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Alarm delivery could be noticably late in the !CONFIG_NOHZ case because lost ticks weren't being taken into account. This is now treated more carefully, with the time between ticks being calculated and the appropriate number of ticks delivered to the timekeeping system. Cc: Nix <nix@esperi.org.uk> Signed-off-by: Jeff Dike <jdike@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
181 lines
3.9 KiB
C
181 lines
3.9 KiB
C
/*
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* Copyright (C) 2000 - 2007 Jeff Dike (jdike{addtoit,linux.intel}.com)
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* Licensed under the GPL
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*/
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#include <stddef.h>
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#include <errno.h>
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#include <signal.h>
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#include <time.h>
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#include <sys/time.h>
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#include "kern_constants.h"
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#include "kern_util.h"
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#include "os.h"
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#include "process.h"
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#include "user.h"
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int set_interval(void)
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{
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int usec = UM_USEC_PER_SEC / UM_HZ;
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struct itimerval interval = ((struct itimerval) { { 0, usec },
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{ 0, usec } });
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if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
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return -errno;
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return 0;
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}
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int timer_one_shot(int ticks)
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{
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unsigned long usec = ticks * UM_USEC_PER_SEC / UM_HZ;
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unsigned long sec = usec / UM_USEC_PER_SEC;
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struct itimerval interval;
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usec %= UM_USEC_PER_SEC;
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interval = ((struct itimerval) { { 0, 0 }, { sec, usec } });
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if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
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return -errno;
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return 0;
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}
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/**
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* timeval_to_ns - Convert timeval to nanoseconds
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* @ts: pointer to the timeval variable to be converted
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*
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* Returns the scalar nanosecond representation of the timeval
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* parameter.
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*
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* Ripped from linux/time.h because it's a kernel header, and thus
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* unusable from here.
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*/
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static inline long long timeval_to_ns(const struct timeval *tv)
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{
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return ((long long) tv->tv_sec * UM_NSEC_PER_SEC) +
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tv->tv_usec * UM_NSEC_PER_USEC;
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}
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long long disable_timer(void)
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{
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struct itimerval time = ((struct itimerval) { { 0, 0 }, { 0, 0 } });
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int remain, max = UM_NSEC_PER_SEC / UM_HZ;
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if (setitimer(ITIMER_VIRTUAL, &time, &time) < 0)
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printk(UM_KERN_ERR "disable_timer - setitimer failed, "
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"errno = %d\n", errno);
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remain = timeval_to_ns(&time.it_value);
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if (remain > max)
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remain = max;
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return remain;
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}
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long long os_nsecs(void)
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{
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struct timeval tv;
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gettimeofday(&tv, NULL);
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return timeval_to_ns(&tv);
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}
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#ifdef UML_CONFIG_NO_HZ
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static int after_sleep_interval(struct timespec *ts)
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{
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return 0;
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}
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static void deliver_alarm(void)
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{
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alarm_handler(SIGVTALRM, NULL);
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}
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static unsigned long long sleep_time(unsigned long long nsecs)
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{
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return nsecs;
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}
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#else
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unsigned long long last_tick;
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unsigned long long skew;
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static void deliver_alarm(void)
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{
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unsigned long long this_tick = os_nsecs();
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int one_tick = UM_NSEC_PER_SEC / UM_HZ;
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if (last_tick == 0)
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last_tick = this_tick - one_tick;
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skew += this_tick - last_tick;
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while (skew >= one_tick) {
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alarm_handler(SIGVTALRM, NULL);
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skew -= one_tick;
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}
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last_tick = this_tick;
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}
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static unsigned long long sleep_time(unsigned long long nsecs)
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{
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return nsecs > skew ? nsecs - skew : 0;
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}
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static inline long long timespec_to_us(const struct timespec *ts)
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{
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return ((long long) ts->tv_sec * UM_USEC_PER_SEC) +
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ts->tv_nsec / UM_NSEC_PER_USEC;
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}
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static int after_sleep_interval(struct timespec *ts)
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{
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int usec = UM_USEC_PER_SEC / UM_HZ;
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long long start_usecs = timespec_to_us(ts);
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struct timeval tv;
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struct itimerval interval;
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/*
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* It seems that rounding can increase the value returned from
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* setitimer to larger than the one passed in. Over time,
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* this will cause the remaining time to be greater than the
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* tick interval. If this happens, then just reduce the first
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* tick to the interval value.
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*/
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if (start_usecs > usec)
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start_usecs = usec;
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start_usecs -= skew / UM_NSEC_PER_USEC;
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tv = ((struct timeval) { .tv_sec = start_usecs / UM_USEC_PER_SEC,
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.tv_usec = start_usecs % UM_USEC_PER_SEC });
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interval = ((struct itimerval) { { 0, usec }, tv });
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if (setitimer(ITIMER_VIRTUAL, &interval, NULL) == -1)
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return -errno;
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return 0;
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}
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#endif
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void idle_sleep(unsigned long long nsecs)
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{
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struct timespec ts;
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/*
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* nsecs can come in as zero, in which case, this starts a
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* busy loop. To prevent this, reset nsecs to the tick
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* interval if it is zero.
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*/
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if (nsecs == 0)
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nsecs = UM_NSEC_PER_SEC / UM_HZ;
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nsecs = sleep_time(nsecs);
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ts = ((struct timespec) { .tv_sec = nsecs / UM_NSEC_PER_SEC,
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.tv_nsec = nsecs % UM_NSEC_PER_SEC });
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if (nanosleep(&ts, &ts) == 0)
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deliver_alarm();
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after_sleep_interval(&ts);
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}
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