LXR linux/kernel/itimer.c

   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                read_lock(&tasklist_lock);
  59                spin_lock_irq(&tsk->sighand->siglock);
  60                cval = tsk->signal->it_virt_expires;
  61                cinterval = tsk->signal->it_virt_incr;
  62                if (!cputime_eq(cval, cputime_zero)) {
  63                        struct task_struct *t = tsk;
  64                        cputime_t utime = tsk->signal->utime;
  65                        do {
  66                                utime = cputime_add(utime, t->utime);
  67                                t = next_thread(t);
  68                        } while (t != tsk);
  69                        if (cputime_le(cval, utime)) { /* about to fire */
  70                                cval = jiffies_to_cputime(1);
  71                        } else {
  72                                cval = cputime_sub(cval, utime);
  73                        }
  74                }
  75                spin_unlock_irq(&tsk->sighand->siglock);
  76                read_unlock(&tasklist_lock);
  77                cputime_to_timeval(cval, &value->it_value);
  78                cputime_to_timeval(cinterval, &value->it_interval);
  79                break;
  80        case ITIMER_PROF:
  81                read_lock(&tasklist_lock);
  82                spin_lock_irq(&tsk->sighand->siglock);
  83                cval = tsk->signal->it_prof_expires;
  84                cinterval = tsk->signal->it_prof_incr;
  85                if (!cputime_eq(cval, cputime_zero)) {
  86                        struct task_struct *t = tsk;
  87                        cputime_t ptime = cputime_add(tsk->signal->utime,
  88                                                      tsk->signal->stime);
  89                        do {
  90                                ptime = cputime_add(ptime,
  91                                                    cputime_add(t->utime,
  92                                                                t->stime));
  93                                t = next_thread(t);
  94                        } while (t != tsk);
  95                        if (cputime_le(cval, ptime)) { /* about to fire */
  96                                cval = jiffies_to_cputime(1);
  97                        } else {
  98                                cval = cputime_sub(cval, ptime);
  99                        }
 100                }
 101                spin_unlock_irq(&tsk->sighand->siglock);
 102                read_unlock(&tasklist_lock);
 103                cputime_to_timeval(cval, &value->it_value);
 104                cputime_to_timeval(cinterval, &value->it_interval);
 105                break;
 106        default:
 107                return(-EINVAL);
 108        }
 109        return 0;
 110}
 111
 112asmlinkage long sys_getitimer(int which, struct itimerval __user *value)
 113{
 114        int error = -EFAULT;
 115        struct itimerval get_buffer;
 116
 117        if (value) {
 118                error = do_getitimer(which, &get_buffer);
 119                if (!error &&
 120                    copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 121                        error = -EFAULT;
 122        }
 123        return error;
 124}
 125
 126
 127/*
 128 * The timer is automagically restarted, when interval != 0
 129 */
 130enum hrtimer_restart it_real_fn(struct hrtimer *timer)
 131{
 132        struct signal_struct *sig =
 133                container_of(timer, struct signal_struct, real_timer);
 134
 135        kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
 136
 137        return HRTIMER_NORESTART;
 138}
 139
 140/*
 141 * Returns true if the timeval is in canonical form
 142 */
 143#define timeval_valid(t) \
 144        (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
 145
 146int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
 147{
 148        struct task_struct *tsk = current;
 149        struct hrtimer *timer;
 150        ktime_t expires;
 151        cputime_t cval, cinterval, nval, ninterval;
 152
 153        /*
 154         * Validate the timevals in value.
