cputime: Optimize jiffies_to_cputime(1)
[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/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 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
45                            struct itimerval *const value)
46 {
47         cputime_t cval, cinterval;
48         struct cpu_itimer *it = &tsk->signal->it[clock_id];
49
50         spin_lock_irq(&tsk->sighand->siglock);
51
52         cval = it->expires;
53         cinterval = it->incr;
54         if (!cputime_eq(cval, cputime_zero)) {
55                 struct task_cputime cputime;
56                 cputime_t t;
57
58                 thread_group_cputimer(tsk, &cputime);
59                 if (clock_id == CPUCLOCK_PROF)
60                         t = cputime_add(cputime.utime, cputime.stime);
61                 else
62                         /* CPUCLOCK_VIRT */
63                         t = cputime.utime;
64
65                 if (cputime_le(cval, t))
66                         /* about to fire */
67                         cval = cputime_one_jiffy;
68                 else
69                         cval = cputime_sub(cval, t);
70         }
71
72         spin_unlock_irq(&tsk->sighand->siglock);
73
74         cputime_to_timeval(cval, &value->it_value);
75         cputime_to_timeval(cinterval, &value->it_interval);
76 }
77
78 int do_getitimer(int which, struct itimerval *value)
79 {
80         struct task_struct *tsk = current;
81
82         switch (which) {
83         case ITIMER_REAL:
84                 spin_lock_irq(&tsk->sighand->siglock);
85                 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
86                 value->it_interval =
87                         ktime_to_timeval(tsk->signal->it_real_incr);
88                 spin_unlock_irq(&tsk->sighand->siglock);
89                 break;
90         case ITIMER_VIRTUAL:
91                 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
92                 break;
93         case ITIMER_PROF:
94                 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
95                 break;
96         default:
97                 return(-EINVAL);
98         }
99         return 0;
100 }
101
102 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
103 {
104         int error = -EFAULT;
105         struct itimerval get_buffer;
106
107         if (value) {
108                 error = do_getitimer(which, &get_buffer);
109                 if (!error &&
110                     copy_to_user(value, &get_buffer, sizeof(get_buffer)))
111                         error = -EFAULT;
112         }
113         return error;
114 }
115
116
117 /*
118  * The timer is automagically restarted, when interval != 0
119  */
120 enum hrtimer_restart it_real_fn(struct hrtimer *timer)
121 {
122         struct signal_struct *sig =
123                 container_of(timer, struct signal_struct, real_timer);
124
125         kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
126
127         return HRTIMER_NORESTART;
128 }
129
130 static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
131 {
132         struct timespec ts;
133         s64 cpu_ns;
134
135         cputime_to_timespec(ct, &ts);
136         cpu_ns = timespec_to_ns(&ts);
137
138         return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
139 }
140
141 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
142                            const struct itimerval *const value,
143                            struct itimerval *const ovalue)
144 {
145         cputime_t cval, nval, cinterval, ninterval;
146         s64 ns_ninterval, ns_nval;
147         struct cpu_itimer *it = &tsk->signal->it[clock_id];
148
149         nval = timeval_to_cputime(&value->it_value);
150         ns_nval = timeval_to_ns(&value->it_value);
151         ninterval = timeval_to_cputime(&value->it_interval);
152         ns_ninterval = timeval_to_ns(&value->it_interval);
153
154         it->incr_error = cputime_sub_ns(ninterval, ns_ninterval);
155         it->error = cputime_sub_ns(nval, ns_nval);
156
157         spin_lock_irq(&tsk->sighand->siglock);
158
159         cval = it->expires;
160         cinterval = it->incr;
161         if (!cputime_eq(cval, cputime_zero) ||
162             !cputime_eq(nval, cputime_zero)) {
163                 if (cputime_gt(nval, cputime_zero))
164                         nval = cputime_add(nval, cputime_one_jiffy);
165                 set_process_cpu_timer(tsk, clock_id, &nval, &cval);
166         }
167         it->expires = nval;
168         it->incr = ninterval;
169
170         spin_unlock_irq(&tsk->sighand->siglock);
171
172         if (ovalue) {
173                 cputime_to_timeval(cval, &ovalue->it_value);
174                 cputime_to_timeval(cinterval, &ovalue->it_interval);
175         }
176 }
177
178 /*
179  * Returns true if the timeval is in canonical form
180  */
181 #define timeval_valid(t) \
182         (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
183
184 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
185 {
186         struct task_struct *tsk = current;
187         struct hrtimer *timer;
188         ktime_t expires;
189
190         /*
191          * Validate the timevals in value.
192          */
193         if (!timeval_valid(&value->it_value) ||
194             !timeval_valid(&value->it_interval))
195                 return -EINVAL;
196
197         switch (which) {
198         case ITIMER_REAL:
199 again:
200                 spin_lock_irq(&tsk->sighand->siglock);
201                 timer = &tsk->signal->real_timer;
202                 if (ovalue) {
203                         ovalue->it_value = itimer_get_remtime(timer);
204                         ovalue->it_interval
205                                 = ktime_to_timeval(tsk->signal->it_real_incr);
206                 }
207                 /* We are sharing ->siglock with it_real_fn() */
208                 if (hrtimer_try_to_cancel(timer) < 0) {
209                         spin_unlock_irq(&tsk->sighand->siglock);
210                         goto again;
211                 }
212                 expires = timeval_to_ktime(value->it_value);
213                 if (expires.tv64 != 0) {
214                         tsk->signal->it_real_incr =
215                                 timeval_to_ktime(value->it_interval);
216                         hrtimer_start(timer, expires, HRTIMER_MODE_REL);
217                 } else
218                         tsk->signal->it_real_incr.tv64 = 0;
219
220                 spin_unlock_irq(&tsk->sighand->siglock);
221                 break;
222         case ITIMER_VIRTUAL:
223                 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
224                 break;
225         case ITIMER_PROF:
226                 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
227                 break;
228         default:
229                 return -EINVAL;
230         }
231         return 0;
232 }
233
234 /**
235  * alarm_setitimer - set alarm in seconds
236  *
237  * @seconds:    number of seconds until alarm
238  *              0 disables the alarm
239  *
240  * Returns the remaining time in seconds of a pending timer or 0 when
241  * the timer is not active.
242  *
243  * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
244  * negative timeval settings which would cause immediate expiry.
245  */
246 unsigned int alarm_setitimer(unsigned int seconds)
247 {
248         struct itimerval it_new, it_old;
249
250 #if BITS_PER_LONG < 64
251         if (seconds > INT_MAX)
252                 seconds = INT_MAX;
253 #endif
254         it_new.it_value.tv_sec = seconds;
255         it_new.it_value.tv_usec = 0;
256         it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
257
258         do_setitimer(ITIMER_REAL, &it_new, &it_old);
259
260         /*
261          * We can't return 0 if we have an alarm pending ...  And we'd
262          * better return too much than too little anyway
263          */
264         if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
265               it_old.it_value.tv_usec >= 500000)
266                 it_old.it_value.tv_sec++;
267
268         return it_old.it_value.tv_sec;
269 }
270
271 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
272                 struct itimerval __user *, ovalue)
273 {
274         struct itimerval set_buffer, get_buffer;
275         int error;
276
277         if (value) {
278                 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
279                         return -EFAULT;
280         } else
281                 memset((char *) &set_buffer, 0, sizeof(set_buffer));
282
283         error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
284         if (error || !ovalue)
285                 return error;
286
287         if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
288                 return -EFAULT;
289         return 0;
290 }