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/smp_lock.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/syscalls.h>
  13 #include <linux/time.h>
  14 #include <linux/posix-timers.h>
  15 #include <linux/hrtimer.h>
  16
  17 #include <asm/uaccess.h>
  18
  19 /**
  20  * itimer_get_remtime - get remaining time for the timer
  21  *
  22  * @timer: the timer to read
  23  *
  24  * Returns the delta between the expiry time and now, which can be
  25  * less than zero or 1usec for an pending expired timer
  26  */
  27 static struct timeval itimer_get_remtime(struct hrtimer *timer)
  28 {
  29         ktime_t rem = hrtimer_get_remaining(timer);
  30
  31         /*
  32          * Racy but safe: if the itimer expires after the above
  33          * hrtimer_get_remtime() call but before this condition
  34          * then we return 0 - which is correct.
  35          */
  36         if (hrtimer_active(timer)) {
  37                 if (rem.tv64 <= 0)
  38                         rem.tv64 = NSEC_PER_USEC;
  39         } else
  40                 rem.tv64 = 0;
  41
  42         return ktime_to_timeval(rem);
  43 }
  44
  45 int do_getitimer(int which, struct itimerval *value)
  46 {
  47         struct task_struct *tsk = current;
  48         cputime_t cinterval, cval;
  49
  50         switch (which) {
  51         case ITIMER_REAL:
  52                 spin_lock_irq(&tsk->sighand->siglock);
  53                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
  54                 value->it_interval =
  55                         ktime_to_timeval(tsk->signal->it_real_incr);
  56                 spin_unlock_irq(&tsk->sighand->siglock);
  57                 break;
  58         case ITIMER_VIRTUAL:
  59                 read_lock(&tasklist_lock);
  60                 spin_lock_irq(&tsk->sighand->siglock);
  61                 cval = tsk->signal->it_virt_expires;
  62                 cinterval = tsk->signal->it_virt_incr;
  63                 if (!cputime_eq(cval, cputime_zero)) {
  64                         struct task_struct *t = tsk;
  65                         cputime_t utime = tsk->signal->utime;
  66                         do {
  67                                 utime = cputime_add(utime, t->utime);
  68                                 t = next_thread(t);
  69                         } while (t != tsk);
  70                         if (cputime_le(cval, utime)) { /* about to fire */
  71                                 cval = jiffies_to_cputime(1);
  72                         } else {
  73                                 cval = cputime_sub(cval, utime);
  74                         }
  75                 }
  76                 spin_unlock_irq(&tsk->sighand->siglock);
  77                 read_unlock(&tasklist_lock);
  78                 cputime_to_timeval(cval, &value->it_value);
  79                 cputime_to_timeval(cinterval, &value->it_interval);
  80                 break;
  81         case ITIMER_PROF:
  82                 read_lock(&tasklist_lock);
  83                 spin_lock_irq(&tsk->sighand->siglock);
  84                 cval = tsk->signal->it_prof_expires;
  85                 cinterval = tsk->signal->it_prof_incr;
  86                 if (!cputime_eq(cval, cputime_zero)) {
  87                         struct task_struct *t = tsk;
  88                         cputime_t ptime = cputime_add(tsk->signal->utime,
  89                                                       tsk->signal->stime);
  90                         do {
  91                                 ptime = cputime_add(ptime,
  92                                                     cputime_add(t->utime,
  93                                                                 t->stime));
  94                                 t = next_thread(t);
  95                         } while (t != tsk);
  96                         if (cputime_le(cval, ptime)) { /* about to fire */
  97                                 cval = jiffies_to_cputime(1);
  98                         } else {
  99                                 cval = cputime_sub(cval, ptime);
 100                         }
 101                 }
 102                 spin_unlock_irq(&tsk->sighand->siglock);
 103                 read_unlock(&tasklist_lock);
 104                 cputime_to_timeval(cval, &value->it_value);
 105                 cputime_to_timeval(cinterval, &value->it_interval);
 106                 break;
 107         default:
 108                 return(-EINVAL);
 109         }
 110         return 0;
 111 }
 112
 113 asmlinkage long sys_getitimer(int which, struct itimerval __user *value)
 114 {
 115         int error = -EFAULT;
 116         struct itimerval get_buffer;
 117
 118         if (value) {
 119                 error = do_getitimer(which, &get_buffer);
