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b215e283 DL |
1 | /* |
2 | * fs/timerfd.c | |
3 | * | |
4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> | |
5 | * | |
6 | * | |
7 | * Thanks to Thomas Gleixner for code reviews and useful comments. | |
8 | * | |
9 | */ | |
10 | ||
11 | #include <linux/file.h> | |
12 | #include <linux/poll.h> | |
13 | #include <linux/init.h> | |
14 | #include <linux/fs.h> | |
15 | #include <linux/sched.h> | |
16 | #include <linux/kernel.h> | |
17 | #include <linux/list.h> | |
18 | #include <linux/spinlock.h> | |
19 | #include <linux/time.h> | |
20 | #include <linux/hrtimer.h> | |
21 | #include <linux/anon_inodes.h> | |
22 | #include <linux/timerfd.h> | |
23 | ||
24 | struct timerfd_ctx { | |
25 | struct hrtimer tmr; | |
26 | ktime_t tintv; | |
b215e283 | 27 | wait_queue_head_t wqh; |
4d672e7a | 28 | u64 ticks; |
b215e283 | 29 | int expired; |
4d672e7a | 30 | int clockid; |
b215e283 DL |
31 | }; |
32 | ||
33 | /* | |
34 | * This gets called when the timer event triggers. We set the "expired" | |
35 | * flag, but we do not re-arm the timer (in case it's necessary, | |
4d672e7a | 36 | * tintv.tv64 != 0) until the timer is accessed. |
b215e283 DL |
37 | */ |
38 | static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr) | |
39 | { | |
40 | struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr); | |
41 | unsigned long flags; | |
42 | ||
18963c01 | 43 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
b215e283 | 44 | ctx->expired = 1; |
4d672e7a | 45 | ctx->ticks++; |
b215e283 | 46 | wake_up_locked(&ctx->wqh); |
18963c01 | 47 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
b215e283 DL |
48 | |
49 | return HRTIMER_NORESTART; | |
50 | } | |
51 | ||
4d672e7a DL |
52 | static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx) |
53 | { | |
54 | ktime_t now, remaining; | |
55 | ||
56 | now = ctx->tmr.base->get_time(); | |
57 | remaining = ktime_sub(ctx->tmr.expires, now); | |
58 | ||
59 | return remaining.tv64 < 0 ? ktime_set(0, 0): remaining; | |
60 | } | |
61 | ||
62 | static void timerfd_setup(struct timerfd_ctx *ctx, int flags, | |
b215e283 DL |
63 | const struct itimerspec *ktmr) |
64 | { | |
65 | enum hrtimer_mode htmode; | |
66 | ktime_t texp; | |
67 | ||
68 | htmode = (flags & TFD_TIMER_ABSTIME) ? | |
69 | HRTIMER_MODE_ABS: HRTIMER_MODE_REL; | |
70 | ||
71 | texp = timespec_to_ktime(ktmr->it_value); | |
72 | ctx->expired = 0; | |
4d672e7a | 73 | ctx->ticks = 0; |
b215e283 | 74 | ctx->tintv = timespec_to_ktime(ktmr->it_interval); |
4d672e7a | 75 | hrtimer_init(&ctx->tmr, ctx->clockid, htmode); |
b215e283 DL |
76 | ctx->tmr.expires = texp; |
77 | ctx->tmr.function = timerfd_tmrproc; | |
78 | if (texp.tv64 != 0) | |
79 | hrtimer_start(&ctx->tmr, texp, htmode); | |
80 | } | |
81 | ||
82 | static int timerfd_release(struct inode *inode, struct file *file) | |
83 | { | |
84 | struct timerfd_ctx *ctx = file->private_data; | |
85 | ||
86 | hrtimer_cancel(&ctx->tmr); | |
87 | kfree(ctx); | |
88 | return 0; | |
89 | } | |
90 | ||
91 | static unsigned int timerfd_poll(struct file *file, poll_table *wait) | |
92 | { | |
93 | struct timerfd_ctx *ctx = file->private_data; | |
94 | unsigned int events = 0; | |
95 | unsigned long flags; | |
96 | ||
97 | poll_wait(file, &ctx->wqh, wait); | |
98 | ||
