]>
Commit | Line | Data |
---|---|---|
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> | |
5a0e3ad6 | 17 | #include <linux/slab.h> |
b215e283 DL |
18 | #include <linux/list.h> |
19 | #include <linux/spinlock.h> | |
20 | #include <linux/time.h> | |
21 | #include <linux/hrtimer.h> | |
22 | #include <linux/anon_inodes.h> | |
23 | #include <linux/timerfd.h> | |
45cc2b96 | 24 | #include <linux/syscalls.h> |
9ec26907 | 25 | #include <linux/rcupdate.h> |
b215e283 DL |
26 | |
27 | struct timerfd_ctx { | |
28 | struct hrtimer tmr; | |
29 | ktime_t tintv; | |
99ee5315 | 30 | ktime_t moffs; |
b215e283 | 31 | wait_queue_head_t wqh; |
4d672e7a | 32 | u64 ticks; |
b215e283 | 33 | int expired; |
4d672e7a | 34 | int clockid; |
9ec26907 TG |
35 | struct rcu_head rcu; |
36 | struct list_head clist; | |
99ee5315 | 37 | bool might_cancel; |
b215e283 DL |
38 | }; |
39 | ||
9ec26907 TG |
40 | static LIST_HEAD(cancel_list); |
41 | static DEFINE_SPINLOCK(cancel_lock); | |
42 | ||
b215e283 DL |
43 | /* |
44 | * This gets called when the timer event triggers. We set the "expired" | |
45 | * flag, but we do not re-arm the timer (in case it's necessary, | |
4d672e7a | 46 | * tintv.tv64 != 0) until the timer is accessed. |
b215e283 DL |
47 | */ |
48 | static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr) | |
49 | { | |
50 | struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr); | |
51 | unsigned long flags; | |
52 | ||
18963c01 | 53 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
b215e283 | 54 | ctx->expired = 1; |
4d672e7a | 55 | ctx->ticks++; |
b215e283 | 56 | wake_up_locked(&ctx->wqh); |
18963c01 | 57 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
b215e283 DL |
58 | |
59 | return HRTIMER_NORESTART; | |
60 | } | |
61 | ||
9ec26907 TG |
62 | /* |
63 | * Called when the clock was set to cancel the timers in the cancel | |
64 | * list. | |
65 | */ | |
66 | void timerfd_clock_was_set(void) | |
4d672e7a | 67 | { |
9ec26907 TG |
68 | ktime_t moffs = ktime_get_monotonic_offset(); |
69 | struct timerfd_ctx *ctx; | |
70 | unsigned long flags; | |
4d672e7a | 71 | |
9ec26907 TG |
72 | rcu_read_lock(); |
73 | list_for_each_entry_rcu(ctx, &cancel_list, clist) { | |
74 | if (!ctx->might_cancel) | |
75 | continue; | |
76 | spin_lock_irqsave(&ctx->wqh.lock, flags); | |
77 | if (ctx->moffs.tv64 != moffs.tv64) { | |
78 | ctx->moffs.tv64 = KTIME_MAX; | |
79 | wake_up_locked(&ctx->wqh); | |
80 | } | |
81 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); | |
82 | } | |
83 | rcu_read_unlock(); | |
4d672e7a DL |
84 | } |
85 | ||
9ec26907 | 86 | static void timerfd_remove_cancel(struct timerfd_ctx *ctx) |
99ee5315 | 87 | { |
9ec26907 TG |
88 | if (ctx->might_cancel) { |
89 | ctx->might_cancel = false; | |
90 | spin_lock(&cancel_lock); | |
91 | list_del_rcu(&ctx->clist); | |
92 | spin_unlock(&cancel_lock); | |
93 | } | |
94 | } | |
99ee5315 | 95 | |
9ec26907 TG |
96 | static bool timerfd_canceled(struct timerfd_ctx *ctx) |
97 | { | |
98 | if (!ctx->might_cancel || ctx->moffs.tv64 != KTIME_MAX) | |
99ee5315 | 99 | return false; |
9ec26907 TG |
100 | ctx->moffs = ktime_get_monotonic_offset(); |
101 | return true; | |