 155         */
 156        if (!timeval_valid(&value->it_value) ||
 157            !timeval_valid(&value->it_interval))
 158                return -EINVAL;
 159
 160        switch (which) {
 161        case ITIMER_REAL:
 162again:
 163                spin_lock_irq(&tsk->sighand->siglock);
 164                timer = &tsk->signal->real_timer;
 165                if (ovalue) {
 166                        ovalue->it_value = itimer_get_remtime(timer);
 167                        ovalue->it_interval
 168                                = ktime_to_timeval(tsk->signal->it_real_incr);
 169                }
 170                /* We are sharing ->siglock with it_real_fn() */
 171                if (hrtimer_try_to_cancel(timer) < 0) {
 172                        spin_unlock_irq(&tsk->sighand->siglock);
 173                        goto again;
 174                }
 175                expires = timeval_to_ktime(value->it_value);
 176                if (expires.tv64 != 0) {
 177                        tsk->signal->it_real_incr =
 178                                timeval_to_ktime(value->it_interval);
 179                        hrtimer_start(timer, expires, HRTIMER_MODE_REL);
 180                } else
 181                        tsk->signal->it_real_incr.tv64 = 0;
 182
 183                spin_unlock_irq(&tsk->sighand->siglock);
 184                break;
 185        case ITIMER_VIRTUAL:
 186                nval = timeval_to_cputime(&value->it_value);
 187                ninterval = timeval_to_cputime(&value->it_interval);
 188                read_lock(&tasklist_lock);
 189                spin_lock_irq(&tsk->sighand->siglock);
 190                cval = tsk->signal->it_virt_expires;
 191                cinterval = tsk->signal->it_virt_incr;
 192                if (!cputime_eq(cval, cputime_zero) ||
 193                    !cputime_eq(nval, cputime_zero)) {
 194                        if (cputime_gt(nval, cputime_zero))
 195                                nval = cputime_add(nval,
 196                                                   jiffies_to_cputime(1));
 197                        set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
 198                                              &nval, &cval);
 199                }
 200                tsk->signal->it_virt_expires = nval;
 201                tsk->signal->it_virt_incr = ninterval;
 202                spin_unlock_irq(&tsk->sighand->siglock);
 203                read_unlock(&tasklist_lock);
 204                if (ovalue) {
 205                        cputime_to_timeval(cval, &ovalue->it_value);
 206                        cputime_to_timeval(cinterval, &ovalue->it_interval);
 207                }
 208                break;
 209        case ITIMER_PROF:
 210                nval = timeval_to_cputime(&value->it_value);
 211                ninterval = timeval_to_cputime(&value->it_interval);
 212                read_lock(&tasklist_lock);
 213                spin_lock_irq(&tsk->sighand->siglock);
 214                cval = tsk->signal->it_prof_expires;
 215                cinterval = tsk->signal->it_prof_incr;
 216                if (!cputime_eq(cval, cputime_zero) ||
 217                    !cputime_eq(nval, cputime_zero)) {
 218                        if (cputime_gt(nval, cputime_zero))
 219                                nval = cputime_add(nval,
 220                                                   jiffies_to_cputime(1));
 221                        set_process_cpu_timer(tsk, CPUCLOCK_PROF,
 222                                              &nval, &cval);
 223                }
 224                tsk->signal->it_prof_expires = nval;
 225                tsk->signal->it_prof_incr = ninterval;
 226                spin_unlock_irq(&tsk->sighand->siglock);
 227                read_unlock(&tasklist_lock);
 228                if (ovalue) {
 229                        cputime_to_timeval(cval, &ovalue->it_value);
 230                        cputime_to_timeval(cinterval, &ovalue->it_interval);
 231                }
 232                break;
 233        default:
 234                return -EINVAL;
 235        }
 236        return 0;
 237}
 238
 239/**
 240 * alarm_setitimer - set alarm in seconds
 241 *
 242 * @seconds:    number of seconds until alarm
 243 *              0 disables the alarm
 244 *
 245 * Returns the remaining time in seconds of a pending timer or 0 when
 246 * the timer is not active.
 247 *
 248 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
 249 * negative timeval settings which would cause immediate expiry.
 250 */
 251unsigned int alarm_setitimer(unsigned int seconds)
 252{
 253        struct itimerval it_new, it_old;
 254
 255#if BITS_PER_LONG < 64
 256        if (seconds > INT_MAX)
 257                seconds = INT_MAX;
 258#endif
 259        it_new.it_value.tv_sec = seconds;
 260        it_new.it_value.tv_usec = 0;
 261        it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
 262
 263        do_setitimer(ITIMER_REAL, &it_new, &it_old);
 264
 265        /*
 266         * We can't return 0 if we have an alarm pending ...  And we'd
 267         * better return too much than too little anyway
 268         */
 269        if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
 270              it_old.it_value.tv_usec >= 500000)
 271                it_old.it_value.tv_sec++;
 272
 273        return it_old.it_value.tv_sec;
 274}
 275
 276asmlinkage long sys_setitimer(int which,
 277                              struct itimerval __user *value,
 278                              struct itimerval __user *ovalue)
 279{
 280        struct itimerval set_buffer, get_buffer;
 281        int error;
 282
 283        if (value) {
 284                if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 285                        return -EFAULT;
 286        } else
 287                memset((char *) &set_buffer, 0, sizeof(set_buffer));
 288
 289        error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 290        if (error || !ovalue)
 291                return error;
 292
 293        if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 294                return -EFAULT;
 295        return 0;
 296}
 297