linux/kernel/itimer.c
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   1/*
   2 * linux/kernel/itimer.c
   3 *
   4 * Copyright (C) 1992 Darren Senn
   5 */
   6
   7/* These are all the functions necessary to implement itimers */
   8
   9#include <linux/mm.h>
  10#include <linux/interrupt.h>
  11#include <linux/syscalls.h>
  12#include <linux/time.h>
  13#include <linux/posix-timers.h>
  14#include <linux/hrtimer.h>
  15
  16#include <asm/uaccess.h>
  17
  18/**
  19 * itimer_get_remtime - get remaining time for the timer
  20 *
  21 * @timer: the timer to read
  22 *
  23 * Returns the delta between the expiry time and now, which can be
  24 * less than zero or 1usec for an pending expired timer
  25 */
  26static struct timeval itimer_get_remtime(struct hrtimer *timer)
  27{
  28        ktime_t rem = hrtimer_get_remaining(timer);
  29
  30        /*
  31         * Racy but safe: if the itimer expires after the above
  32         * hrtimer_get_remtime() call but before this condition
  33         * then we return 0 - which is correct.
  34         */
  35        if (hrtimer_active(timer)) {
  36                if (rem.tv64 <= 0)
  37                        rem.tv64 = NSEC_PER_USEC;
  38        } else
  39                rem.tv64 = 0;
  40
  41        return ktime_to_timeval(rem);
  42}
  43
  44int do_getitimer(int which, struct itimerval *value)
  45{
  46        struct task_struct *tsk = current;
  47        cputime_t cinterval, cval;
  48
  49        switch (which) {
  50        case ITIMER_REAL:
  51                spin_lock_irq(&tsk->sighand->siglock);
  52                value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  53                value->it_interval =
  54                        ktime_to_timeval(tsk->signal->it_real_incr);
  55                spin_unlock_irq(&tsk->sighand->siglock);
  56                break;
  57        case ITIMER_VIRTUAL:
  58                spin_lock_irq(&tsk->sighand->siglock);
  59                cval = tsk->signal->it_virt_expires;
  60                cinterval = tsk->signal->it_virt_incr;
  61                if (!cputime_eq(cval, cputime_zero)) {
  62                        struct task_cputime cputime;
  63                        cputime_t utime;
  64
  65                        thread_group_cputime(tsk, &cputime);
  66                        utime = cputime.utime;
  67                        if (cputime_le(cval, utime)) { /* about to fire */
  68                                cval = jiffies_to_cputime(1);
  69                        } else {
  70                                cval = cputime_sub(cval, utime);
  71                        }
  72                }
  73                spin_unlock_irq(&tsk->sighand->siglock);
  74                cputime_to_timeval(cval, &value->it_value);
  75                cputime_to_timeval(cinterval, &value->it_interval);
  76                break;
  77        case ITIMER_PROF:
  78                spin_lock_irq(&tsk->sighand->siglock);
  79                cval = tsk->signal->it_prof_expires;
  80                cinterval = tsk->signal->it_prof_incr;
  81                if (!cputime_eq(cval, cputime_zero)) {
  82                        struct task_cputime times;
  83                        cputime_t ptime;
  84
  85                        thread_group_cputime(tsk, &times);
  86                        ptime = cputime_add(times.utime, times.stime);
  87                        if (cputime_le(cval, ptime)) { /* about to fire */
  88                                cval = jiffies_to_cputime(1);
  89                        } else {
  90                                cval = cputime_sub(cval, ptime);
  91                        }
  92                }
  93                spin_unlock_irq(&tsk->sighand->siglock);
  94                cputime_to_timeval(cval, &value->it_value);
  95                cputime_to_timeval(cinterval, &value->it_interval);
  96                break;
  97        default:
  98                return(-EINVAL);
  99        }
 100        return 0;
 101}
 102
 103SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
 104{
 105        int error = -EFAULT;
 106        struct itimerval get_buffer;
 107
 108        if (value) {
 109                error = do_getitimer(which, &get_buffer);
 110                if (!error &&
 111                    copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 112                        error = -EFAULT;
 113        }
 114        return error;
 115}
 116
 117
 118/*
 119 * The timer is automagically restarted, when interval != 0
 120 */
 121enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 122{
 123        struct signal_struct *sig =
 124                container_of(timer, struct signal_struct, real_timer);
 125
 126        kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 127
 128        return HRTIMER_NORESTART;
 129}
 130
 131/*
 132 * Returns true if the timeval is in canonical form
 133 */
 134#define timeval_valid(t) \
 135        (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 136
 137int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 138{
 139        struct task_struct *tsk = current;
 140        struct hrtimer *timer;
 141        ktime_t expires;
 142        cputime_t cval, cinterval, nval, ninterval;
 143
 144        /*
 145         * Validate the timevals in value.
