[PATCH] hrtimers: add high resolution timer support
[linux-3.10.git] / 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 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
132 {
133         struct signal_struct *sig =
134             container_of(timer, struct signal_struct, real_timer);
135
136         send_group_sig_info(SIGALRM, SEND_SIG_PRIV, sig->tsk);
137
138         if (sig->it_real_incr.tv64 != 0) {
139                 hrtimer_forward(timer, hrtimer_cb_get_time(timer),
140                                 sig->it_real_incr);
141                 return HRTIMER_RESTART;
142         }
143         return HRTIMER_NORESTART;
144 }
145
146 /*
147  * We do not care about correctness. We just sanitize the values so
148  * the ktime_t operations which expect normalized values do not
149  * break. This converts negative values to long timeouts similar to
150  * the code in kernel versions < 2.6.16
151  *
152  * Print a limited number of warning messages when an invalid timeval
153  * is detected.
154  */
155 static void fixup_timeval(struct timeval *tv, int interval)
156 {
157         static int warnlimit = 10;
158         unsigned long tmp;
159
160         if (warnlimit > 0) {
161                 warnlimit--;
162                 printk(KERN_WARNING
163                        "setitimer: %s (pid = %d) provided "
164                        "invalid timeval %s: tv_sec = %ld tv_usec = %ld\n",
165                        current->comm, current->pid,
166                        interval ? "it_interval" : "it_value",
167                        tv->tv_sec, (long) tv->tv_usec);
168         }
169
170         tmp = tv->tv_usec;
171         if (tmp >= USEC_PER_SEC) {
172                 tv->tv_usec = tmp % USEC_PER_SEC;
173                 tv->tv_sec += tmp / USEC_PER_SEC;
174         }
175
176         tmp = tv->tv_sec;
177         if (tmp > LONG_MAX)
178                 tv->tv_sec = LONG_MAX;
179 }
180
181 /*
182  * Returns true if the timeval is in canonical form
183  */
184 #define timeval_valid(t) \
185         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
186
187 /*
188  * Check for invalid timevals, sanitize them and print a limited
189  * number of warnings.
190  */
191 static void check_itimerval(struct itimerval *value) {
192
193         if (unlikely(!timeval_valid(&value->it_value)))
194                 fixup_timeval(&value->it_value, 0);
195
196         if (unlikely(!timeval_valid(&value->it_interval)))
197                 fixup_timeval(&value->it_interval, 1);
198 }
199
200 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
201 {
202         struct task_struct *tsk = current;
203         struct hrtimer *timer;
204         ktime_t expires;
205         cputime_t cval, cinterval, nval, ninterval;
206
207         /*
208          * Validate the timevals in value.
209          *
210          * Note: Although the spec requires that invalid values shall
211          * return -EINVAL, we just fixup the value and print a limited
212          * number of warnings in order not to break users of this
213          * historical misfeature.
