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![Stanislaw Gruszka](/assets/img/avatar_default.png)
Measure ITIMER_PROF and ITIMER_VIRT timers interval error between real ticks and requested by user. Take it into account when scheduling next tick. This patch introduce possibility where time between two consecutive tics is smaller then requested interval, it preserve however dependency that n tick is generated not earlier than n*interval time - counting from the beginning of periodic signal generation. Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Thomas Gleixner <tglx@linutronix.de> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> LKML-Reference: <1248862529-6063-3-git-send-email-sgruszka@redhat.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
290 lines
7 KiB
C
290 lines
7 KiB
C
/*
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* linux/kernel/itimer.c
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*
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* Copyright (C) 1992 Darren Senn
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*/
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/* These are all the functions necessary to implement itimers */
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#include <linux/mm.h>
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#include <linux/interrupt.h>
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#include <linux/syscalls.h>
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#include <linux/time.h>
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#include <linux/posix-timers.h>
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#include <linux/hrtimer.h>
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#include <asm/uaccess.h>
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/**
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* itimer_get_remtime - get remaining time for the timer
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*
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* @timer: the timer to read
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*
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* Returns the delta between the expiry time and now, which can be
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* less than zero or 1usec for an pending expired timer
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*/
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static struct timeval itimer_get_remtime(struct hrtimer *timer)
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{
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ktime_t rem = hrtimer_get_remaining(timer);
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/*
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* Racy but safe: if the itimer expires after the above
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* hrtimer_get_remtime() call but before this condition
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* then we return 0 - which is correct.
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*/
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if (hrtimer_active(timer)) {
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if (rem.tv64 <= 0)
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rem.tv64 = NSEC_PER_USEC;
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} else
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rem.tv64 = 0;
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return ktime_to_timeval(rem);
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}
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static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
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struct itimerval *const value)
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{
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cputime_t cval, cinterval;
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struct cpu_itimer *it = &tsk->signal->it[clock_id];
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spin_lock_irq(&tsk->sighand->siglock);
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cval = it->expires;
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cinterval = it->incr;
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if (!cputime_eq(cval, cputime_zero)) {
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struct task_cputime cputime;
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cputime_t t;
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thread_group_cputimer(tsk, &cputime);
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if (clock_id == CPUCLOCK_PROF)
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t = cputime_add(cputime.utime, cputime.stime);
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else
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/* CPUCLOCK_VIRT */
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t = cputime.utime;
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if (cputime_le(cval, t))
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/* about to fire */
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cval = jiffies_to_cputime(1);
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else
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cval = cputime_sub(cval, t);
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}
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spin_unlock_irq(&tsk->sighand->siglock);
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cputime_to_timeval(cval, &value->it_value);
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cputime_to_timeval(cinterval, &value->it_interval);
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}
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int do_getitimer(int which, struct itimerval *value)
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{
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struct task_struct *tsk = current;
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switch (which) {
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case ITIMER_REAL:
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spin_lock_irq(&tsk->sighand->siglock);
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value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
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value->it_interval =
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ktime_to_timeval(tsk->signal->it_real_incr);
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spin_unlock_irq(&tsk->sighand->siglock);
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break;
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case ITIMER_VIRTUAL:
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get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
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break;
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case ITIMER_PROF:
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get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
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break;
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default:
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return(-EINVAL);
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}
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return 0;
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}
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SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
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{
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int error = -EFAULT;
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struct itimerval get_buffer;
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if (value) {
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error = do_getitimer(which, &get_buffer);
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if (!error &&
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copy_to_user(value, &get_buffer, sizeof(get_buffer)))
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error = -EFAULT;
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}
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return error;
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}
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/*
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* The timer is automagically restarted, when interval != 0
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*/
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enum hrtimer_restart it_real_fn(struct hrtimer *timer)
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{
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struct signal_struct *sig =
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container_of(timer, struct signal_struct, real_timer);
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kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
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return HRTIMER_NORESTART;
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}
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static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
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{
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struct timespec ts;
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s64 cpu_ns;
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cputime_to_timespec(ct, &ts);
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cpu_ns = timespec_to_ns(&ts);
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return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
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}
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static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
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const struct itimerval *const value,
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struct itimerval *const ovalue)
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{
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cputime_t cval, nval, cinterval, ninterval;