 146         */
 147        if (!timeval_valid(&value->it_value) ||
 148            !timeval_valid(&value->it_interval))
 149                return -EINVAL;
 150
 151        switch (which) {
 152        case ITIMER_REAL:
 153again:
 154                spin_lock_irq(&tsk->sighand->siglock);
 155                timer = &tsk->signal->real_timer;
 156                if (ovalue) {
 157                        ovalue->it_value = itimer_get_remtime(timer);
 158                        ovalue->it_interval
 159                                = ktime_to_timeval(tsk->signal->it_real_incr);
 160                }
 161                /* We are sharing ->siglock with it_real_fn() */
 162                if (hrtimer_try_to_cancel(timer) < 0) {
 163                        spin_unlock_irq(&tsk->sighand->siglock);
 164                        goto again;
 165                }
 166                expires = timeval_to_ktime(value->it_value);
 167                if (expires.tv64 != 0) {
 168                        tsk->signal->it_real_incr =
 169                                timeval_to_ktime(value->it_interval);
 170                        hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 171                } else
 172                        tsk->signal->it_real_incr.tv64 = 0;
 173
 174                spin_unlock_irq(&tsk->sighand->siglock);
 175                break;
 176        case ITIMER_VIRTUAL:
 177                nval = timeval_to_cputime(&value->it_value);
 178                ninterval = timeval_to_cputime(&value->it_interval);
 179                spin_lock_irq(&tsk->sighand->siglock);
 180                cval = tsk->signal->it_virt_expires;
 181                cinterval = tsk->signal->it_virt_incr;
 182                if (!cputime_eq(cval, cputime_zero) ||
 183                    !cputime_eq(nval, cputime_zero)) {
 184                        if (cputime_gt(nval, cputime_zero))
 185                                nval = cputime_add(nval,
 186                                                   jiffies_to_cputime(1));
 187                        set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
 188                                              &nval, &cval);
 189                }
 190                tsk->signal->it_virt_expires = nval;
 191                tsk->signal->it_virt_incr = ninterval;
 192                spin_unlock_irq(&tsk->sighand->siglock);
 193                if (ovalue) {
 194                        cputime_to_timeval(cval, &ovalue->it_value);
 195                        cputime_to_timeval(cinterval, &ovalue->it_interval);
 196                }
 197                break;
 198        case ITIMER_PROF:
 199                nval = timeval_to_cputime(&value->it_value);
 200                ninterval = timeval_to_cputime(&value->it_interval);
 201                spin_lock_irq(&tsk->sighand->siglock);
 202                cval = tsk->signal->it_prof_expires;
 203                cinterval = tsk->signal->it_prof_incr;
 204                if (!cputime_eq(cval, cputime_zero) ||
 205                    !cputime_eq(nval, cputime_zero)) {
 206                        if (cputime_gt(nval, cputime_zero))
 207                                nval = cputime_add(nval,
 208                                                   jiffies_to_cputime(1));
 209                        set_process_cpu_timer(tsk, CPUCLOCK_PROF,
 210                                              &nval, &cval);
 211                }
 212                tsk->signal->it_prof_expires = nval;
 213                tsk->signal->it_prof_incr = ninterval;
 214                spin_unlock_irq(&tsk->sighand->siglock);
 215                if (ovalue) {
 216                        cputime_to_timeval(cval, &ovalue->it_value);
 217                        cputime_to_timeval(cinterval, &ovalue->it_interval);
 218                }
 219                break;
 220        default:
 221                return -EINVAL;
 222        }
 223        return 0;
 224}
 225
 226/**
 227 * alarm_setitimer - set alarm in seconds
 228 *
 229 * @seconds:    number of seconds until alarm
 230 *              0 disables the alarm
 231 *
 232 * Returns the remaining time in seconds of a pending timer or 0 when
 233 * the timer is not active.
 234 *
 235 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 236 * negative timeval settings which would cause immediate expiry.
 237 */
 238unsigned int alarm_setitimer(unsigned int seconds)
 239{
 240        struct itimerval it_new, it_old;
 241
 242#if BITS_PER_LONG < 64
 243        if (seconds > INT_MAX)
 244                seconds = INT_MAX;
 245#endif
 246        it_new.it_value.tv_sec = seconds;
 247        it_new.it_value.tv_usec = 0;
 248        it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 249
 250        do_setitimer(ITIMER_REAL, &it_new, &it_old);
 251
 252        /*
 253         * We can't return 0 if we have an alarm pending ...  And we'd
 254         * better return too much than too little anyway
 255         */
 256        if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 257              it_old.it_value.tv_usec >= 500000)
 258                it_old.it_value.tv_sec++;
 259
 260        return it_old.it_value.tv_sec;
 261}
 262
 263SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
 264                struct itimerval __user *, ovalue)
 265{
 266        struct itimerval set_buffer, get_buffer;
 267        int error;
 268
 269        if (value) {
 270                if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 271                        return -EFAULT;
 272        } else
 273                memset((char *) &set_buffer, 0, sizeof(set_buffer));
 274
 275        error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 276        if (error || !ovalue)
 277                return error;
 278
 279        if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 280                return -EFAULT;
 281        return 0;
 282}
 283
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