102 | } | |
99ee5315 | 103 | |
9ec26907 TG |
104 | static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags) |
105 | { | |
106 | if (ctx->clockid == CLOCK_REALTIME && (flags & TFD_TIMER_ABSTIME) && | |
107 | (flags & TFD_TIMER_CANCEL_ON_SET)) { | |
108 | if (!ctx->might_cancel) { | |
109 | ctx->might_cancel = true; | |
110 | spin_lock(&cancel_lock); | |
111 | list_add_rcu(&ctx->clist, &cancel_list); | |
112 | spin_unlock(&cancel_lock); | |
113 | } | |
114 | } else if (ctx->might_cancel) { | |
115 | timerfd_remove_cancel(ctx); | |
116 | } | |
117 | } | |
99ee5315 | 118 | |
9ec26907 TG |
119 | static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx) |
120 | { | |
121 | ktime_t remaining; | |
99ee5315 | 122 | |
9ec26907 TG |
123 | remaining = hrtimer_expires_remaining(&ctx->tmr); |
124 | return remaining.tv64 < 0 ? ktime_set(0, 0): remaining; | |
99ee5315 TG |
125 | } |
126 | ||
127 | static int timerfd_setup(struct timerfd_ctx *ctx, int flags, | |
128 | const struct itimerspec *ktmr) | |
b215e283 DL |
129 | { |
130 | enum hrtimer_mode htmode; | |
131 | ktime_t texp; | |
99ee5315 | 132 | int clockid = ctx->clockid; |
b215e283 DL |
133 | |
134 | htmode = (flags & TFD_TIMER_ABSTIME) ? | |
135 | HRTIMER_MODE_ABS: HRTIMER_MODE_REL; | |
136 | ||
137 | texp = timespec_to_ktime(ktmr->it_value); | |
138 | ctx->expired = 0; | |
4d672e7a | 139 | ctx->ticks = 0; |
b215e283 | 140 | ctx->tintv = timespec_to_ktime(ktmr->it_interval); |
99ee5315 | 141 | hrtimer_init(&ctx->tmr, clockid, htmode); |
76369470 | 142 | hrtimer_set_expires(&ctx->tmr, texp); |
b215e283 | 143 | ctx->tmr.function = timerfd_tmrproc; |
99ee5315 | 144 | if (texp.tv64 != 0) { |
b215e283 | 145 | hrtimer_start(&ctx->tmr, texp, htmode); |
99ee5315 TG |
146 | if (timerfd_canceled(ctx)) |
147 | return -ECANCELED; | |
148 | } | |
149 | return 0; | |
b215e283 DL |
150 | } |
151 | ||
152 | static int timerfd_release(struct inode *inode, struct file *file) | |
153 | { | |
154 | struct timerfd_ctx *ctx = file->private_data; | |
155 | ||
9ec26907 | 156 | timerfd_remove_cancel(ctx); |
b215e283 | 157 | hrtimer_cancel(&ctx->tmr); |
9ec26907 | 158 | kfree_rcu(ctx, rcu); |
b215e283 DL |
159 | return 0; |
160 | } | |
161 | ||
162 | static unsigned int timerfd_poll(struct file *file, poll_table *wait) | |
163 | { | |
164 | struct timerfd_ctx *ctx = file->private_data; | |
165 | unsigned int events = 0; | |
166 | unsigned long flags; | |
167 | ||
168 | poll_wait(file, &ctx->wqh, wait); | |
169 | ||
18963c01 | 170 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
4d672e7a | 171 | if (ctx->ticks) |
b215e283 | 172 | events |= POLLIN; |
18963c01 | 173 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
b215e283 DL |
174 | |
175 | return events; | |
176 | } | |
177 | ||
178 | static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, | |
179 | loff_t *ppos) | |
180 | { | |
181 | struct timerfd_ctx *ctx = file->private_data; | |
182 | ssize_t res; | |
09828402 | 183 | u64 ticks = 0; |
b215e283 DL |
184 | |
185 | if (count < sizeof(ticks)) | |
186 | return -EINVAL; | |
18963c01 | 187 | spin_lock_irq(&ctx->wqh.lock); |
8120a8aa MN |
188 | if (file->f_flags & O_NONBLOCK) |