 120                 if (!error &&
 121                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
 122                         error = -EFAULT;
 123         }
 124         return error;
 125 }
 126
 127
 128 /*
 129  * The timer is automagically restarted, when interval != 0
 130  */
 131 int it_real_fn(void *data)
 132 {
 133         struct task_struct *tsk = (struct task_struct *) data;
 134
 135         send_group_sig_info(SIGALRM, SEND_SIG_PRIV, tsk);
 136
 137         if (tsk->signal->it_real_incr.tv64 != 0) {
 138                 hrtimer_forward(&tsk->signal->real_timer,
 139                                tsk->signal->it_real_incr);
 140
 141                 return HRTIMER_RESTART;
 142         }
 143         return HRTIMER_NORESTART;
 144 }
 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         switch (which) {
 154         case ITIMER_REAL:
 155 again:
 156                 spin_lock_irq(&tsk->sighand->siglock);
 157                 timer = &tsk->signal->real_timer;
 158                 if (ovalue) {
 159                         ovalue->it_value = itimer_get_remtime(timer);
 160                         ovalue->it_interval
 161                                 = ktime_to_timeval(tsk->signal->it_real_incr);
 162                 }
 163                 /* We are sharing ->siglock with it_real_fn() */
 164                 if (hrtimer_try_to_cancel(timer) < 0) {
 165                         spin_unlock_irq(&tsk->sighand->siglock);
 166                         goto again;
 167                 }
 168                 tsk->signal->it_real_incr =
 169                         timeval_to_ktime(value->it_interval);
 170                 expires = timeval_to_ktime(value->it_value);
 171                 if (expires.tv64 != 0)
 172                         hrtimer_start(timer, expires, HRTIMER_REL);
 173                 spin_unlock_irq(&tsk->sighand->siglock);
 174                 break;
 175         case ITIMER_VIRTUAL:
 176                 nval = timeval_to_cputime(&value->it_value);
 177                 ninterval = timeval_to_cputime(&value->it_interval);
 178                 read_lock(&tasklist_lock);
 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                 read_unlock(&tasklist_lock);
 194                 if (ovalue) {
 195                         cputime_to_timeval(cval, &ovalue->it_value);
 196                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 197                 }
 198                 break;
 199         case ITIMER_PROF:
 200                 nval = timeval_to_cputime(&value->it_value);
 201                 ninterval = timeval_to_cputime(&value->it_interval);
 202                 read_lock(&tasklist_lock);
 203                 spin_lock_irq(&tsk->sighand->siglock);
 204                 cval = tsk->signal->it_prof_expires;
 205                 cinterval = tsk->signal->it_prof_incr;
 206                 if (!cputime_eq(cval, cputime_zero) ||
 207                     !cputime_eq(nval, cputime_zero)) {
 208                         if (cputime_gt(nval, cputime_zero))
 209                                 nval = cputime_add(nval,
 210                                                    jiffies_to_cputime(1));
 211                         set_process_cpu_timer(tsk, CPUCLOCK_PROF,
 212                                               &nval, &cval);
 213                 }
 214                 tsk->signal->it_prof_expires = nval;
 215                 tsk->signal->it_prof_incr = ninterval;
 216                 spin_unlock_irq(&tsk->sighand->siglock);
 217                 read_unlock(&tasklist_lock);
 218                 if (ovalue) {
 219                         cputime_to_timeval(cval, &ovalue->it_value);
 220                         cputime_to_timeval(cinterval, &ovalue->it_interval);
 221                 }
 222                 break;
 223         default:
 224                 return -EINVAL;
 225         }
 226         return 0;
 227 }
 228
 229 asmlinkage long sys_setitimer(int which,
 230                               struct itimerval __user *value,
 231                               struct itimerval __user *ovalue)
 232 {
 233         struct itimerval set_buffer, get_buffer;
 234         int error;
 235
 236         if (value) {
 237                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
 238                         return -EFAULT;
 239         } else
 240                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
 241
 242         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
 243         if (error || !ovalue)
 244                 return error;
 245
 246         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
 247                 return -EFAULT;
 248         return 0;
 249 }