projects/linux·blob v2.6.33-rc7 · refs

298 lines · 7.3 KiB

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#include <trace/events/timer.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 */
27static 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
45static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
46 struct itimerval *const value)
47{
48 cputime_t cval, cinterval;
49 struct cpu_itimer *it = &tsk->signal->it[clock_id];
50
51 spin_lock_irq(&tsk->sighand->siglock);
52
53 cval = it->expires;
54 cinterval = it->incr;
55 if (!cputime_eq(cval, cputime_zero)) {
56 struct task_cputime cputime;
57 cputime_t t;
58
59 thread_group_cputimer(tsk, &cputime);
60 if (clock_id == CPUCLOCK_PROF)
61 t = cputime_add(cputime.utime, cputime.stime);
62 else
63 /* CPUCLOCK_VIRT */
64 t = cputime.utime;
65
66 if (cputime_le(cval, t))
67 /* about to fire */
68 cval = cputime_one_jiffy;
69 else
70 cval = cputime_sub(cval, t);
71 }
72
73 spin_unlock_irq(&tsk->sighand->siglock);
74
75 cputime_to_timeval(cval, &value->it_value);
76 cputime_to_timeval(cinterval, &value->it_interval);
77}
78
79int do_getitimer(int which, struct itimerval *value)
80{
81 struct task_struct *tsk = current;
82
83 switch (which) {
84 case ITIMER_REAL:
85 spin_lock_irq(&tsk->sighand->siglock);
86 value->it_value = itimer_get_remtime(&tsk->signal->real_timer);
87 value->it_interval =
88 ktime_to_timeval(tsk->signal->it_real_incr);
89 spin_unlock_irq(&tsk->sighand->siglock);
90 break;
91 case ITIMER_VIRTUAL:
92 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value);
93 break;
94 case ITIMER_PROF:
95 get_cpu_itimer(tsk, CPUCLOCK_PROF, value);
96 break;
97 default:
98 return(-EINVAL);
99 }
100 return 0;
101}
102
103SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value)
104{
105 int error = -EFAULT;
106 struct itimerval get_buffer;
107
108 if (value) {
109 error = do_getitimer(which, &get_buffer);
110 if (!error &&
111 copy_to_user(value, &get_buffer, sizeof(get_buffer)))
112 error = -EFAULT;
113 }
114 return error;
115}
116
117
118/*
119 * The timer is automagically restarted, when interval != 0
120 */
121enum hrtimer_restart it_real_fn(struct hrtimer *timer)
122{
123 struct signal_struct *sig =
124 container_of(timer, struct signal_struct, real_timer);
125
126 trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0);
127 kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid);
128
129 return HRTIMER_NORESTART;
130}
131
132static inline u32 cputime_sub_ns(cputime_t ct, s64 real_ns)
133{
134 struct timespec ts;
135 s64 cpu_ns;
136
137 cputime_to_timespec(ct, &ts);
138 cpu_ns = timespec_to_ns(&ts);
139
140 return (cpu_ns <= real_ns) ? 0 : cpu_ns - real_ns;
141}
142
143static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id,
144 const struct itimerval *const value,
145 struct itimerval *const ovalue)
146{
147 cputime_t cval, nval, cinterval, ninterval;
148 s64 ns_ninterval, ns_nval;
149 u32 error, incr_error;
150 struct cpu_itimer *it = &tsk->signal->it[clock_id];
151
152 nval = timeval_to_cputime(&value->it_value);
153 ns_nval = timeval_to_ns(&value->it_value);
154 ninterval = timeval_to_cputime(&value->it_interval);
155 ns_ninterval = timeval_to_ns(&value->it_interval);
156
157 error = cputime_sub_ns(nval, ns_nval);
158 incr_error = cputime_sub_ns(ninterval, ns_ninterval);
159
160 spin_lock_irq(&tsk->sighand->siglock);
161
162 cval = it->expires;
163 cinterval = it->incr;
164 if (!cputime_eq(cval, cputime_zero) ||
165 !cputime_eq(nval, cputime_zero)) {
166 if (cputime_gt(nval, cputime_zero))
167 nval = cputime_add(nval, cputime_one_jiffy);
168 set_process_cpu_timer(tsk, clock_id, &nval, &cval);
169 }
170 it->expires = nval;
171 it->incr = ninterval;
172 it->error = error;
173 it->incr_error = incr_error;
174 trace_itimer_state(clock_id == CPUCLOCK_VIRT ?