189 | res = -EAGAIN; | |
190 | else | |
191 | res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks); | |
99ee5315 | 192 | |
9ec26907 TG |
193 | /* |
194 | * If clock has changed, we do not care about the | |
195 | * ticks and we do not rearm the timer. Userspace must | |
196 | * reevaluate anyway. | |
197 | */ | |
198 | if (timerfd_canceled(ctx)) { | |
199 | ctx->ticks = 0; | |
200 | ctx->expired = 0; | |
201 | res = -ECANCELED; | |
202 | } | |
203 | ||
4d672e7a DL |
204 | if (ctx->ticks) { |
205 | ticks = ctx->ticks; | |
99ee5315 | 206 | |
4d672e7a | 207 | if (ctx->expired && ctx->tintv.tv64) { |
b215e283 DL |
208 | /* |
209 | * If tintv.tv64 != 0, this is a periodic timer that | |
210 | * needs to be re-armed. We avoid doing it in the timer | |
211 | * callback to avoid DoS attacks specifying a very | |
212 | * short timer period. | |
213 | */ | |
4d672e7a DL |
214 | ticks += hrtimer_forward_now(&ctx->tmr, |
215 | ctx->tintv) - 1; | |
b215e283 | 216 | hrtimer_restart(&ctx->tmr); |
4d672e7a DL |
217 | } |
218 | ctx->expired = 0; | |
219 | ctx->ticks = 0; | |
b215e283 | 220 | } |
18963c01 | 221 | spin_unlock_irq(&ctx->wqh.lock); |
b215e283 | 222 | if (ticks) |
09828402 | 223 | res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks); |
b215e283 DL |
224 | return res; |
225 | } | |
226 | ||
227 | static const struct file_operations timerfd_fops = { | |
228 | .release = timerfd_release, | |
229 | .poll = timerfd_poll, | |
230 | .read = timerfd_read, | |
6038f373 | 231 | .llseek = noop_llseek, |
b215e283 DL |
232 | }; |
233 | ||
4d672e7a DL |
234 | static struct file *timerfd_fget(int fd) |
235 | { | |
236 | struct file *file; | |
237 | ||
238 | file = fget(fd); | |
239 | if (!file) | |
240 | return ERR_PTR(-EBADF); | |
241 | if (file->f_op != &timerfd_fops) { | |
242 | fput(file); | |
243 | return ERR_PTR(-EINVAL); | |
244 | } | |
245 | ||
246 | return file; | |
247 | } | |
248 | ||
836f92ad | 249 | SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags) |
b215e283 | 250 | { |
2030a42c | 251 | int ufd; |
b215e283 | 252 | struct timerfd_ctx *ctx; |
b215e283 | 253 | |
e38b36f3 UD |
254 | /* Check the TFD_* constants for consistency. */ |
255 | BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC); | |
256 | BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK); | |
257 | ||
610d18f4 DL |
258 | if ((flags & ~TFD_CREATE_FLAGS) || |
259 | (clockid != CLOCK_MONOTONIC && | |
260 | clockid != CLOCK_REALTIME)) | |
b215e283 | 261 | return -EINVAL; |
4d672e7a DL |
262 | |
263 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); | |
264 | if (!ctx) | |
265 | return -ENOMEM; | |
266 | ||
267 | init_waitqueue_head(&ctx->wqh); | |
268 | ctx->clockid = clockid; | |
269 | hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS); | |
99ee5315 | 270 | ctx->moffs = ktime_get_monotonic_offset(); |
4d672e7a | 271 | |
11fcb6c1 | 272 | ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx, |
628ff7c1 | 273 | O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS)); |
2030a42c | 274 | if (ufd < 0) |
4d672e7a | 275 | kfree(ctx); |
4d672e7a DL |
276 | |
277 | return ufd; | |
278 | } | |
279 | ||
836f92ad HC |