214          *
215          * Scheduled for replacement in March 2007
216          */
217         check_itimerval(value);
218
219         switch (which) {
220         case ITIMER_REAL:
221 again:
222                 spin_lock_irq(&tsk->sighand->siglock);
223                 timer = &tsk->signal->real_timer;
224                 if (ovalue) {
225                         ovalue->it_value = itimer_get_remtime(timer);
226                         ovalue->it_interval
227                                 = ktime_to_timeval(tsk->signal->it_real_incr);
228                 }
229                 /* We are sharing ->siglock with it_real_fn() */
230                 if (hrtimer_try_to_cancel(timer) < 0) {
231                         spin_unlock_irq(&tsk->sighand->siglock);
232                         goto again;
233                 }
234                 tsk->signal->it_real_incr =
235                         timeval_to_ktime(value->it_interval);
236                 expires = timeval_to_ktime(value->it_value);
237                 if (expires.tv64 != 0)
238                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
239                 spin_unlock_irq(&tsk->sighand->siglock);
240                 break;
241         case ITIMER_VIRTUAL:
242                 nval = timeval_to_cputime(&value->it_value);
243                 ninterval = timeval_to_cputime(&value->it_interval);
244                 read_lock(&tasklist_lock);
245                 spin_lock_irq(&tsk->sighand->siglock);
246                 cval = tsk->signal->it_virt_expires;
247                 cinterval = tsk->signal->it_virt_incr;
248                 if (!cputime_eq(cval, cputime_zero) ||
249                     !cputime_eq(nval, cputime_zero)) {
250                         if (cputime_gt(nval, cputime_zero))
251                                 nval = cputime_add(nval,
252                                                    jiffies_to_cputime(1));
253                         set_process_cpu_timer(tsk, CPUCLOCK_VIRT,
254                                               &nval, &cval);
255                 }
256                 tsk->signal->it_virt_expires = nval;
257                 tsk->signal->it_virt_incr = ninterval;
258                 spin_unlock_irq(&tsk->sighand->siglock);
259                 read_unlock(&tasklist_lock);
260                 if (ovalue) {
261                         cputime_to_timeval(cval, &ovalue->it_value);
262                         cputime_to_timeval(cinterval, &ovalue->it_interval);
263                 }
264                 break;
265         case ITIMER_PROF:
266                 nval = timeval_to_cputime(&value->it_value);
267                 ninterval = timeval_to_cputime(&value->it_interval);
268                 read_lock(&tasklist_lock);
269                 spin_lock_irq(&tsk->sighand->siglock);
270                 cval = tsk->signal->it_prof_expires;
271                 cinterval = tsk->signal->it_prof_incr;
272                 if (!cputime_eq(cval, cputime_zero) ||
273                     !cputime_eq(nval, cputime_zero)) {
274                         if (cputime_gt(nval, cputime_zero))
275                                 nval = cputime_add(nval,
276                                                    jiffies_to_cputime(1));
277                         set_process_cpu_timer(tsk, CPUCLOCK_PROF,
278                                               &nval, &cval);
279                 }
280                 tsk->signal->it_prof_expires = nval;
281                 tsk->signal->it_prof_incr = ninterval;
282                 spin_unlock_irq(&tsk->sighand->siglock);
283                 read_unlock(&tasklist_lock);
284                 if (ovalue) {
285                         cputime_to_timeval(cval, &ovalue->it_value);
286                         cputime_to_timeval(cinterval, &ovalue->it_interval);
287                 }
288                 break;
289         default:
290                 return -EINVAL;
291         }
292         return 0;
293 }
294
295 /**
296  * alarm_setitimer - set alarm in seconds
297  *
298  * @seconds:    number of seconds until alarm
299  *              0 disables the alarm
300  *
301  * Returns the remaining time in seconds of a pending timer or 0 when
302  * the timer is not active.
303  *
304  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
305  * negative timeval settings which would cause immediate expiry.
306  */
307 unsigned int alarm_setitimer(unsigned int seconds)
308 {
309         struct itimerval it_new, it_old;
310
311 #if BITS_PER_LONG < 64
312         if (seconds > INT_MAX)
313                 seconds = INT_MAX;
314 #endif
315         it_new.it_value.tv_sec = seconds;
316         it_new.it_value.tv_usec = 0;
317         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
318
319         do_setitimer(ITIMER_REAL, &it_new, &it_old);
320
321         /*
322          * We can't return 0 if we have an alarm pending ...  And we'd
323          * better return too much than too little anyway
324          */
325         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
326               it_old.it_value.tv_usec >= 500000)
327                 it_old.it_value.tv_sec++;
328
329         return it_old.it_value.tv_sec;
330 }
331
332 asmlinkage long sys_setitimer(int which,
333                               struct itimerval __user *value,
334                               struct itimerval __user *ovalue)
335 {
336         struct itimerval set_buffer, get_buffer;
337         int error;
338
339         if (value) {
340                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
341                         return -EFAULT;
342         } else
343                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
344
345         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
346         if (error || !ovalue)
347                 return error;
348
349         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
350                 return -EFAULT; 
351         return 0;
352 }