18963c01 | 99 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
4d672e7a | 100 | if (ctx->ticks) |
b215e283 | 101 | events |= POLLIN; |
18963c01 | 102 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
b215e283 DL |
103 | |
104 | return events; | |
105 | } | |
106 | ||
107 | static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, | |
108 | loff_t *ppos) | |
109 | { | |
110 | struct timerfd_ctx *ctx = file->private_data; | |
111 | ssize_t res; | |
09828402 | 112 | u64 ticks = 0; |
b215e283 DL |
113 | DECLARE_WAITQUEUE(wait, current); |
114 | ||
115 | if (count < sizeof(ticks)) | |
116 | return -EINVAL; | |
18963c01 | 117 | spin_lock_irq(&ctx->wqh.lock); |
b215e283 | 118 | res = -EAGAIN; |
4d672e7a | 119 | if (!ctx->ticks && !(file->f_flags & O_NONBLOCK)) { |
b215e283 DL |
120 | __add_wait_queue(&ctx->wqh, &wait); |
121 | for (res = 0;;) { | |
122 | set_current_state(TASK_INTERRUPTIBLE); | |
4d672e7a | 123 | if (ctx->ticks) { |
b215e283 DL |
124 | res = 0; |
125 | break; | |
126 | } | |
127 | if (signal_pending(current)) { | |
128 | res = -ERESTARTSYS; | |
129 | break; | |
130 | } | |
18963c01 | 131 | spin_unlock_irq(&ctx->wqh.lock); |
b215e283 | 132 | schedule(); |
18963c01 | 133 | spin_lock_irq(&ctx->wqh.lock); |
b215e283 DL |
134 | } |
135 | __remove_wait_queue(&ctx->wqh, &wait); | |
136 | __set_current_state(TASK_RUNNING); | |
137 | } | |
4d672e7a DL |
138 | if (ctx->ticks) { |
139 | ticks = ctx->ticks; | |
140 | if (ctx->expired && ctx->tintv.tv64) { | |
b215e283 DL |
141 | /* |
142 | * If tintv.tv64 != 0, this is a periodic timer that | |
143 | * needs to be re-armed. We avoid doing it in the timer | |
144 | * callback to avoid DoS attacks specifying a very | |
145 | * short timer period. | |
146 | */ | |
4d672e7a DL |
147 | ticks += hrtimer_forward_now(&ctx->tmr, |
148 | ctx->tintv) - 1; | |
b215e283 | 149 | hrtimer_restart(&ctx->tmr); |
4d672e7a DL |
150 | } |
151 | ctx->expired = 0; | |
152 | ctx->ticks = 0; | |
b215e283 | 153 | } |
18963c01 | 154 | spin_unlock_irq(&ctx->wqh.lock); |
b215e283 | 155 | if (ticks) |
09828402 | 156 | res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks); |
b215e283 DL |
157 | return res; |
158 | } | |
159 | ||
160 | static const struct file_operations timerfd_fops = { | |
161 | .release = timerfd_release, | |
162 | .poll = timerfd_poll, | |
163 | .read = timerfd_read, | |
164 | }; | |
165 | ||
4d672e7a DL |
166 | static struct file *timerfd_fget(int fd) |
167 | { | |
168 | struct file *file; | |
169 | ||
170 | file = fget(fd); | |
171 | if (!file) | |
172 | return ERR_PTR(-EBADF); | |
173 | if (file->f_op != &timerfd_fops) { | |
174 | fput(file); | |
175 | return ERR_PTR(-EINVAL); | |
176 | } | |
177 | ||
178 | return file; | |
179 | } | |
180 | ||
181 | asmlinkage long sys_timerfd_create(int clockid, int flags) | |
b215e283 | 182 | { |
4d672e7a | 183 | int error, ufd; |
b215e283 DL |
184 | struct timerfd_ctx *ctx; |
185 | struct file *file; | |
186 | struct inode *inode; | |
b215e283 | 187 | |
4d672e7a DL |
188 | if (flags) |
189 | return -EINVAL; | |
b215e283 DL |
190 | if (clockid != CLOCK_MONOTONIC && |
191 | clockid != CLOCK_REALTIME) | |
192 | return -EINVAL; | |
4d672e7a DL |
193 | |
194 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); | |
195 | if (!ctx) | |
196 | return -ENOMEM; | |
197 | ||
