_to_monotonic is what we need to add to xtime (or xtime corrected
802 * for sub jiffie times) to get to monotonic time. Monotonic is pegged
803 * at zero at system boot time, so wall_to_monotonic will be negative,
804 * however, we will ALWAYS keep the tv_nsec part positive so we can use
805 * the usual normalization.
806 */
807struct timespec xtime __attribute__ ((aligned (16)));
808struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
809
810EXPORT_SYMBOL(xtime);
811
812
813/* XXX - all of this timekeeping code should be later moved to time.c */
814#include <linux/clocksource.h>
815static struct clocksource *clock; /* pointer to current clocksource */
816
817#ifdef CONFIG_GENERIC_TIME
818/**
819 * __get_nsec_offset - Returns nanoseconds since last call to periodic_hook
820 *
821 * private function, must hold xtime_lock lock when being
822 * called. Returns the number of nanoseconds since the
823 * last call to update_wall_time() (adjusted by NTP scaling)
824 */
825static inline s64 __get_nsec_offset(void)
826{
827 cycle_t cycle_now, cycle_delta;
828 s64 ns_offset;
829
830 /* read clocksource: */
831 cycle_now = clocksource_read(clock);
832
833 /* calculate the delta since the last update_wall_time: */
834 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
835
836 /* convert to nanoseconds: */
837 ns_offset = cyc2ns(clock, cycle_delta);
838
839 return ns_offset;
840}
841
842/**
843 * __get_realtime_clock_ts - Returns the time of day in a timespec
844 * @ts: pointer to the timespec to be set
845 *
846 * Returns the time of day in a timespec. Used by
847 * do_gettimeofday() and get_realtime_clock_ts().
848 */
849static inline void __get_realtime_clock_ts(struct timespec *ts)
850{
851 unsigned long seq;
852 s64 nsecs;
853
854 do {
855 seq = read_seqbegin(&xtime_lock);
856
857 *ts = xtime;
858 nsecs = __get_nsec_offset();
859
860 } while (read_seqretry(&xtime_lock, seq));
861
862 timespec_add_ns(ts, nsecs);
863}
864
865/**
866 * getnstimeofday - Returns the time of day in a timespec
867 * @ts: pointer to the timespec to be set
868 *
869 * Returns the time of day in a timespec.
870 */
871void getnstimeofday(struct timespec *ts)
872{
873 __get_realtime_clock_ts(ts);
874}
875
876EXPORT_SYMBOL(getnstimeofday);
877
878/**
879 * do_gettimeofday - Returns the time of day in a timeval
880 * @tv: pointer to the timeval to be set
881 *
882 * NOTE: Users should be converted to using get_realtime_clock_ts()
883 */
884void do_gettimeofday(struct timeval *tv)
885{
886 struct timespec now;
887
888 __get_realtime_clock_ts(&now);
889 tv->tv_sec = now.tv_sec;
890 tv->tv_usec = now.tv_nsec/1000;
891}
892
893EXPORT_SYMBOL(do_gettimeofday);
894/**
895 * do_settimeofday - Sets the time of day
896 * @tv: pointer to the timespec variable containing the new time
897 *
898 * Sets the time of day to the new time and update NTP and notify hrtimers
899 */
900int do_settimeofday(struct timespec *tv)
901{
902 unsigned long flags;
903 time_t wtm_sec, sec = tv->tv_sec;
904 long wtm_nsec, nsec = tv->tv_nsec;
905
906 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
907 return -EINVAL;
908
909 write_seqlock_irqsave(&xtime_lock, flags);
910
911 nsec -= __get_nsec_offset();
912
913 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
914 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
915
916 set_normalized_timespec(&xtime, sec, nsec);
917 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
918
919 clock->error = 0;
920 ntp_clear();
921
922 update_vsyscall(&xtime, clock);
923
924 write_sequnlock_irqrestore(&xtime_lock, flags);
925
926 /* signal hrtimers about time change */
927 clock_was_set();
928
929 return 0;
930}
931
932EXPORT_SYMBOL(do_settimeofday);
933
934/**
935 * change_clocksource - Swaps clocksources if a new one is available
936 *
937 * Accumulates current time interval and initializes new clocksource
938 */
939static void change_clocksource(void)
940{
941 struct clocksource *new;
942 cycle_t now;
943 u64 nsec;
944
945 new = clocksource_get_next();
946
947 if (clock == new)
948 return;
949
950 now = clocksource_read(new);
951 nsec = __get_nsec_offset();
952 timespec_add_ns(&xtime, nsec);
953
954 clock = new;
955 clock->cycle_last = now;
956
957 clock->error = 0;
958 clock->xtime_nsec = 0;
959 clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
960
961 tick_clock_notify();
962
963 printk(KERN_INFO "Time: %s clocksource has been installed.\n",
964 clock->name);
965}
966#else
967static inline void change_clocksource(void) { }
968#endif
969
970/**
971 * timekeeping_is_continuous - check to see if timekeeping is free running
972 */
973int timekeeping_is_continuous(void)
974{
975 unsigned long seq;
976 int ret;
977
978 do {
979 seq = read_seqbegin(&xtime_lock);
980
981 ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
982
983 } while (read_seqretry(&xtime_lock, seq));
984
985 return ret;
986}
987
988/**
989 * read_persistent_clock - Return time in seconds from the persistent clock.