280 | SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags, |
281 | const struct itimerspec __user *, utmr, | |
282 | struct itimerspec __user *, otmr) | |
4d672e7a DL |
283 | { |
284 | struct file *file; | |
285 | struct timerfd_ctx *ctx; | |
286 | struct itimerspec ktmr, kotmr; | |
99ee5315 | 287 | int ret; |
4d672e7a DL |
288 | |
289 | if (copy_from_user(&ktmr, utmr, sizeof(ktmr))) | |
290 | return -EFAULT; | |
291 | ||
610d18f4 DL |
292 | if ((flags & ~TFD_SETTIME_FLAGS) || |
293 | !timespec_valid(&ktmr.it_value) || | |
b215e283 DL |
294 | !timespec_valid(&ktmr.it_interval)) |
295 | return -EINVAL; | |
296 | ||
4d672e7a DL |
297 | file = timerfd_fget(ufd); |
298 | if (IS_ERR(file)) | |
299 | return PTR_ERR(file); | |
300 | ctx = file->private_data; | |
b215e283 | 301 | |
9ec26907 TG |
302 | timerfd_setup_cancel(ctx, flags); |
303 | ||
4d672e7a DL |
304 | /* |
305 | * We need to stop the existing timer before reprogramming | |
306 | * it to the new values. | |
307 | */ | |
308 | for (;;) { | |
309 | spin_lock_irq(&ctx->wqh.lock); | |
310 | if (hrtimer_try_to_cancel(&ctx->tmr) >= 0) | |
311 | break; | |
18963c01 | 312 | spin_unlock_irq(&ctx->wqh.lock); |
4d672e7a | 313 | cpu_relax(); |
b215e283 DL |
314 | } |
315 | ||
4d672e7a DL |
316 | /* |
317 | * If the timer is expired and it's periodic, we need to advance it | |
318 | * because the caller may want to know the previous expiration time. | |
319 | * We do not update "ticks" and "expired" since the timer will be | |
320 | * re-programmed again in the following timerfd_setup() call. | |
321 | */ | |
322 | if (ctx->expired && ctx->tintv.tv64) | |
323 | hrtimer_forward_now(&ctx->tmr, ctx->tintv); | |
b215e283 | 324 | |
4d672e7a DL |
325 | kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); |
326 | kotmr.it_interval = ktime_to_timespec(ctx->tintv); | |
327 | ||
328 | /* | |
329 | * Re-program the timer to the new value ... | |
330 | */ | |
99ee5315 | 331 | ret = timerfd_setup(ctx, flags, &ktmr); |
4d672e7a DL |
332 | |
333 | spin_unlock_irq(&ctx->wqh.lock); | |
334 | fput(file); | |
335 | if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr))) | |
336 | return -EFAULT; | |
337 | ||
99ee5315 | 338 | return ret; |
4d672e7a DL |
339 | } |
340 | ||
d4e82042 | 341 | SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr) |
4d672e7a DL |
342 | { |
343 | struct file *file; | |
344 | struct timerfd_ctx *ctx; | |
345 | struct itimerspec kotmr; | |
346 | ||
347 | file = timerfd_fget(ufd); | |
348 | if (IS_ERR(file)) | |
349 | return PTR_ERR(file); | |
350 | ctx = file->private_data; | |
351 | ||
352 | spin_lock_irq(&ctx->wqh.lock); | |
353 | if (ctx->expired && ctx->tintv.tv64) { | |
354 | ctx->expired = 0; | |
355 | ctx->ticks += | |
356 | hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1; | |
357 | hrtimer_restart(&ctx->tmr); | |
358 | } | |
359 | kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); | |
360 | kotmr.it_interval = ktime_to_timespec(ctx->tintv); | |
361 | spin_unlock_irq(&ctx->wqh.lock); | |
362 | fput(file); | |
363 | ||
364 | return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0; | |
b215e283 DL |
365 | } |
366 |