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  */
  26 static 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
  44 int 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
 112 asmlinkage 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  */
 130 enum 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         send_group_sig_info(SIGALRM, SEND_SIG_PRIV, sig->tsk);
 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
 146 int 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:
 162 again:
 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  */
 251 unsigned 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
 276 asmlinkage 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 }