990 *
991 * Weak dummy function for arches that do not yet support it.
992 * Returns seconds from epoch using the battery backed persistent clock.
993 * Returns zero if unsupported.
994 *
995 * XXX - Do be sure to remove it once all arches implement it.
996 */
997unsigned long __attribute__((weak)) read_persistent_clock(void)
998{
999 return 0;
1000}
1001
1002/*
1003 * timekeeping_init - Initializes the clocksource and common timekeeping values
1004 */
1005void __init timekeeping_init(void)
1006{
1007 unsigned long flags;
1008 unsigned long sec = read_persistent_clock();
1009
1010 write_seqlock_irqsave(&xtime_lock, flags);
1011
1012 ntp_clear();
1013
1014 clock = clocksource_get_next();
1015 clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
1016 clock->cycle_last = clocksource_read(clock);
1017
1018 xtime.tv_sec = sec;
1019 xtime.tv_nsec = 0;
1020 set_normalized_timespec(&wall_to_monotonic,
1021 -xtime.tv_sec, -xtime.tv_nsec);
1022
1023 write_sequnlock_irqrestore(&xtime_lock, flags);
1024}
1025
1026/* flag for if timekeeping is suspended */
1027static int timekeeping_suspended;
1028/* time in seconds when suspend began */
1029static unsigned long timekeeping_suspend_time;
1030
1031/**
1032 * timekeeping_resume - Resumes the generic timekeeping subsystem.
1033 * @dev: unused
1034 *
1035 * This is for the generic clocksource timekeeping.
1036 * xtime/wall_to_monotonic/jiffies/etc are
1037 * still managed by arch specific suspend/resume code.
1038 */
1039static int timekeeping_resume(struct sys_device *dev)
1040{
1041 unsigned long flags;
1042 unsigned long now = read_persistent_clock();
1043
1044 write_seqlock_irqsave(&xtime_lock, flags);
1045
1046 if (now && (now > timekeeping_suspend_time)) {
1047 unsigned long sleep_length = now - timekeeping_suspend_time;
1048
1049 xtime.tv_sec += sleep_length;
1050 wall_to_monotonic.tv_sec -= sleep_length;
1051 }
1052 /* re-base the last cycle value */
1053 clock->cycle_last = clocksource_read(clock);
1054 clock->error = 0;
1055 timekeeping_suspended = 0;
1056 write_sequnlock_irqrestore(&xtime_lock, flags);
1057
1058 touch_softlockup_watchdog();
1059
1060 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
1061
1062 /* Resume hrtimers */
1063 hres_timers_resume();
1064
1065 return 0;
1066}
1067
1068static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
1069{
1070 unsigned long flags;
1071
1072 write_seqlock_irqsave(&xtime_lock, flags);
1073 timekeeping_suspended = 1;
1074 timekeeping_suspend_time = read_persistent_clock();
1075 write_sequnlock_irqrestore(&xtime_lock, flags);
1076
1077 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
1078
1079 return 0;
1080}
1081
1082/* sysfs resume/suspend bits for timekeeping */
1083static struct sysdev_class timekeeping_sysclass = {
1084 .resume = timekeeping_resume,
1085 .suspend = timekeeping_suspend,
1086 set_kset_name("timekeeping"),
1087};
1088
1089static struct sys_device device_timer = {
1090 .id = 0,
1091 .cls = &timekeeping_sysclass,
1092};
1093
1094static int __init timekeeping_init_device(void)
1095{
1096 int error = sysdev_class_register(&timekeeping_sysclass);
1097 if (!error)
1098 error = sysdev_register(&device_timer);
1099 return error;
1100}
1101
1102device_initcall(timekeeping_init_device);
1103
1104/*
1105 * If the error is already larger, we look ahead even further
1106 * to compensate for late or lost adjustments.
1107 */
1108static __always_inline int clocksource_bigadjust(s64 error, s64 *interval,
1109 s64 *offset)
1110{
1111 s64 tick_error, i;
1112 u32 look_ahead, adj;
1113 s32 error2, mult;
1114
1115 /*
1116 * Use the current error value to determine how much to look ahead.
1117 * The larger the error the slower we adjust for it to avoid problems
1118 * with losing too many ticks, otherwise we would overadjust and
1119 * produce an even larger error. The smaller the adjustment the
1120 * faster we try to adjust for it, as lost ticks can do less harm
1121 * here. This is tuned so that an error of about 1 msec is adusted
1122 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
1123 */
1124 error2 = clock->error >> (TICK_LENGTH_SHIFT + 22 - 2 * SHIFT_HZ);
1125 error2 = abs(error2);
1126 for (look_ahead = 0; error2 > 0; look_ahead++)
1127 error2 >>= 2;
1128
1129 /*
1130 * Now calculate the error in (1 << look_ahead) ticks, but first
1131 * remove the single look ahead already included in the error.