175 ITIMER_VIRTUAL : ITIMER_PROF, value, nval);
176
177 spin_unlock_irq(&tsk->sighand->siglock);
178
179 if (ovalue) {
180 cputime_to_timeval(cval, &ovalue->it_value);
181 cputime_to_timeval(cinterval, &ovalue->it_interval);
182 }
183}
184
185/*
186 * Returns true if the timeval is in canonical form
187 */
188#define timeval_valid(t) \
189 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC))
190
191int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue)
192{
193 struct task_struct *tsk = current;
194 struct hrtimer *timer;
195 ktime_t expires;
196
197 /*
198 * Validate the timevals in value.
199 */
200 if (!timeval_valid(&value->it_value) ||
201 !timeval_valid(&value->it_interval))
202 return -EINVAL;
203
204 switch (which) {
205 case ITIMER_REAL:
206again:
207 spin_lock_irq(&tsk->sighand->siglock);
208 timer = &tsk->signal->real_timer;
209 if (ovalue) {
210 ovalue->it_value = itimer_get_remtime(timer);
211 ovalue->it_interval
212 = ktime_to_timeval(tsk->signal->it_real_incr);
213 }
214 /* We are sharing ->siglock with it_real_fn() */
215 if (hrtimer_try_to_cancel(timer) < 0) {
216 spin_unlock_irq(&tsk->sighand->siglock);
217 goto again;
218 }
219 expires = timeval_to_ktime(value->it_value);
220 if (expires.tv64 != 0) {
221 tsk->signal->it_real_incr =
222 timeval_to_ktime(value->it_interval);
223 hrtimer_start(timer, expires, HRTIMER_MODE_REL);
224 } else
225 tsk->signal->it_real_incr.tv64 = 0;
226
227 trace_itimer_state(ITIMER_REAL, value, 0);
228 spin_unlock_irq(&tsk->sighand->siglock);
229 break;
230 case ITIMER_VIRTUAL:
231 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue);
232 break;
233 case ITIMER_PROF:
234 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue);
235 break;
236 default:
237 return -EINVAL;
238 }
239 return 0;
240}
241
242/**
243 * alarm_setitimer - set alarm in seconds
244 *
245 * @seconds: number of seconds until alarm
246 * 0 disables the alarm
247 *
248 * Returns the remaining time in seconds of a pending timer or 0 when
249 * the timer is not active.
250 *
251 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid
252 * negative timeval settings which would cause immediate expiry.
253 */
254unsigned int alarm_setitimer(unsigned int seconds)
255{
256 struct itimerval it_new, it_old;
257
258#if BITS_PER_LONG < 64
259 if (seconds > INT_MAX)
260 seconds = INT_MAX;
261#endif
262 it_new.it_value.tv_sec = seconds;
263 it_new.it_value.tv_usec = 0;
264 it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0;
265
266 do_setitimer(ITIMER_REAL, &it_new, &it_old);
267
268 /*
269 * We can't return 0 if we have an alarm pending ... And we'd
270 * better return too much than too little anyway
271 */
272 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) ||
273 it_old.it_value.tv_usec >= 500000)
274 it_old.it_value.tv_sec++;
275
276 return it_old.it_value.tv_sec;
277}
278
279SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value,
280 struct itimerval __user *, ovalue)
281{
282 struct itimerval set_buffer, get_buffer;
283 int error;
284
285 if (value) {
286 if(copy_from_user(&set_buffer, value, sizeof(set_buffer)))
287 return -EFAULT;
288 } else
289 memset((char *) &set_buffer, 0, sizeof(set_buffer));
290
291 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL);
292 if (error || !ovalue)
293 return error;
294
295 if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer)))
296 return -EFAULT;
297 return 0;
298}