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s64 ns_ninterval, ns_nval;
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struct cpu_itimer *it = &tsk->signal->it[clock_id];
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nval = timeval_to_cputime(&value->it_value);
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ns_nval = timeval_to_ns(&value->it_value);
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ninterval = timeval_to_cputime(&value->it_interval);
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ns_ninterval = timeval_to_ns(&value->it_interval);
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it->incr_error = cputime_sub_ns(ninterval, ns_ninterval);
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it->error = cputime_sub_ns(nval, ns_nval);
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spin_lock_irq(&tsk->sighand->siglock);
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cval = it->expires;
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cinterval = it->incr;
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if (!cputime_eq(cval, cputime_zero) ||
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!cputime_eq(nval, cputime_zero)) {
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if (cputime_gt(nval, cputime_zero))
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nval = cputime_add(nval, jiffies_to_cputime(1));
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set_process_cpu_timer(tsk, clock_id, &nval, &cval);
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}
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it->expires = nval;
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it->incr = ninterval;
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spin_unlock_irq(&tsk->sighand->siglock);
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if (ovalue) {
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cputime_to_timeval(cval, &ovalue->it_value);
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cputime_to_timeval(cinterval, &ovalue->it_interval);
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}
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}
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/*
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* Returns true if the timeval is in canonical form
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*/
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#define timeval_valid(t) \
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(((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
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int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
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{
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struct task_struct *tsk = current;
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struct hrtimer *timer;
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ktime_t expires;
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/*
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* Validate the timevals in value.
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*/
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if (!timeval_valid(&value->it_value) ||
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!timeval_valid(&value->it_interval))
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return -EINVAL;
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switch (which) {
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case ITIMER_REAL:
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again:
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spin_lock_irq(&tsk->sighand->siglock);
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timer = &tsk->signal->real_timer;
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if (ovalue) {
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ovalue->it_value = itimer_get_remtime(timer);
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ovalue->it_interval
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= ktime_to_timeval(tsk->signal->it_real_incr);
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}
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/* We are sharing ->siglock with it_real_fn() */
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if (hrtimer_try_to_cancel(timer) < 0) {
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spin_unlock_irq(&tsk->sighand->siglock);
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goto again;
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}
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expires = timeval_to_ktime(value->it_value);
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if (expires.tv64 != 0) {
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tsk->signal->it_real_incr =
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timeval_to_ktime(value->it_interval);
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hrtimer_start(timer, expires, HRTIMER_MODE_REL);
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} else
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tsk->signal->it_real_incr.tv64 = 0;
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spin_unlock_irq(&tsk->sighand->siglock);
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break;
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case ITIMER_VIRTUAL:
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set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
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break;
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case ITIMER_PROF:
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set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
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break;
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default:
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return -EINVAL;
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}
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return 0;
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}
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/**
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* alarm_setitimer - set alarm in seconds
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*
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* @seconds: number of seconds until alarm
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* 0 disables the alarm
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*
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* Returns the remaining time in seconds of a pending timer or 0 when
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* the timer is not active.
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*
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* On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
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* negative timeval settings which would cause immediate expiry.
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*/
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unsigned int alarm_setitimer(unsigned int seconds)
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{
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struct itimerval it_new, it_old;
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#if BITS_PER_LONG < 64
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if (seconds > INT_MAX)
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seconds = INT_MAX;
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#endif
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it_new.it_value.tv_sec = seconds;
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it_new.it_value.tv_usec = 0;
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it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
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do_setitimer(ITIMER_REAL, &it_new, &it_old);
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/*
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* We can't return 0 if we have an alarm pending ... And we'd
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* better return too much than too little anyway
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*/
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if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
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it_old.it_value.tv_usec >= 500000)
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it_old.it_value.tv_sec++;
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return it_old.it_value.tv_sec;
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}
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SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
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struct itimerval __user *, ovalue)
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{
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struct itimerval set_buffer, get_buffer;
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int error;
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if (value) {
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if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
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return -EFAULT;
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} else
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memset((char *) &set_buffer, 0, sizeof(set_buffer));
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error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
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if (error || !ovalue)
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return error;
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if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
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return -EFAULT;
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return 0;
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}
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