1132 */
1133 tick_error = current_tick_length() >>
1134 (TICK_LENGTH_SHIFT - clock->shift + 1);
1135 tick_error -= clock->xtime_interval >> 1;
1136 error = ((error - tick_error) >> look_ahead) + tick_error;
1137
1138 /* Finally calculate the adjustment shift value. */
1139 i = *interval;
1140 mult = 1;
1141 if (error < 0) {
1142 error = -error;
1143 *interval = -*interval;
1144 *offset = -*offset;
1145 mult = -1;
1146 }
1147 for (adj = 0; error > i; adj++)
1148 error >>= 1;
1149
1150 *interval <<= adj;
1151 *offset <<= adj;
1152 return mult << adj;
1153}
1154
1155/*
1156 * Adjust the multiplier to reduce the error value,
1157 * this is optimized for the most common adjustments of -1,0,1,
1158 * for other values we can do a bit more work.
1159 */
1160static void clocksource_adjust(struct clocksource *clock, s64 offset)
1161{
1162 s64 error, interval = clock->cycle_interval;
1163 int adj;
1164
1165 error = clock->error >> (TICK_LENGTH_SHIFT - clock->shift - 1);
1166 if (error > interval) {
1167 error >>= 2;
1168 if (likely(error <= interval))
1169 adj = 1;
1170 else
1171 adj = clocksource_bigadjust(error, &interval, &offset);
1172 } else if (error < -interval) {
1173 error >>= 2;
1174 if (likely(error >= -interval)) {
1175 adj = -1;
1176 interval = -interval;
1177 offset = -offset;
1178 } else
1179 adj = clocksource_bigadjust(error, &interval, &offset);
1180 } else
1181 return;
1182
1183 clock->mult += adj;
1184 clock->xtime_interval += interval;
1185 clock->xtime_nsec -= offset;
1186 clock->error -= (interval - offset) <<
1187 (TICK_LENGTH_SHIFT - clock->shift);
1188}
1189
1190/**
1191 * update_wall_time - Uses the current clocksource to increment the wall time
1192 *
1193 * Called from the timer interrupt, must hold a write on xtime_lock.
1194 */
1195static void update_wall_time(void)
1196{
1197 cycle_t offset;
1198
1199 /* Make sure we're fully resumed: */
1200 if (unlikely(timekeeping_suspended))
1201 return;
1202
1203#ifdef CONFIG_GENERIC_TIME
1204 offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask;
1205#else
1206 offset = clock->cycle_interval;
1207#endif
1208 clock->xtime_nsec += (s64)xtime.tv_nsec << clock->shift;
1209
1210 /* normally this loop will run just once, however in the
1211 * case of lost or late ticks, it will accumulate correctly.
1212 */
1213 while (offset >= clock->cycle_interval) {
1214 /* accumulate one interval */
1215 clock->xtime_nsec += clock->xtime_interval;
1216 clock->cycle_last += clock->cycle_interval;
1217 offset -= clock->cycle_interval;
1218
1219 if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) {
1220 clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift;
1221 xtime.tv_sec++;
1222 second_overflow();
1223 }
1224
1225 /* interpolator bits */
1226 time_interpolator_update(clock->xtime_interval
1227 >> clock->shift);
1228
1229 /* accumulate error between NTP and clock interval */
1230 clock->error += current_tick_length();
1231 clock->error -= clock->xtime_interval << (TICK_LENGTH_SHIFT - clock->shift);
1232 }
1233
1234 /* correct the clock when NTP error is too big */
1235 clocksource_adjust(clock, offset);
1236
1237 /* store full nanoseconds into xtime */
1238 xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift;
1239 clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift;
1240
1241 /* check to see if there is a new clocksource to use */
1242 change_clocksource();
1243 update_vsyscall(&xtime, clock);
1244}
1245
1246/* 797/*
1247 * Called from the timer interrupt handler to charge one tick to the current 798 * Called from the timer interrupt handler to charge one tick to the current
1248 * process. user_tick is 1 if the tick is user time, 0 for system. 799 * process. user_tick is 1 if the tick is user time, 0 for system.
@@ -1306,14 +857,6 @@ static inline void calc_load(unsigned long ticks)
1306} 857}
1307 858
1308/* 859/*
1309 * This read-write spinlock protects us from races in SMP while
1310 * playing with xtime and avenrun.
1311 */
1312__attribute__((weak)) __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
1313
1314EXPORT_SYMBOL(xtime_lock);
1315
1316/*
1317 * This function runs timers and the timer-tq in bottom half context. 860 * This function runs timers and the timer-tq in bottom half context.
1318 */ 861 */
1319static void run_timer_softirq(struct softirq_action *h) 862static void run_timer_softirq(struct softirq_action *h)