198 | init_waitqueue_head(&ctx->wqh); | |
199 | ctx->clockid = clockid; | |
200 | hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS); | |
201 | ||
202 | error = anon_inode_getfd(&ufd, &inode, &file, "[timerfd]", | |
203 | &timerfd_fops, ctx); | |
204 | if (error) { | |
205 | kfree(ctx); | |
206 | return error; | |
207 | } | |
208 | ||
209 | return ufd; | |
210 | } | |
211 | ||
212 | asmlinkage long sys_timerfd_settime(int ufd, int flags, | |
213 | const struct itimerspec __user *utmr, | |
214 | struct itimerspec __user *otmr) | |
215 | { | |
216 | struct file *file; | |
217 | struct timerfd_ctx *ctx; | |
218 | struct itimerspec ktmr, kotmr; | |
219 | ||
220 | if (copy_from_user(&ktmr, utmr, sizeof(ktmr))) | |
221 | return -EFAULT; | |
222 | ||
b215e283 DL |
223 | if (!timespec_valid(&ktmr.it_value) || |
224 | !timespec_valid(&ktmr.it_interval)) | |
225 | return -EINVAL; | |
226 | ||
4d672e7a DL |
227 | file = timerfd_fget(ufd); |
228 | if (IS_ERR(file)) | |
229 | return PTR_ERR(file); | |
230 | ctx = file->private_data; | |
b215e283 | 231 | |
4d672e7a DL |
232 | /* |
233 | * We need to stop the existing timer before reprogramming | |
234 | * it to the new values. | |
235 | */ | |
236 | for (;;) { | |
237 | spin_lock_irq(&ctx->wqh.lock); | |
238 | if (hrtimer_try_to_cancel(&ctx->tmr) >= 0) | |
239 | break; | |
18963c01 | 240 | spin_unlock_irq(&ctx->wqh.lock); |
4d672e7a | 241 | cpu_relax(); |
b215e283 DL |
242 | } |
243 | ||
4d672e7a DL |
244 | /* |
245 | * If the timer is expired and it's periodic, we need to advance it | |
246 | * because the caller may want to know the previous expiration time. | |
247 | * We do not update "ticks" and "expired" since the timer will be | |
248 | * re-programmed again in the following timerfd_setup() call. | |
249 | */ | |
250 | if (ctx->expired && ctx->tintv.tv64) | |
251 | hrtimer_forward_now(&ctx->tmr, ctx->tintv); | |
b215e283 | 252 | |
4d672e7a DL |
253 | kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); |
254 | kotmr.it_interval = ktime_to_timespec(ctx->tintv); | |
255 | ||
256 | /* | |
257 | * Re-program the timer to the new value ... | |
258 | */ | |
259 | timerfd_setup(ctx, flags, &ktmr); | |
260 | ||
261 | spin_unlock_irq(&ctx->wqh.lock); | |
262 | fput(file); | |
263 | if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr))) | |
264 | return -EFAULT; | |
265 | ||
266 | return 0; | |
267 | } | |
268 | ||
269 | asmlinkage long sys_timerfd_gettime(int ufd, struct itimerspec __user *otmr) | |
270 | { | |
271 | struct file *file; | |
272 | struct timerfd_ctx *ctx; | |
273 | struct itimerspec kotmr; | |
274 | ||
275 | file = timerfd_fget(ufd); | |
276 | if (IS_ERR(file)) | |
277 | return PTR_ERR(file); | |
278 | ctx = file->private_data; | |
279 | ||
280 | spin_lock_irq(&ctx->wqh.lock); | |
281 | if (ctx->expired && ctx->tintv.tv64) { | |
282 | ctx->expired = 0; | |
283 | ctx->ticks += | |
284 | hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1; | |
285 | hrtimer_restart(&ctx->tmr); | |
286 | } | |
287 | kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); | |
288 | kotmr.it_interval = ktime_to_timespec(ctx->tintv); | |
289 | spin_unlock_irq(&ctx->wqh.lock); | |
290 | fput(file); | |
291 | ||
292 | return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0; | |
b215e283 DL |
293 | } |
294 |