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Source at commit fbf123cd4cc0c097fe9a99c90109ebb2a5e94a50 created 10 years 3 months ago. By Lars-Peter Clausen, dma: jz4740: Dequeue descriptor from active list before completing it | |
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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/alarmtimer.h> |
12 | #include <linux/file.h> |
13 | #include <linux/poll.h> |
14 | #include <linux/init.h> |
15 | #include <linux/fs.h> |
16 | #include <linux/sched.h> |
17 | #include <linux/kernel.h> |
18 | #include <linux/slab.h> |
19 | #include <linux/list.h> |
20 | #include <linux/spinlock.h> |
21 | #include <linux/time.h> |
22 | #include <linux/hrtimer.h> |
23 | #include <linux/anon_inodes.h> |
24 | #include <linux/timerfd.h> |
25 | #include <linux/syscalls.h> |
26 | #include <linux/compat.h> |
27 | #include <linux/rcupdate.h> |
28 | |
29 | struct timerfd_ctx { |
30 | union { |
31 | struct hrtimer tmr; |
32 | struct alarm alarm; |
33 | } t; |
34 | ktime_t tintv; |
35 | ktime_t moffs; |
36 | wait_queue_head_t wqh; |
37 | u64 ticks; |
38 | int expired; |
39 | int clockid; |
40 | struct rcu_head rcu; |
41 | struct list_head clist; |
42 | bool might_cancel; |
43 | }; |
44 | |
45 | static LIST_HEAD(cancel_list); |
46 | static DEFINE_SPINLOCK(cancel_lock); |
47 | |
48 | static inline bool isalarm(struct timerfd_ctx *ctx) |
49 | { |
50 | return ctx->clockid == CLOCK_REALTIME_ALARM || |
51 | ctx->clockid == CLOCK_BOOTTIME_ALARM; |
52 | } |
53 | |
54 | /* |
55 | * This gets called when the timer event triggers. We set the "expired" |
56 | * flag, but we do not re-arm the timer (in case it's necessary, |
57 | * tintv.tv64 != 0) until the timer is accessed. |
58 | */ |
59 | static void timerfd_triggered(struct timerfd_ctx *ctx) |
60 | { |
61 | unsigned long flags; |
62 | |
63 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
64 | ctx->expired = 1; |
65 | ctx->ticks++; |
66 | wake_up_locked(&ctx->wqh); |
67 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
68 | } |
69 | |
70 | static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr) |
71 | { |
72 | struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, |
73 | t.tmr); |
74 | timerfd_triggered(ctx); |
75 | return HRTIMER_NORESTART; |
76 | } |
77 | |
78 | static enum alarmtimer_restart timerfd_alarmproc(struct alarm *alarm, |
79 | ktime_t now) |
80 | { |
81 | struct timerfd_ctx *ctx = container_of(alarm, struct timerfd_ctx, |
82 | t.alarm); |
83 | timerfd_triggered(ctx); |
84 | return ALARMTIMER_NORESTART; |
85 | } |
86 | |
87 | /* |
88 | * Called when the clock was set to cancel the timers in the cancel |
89 | * list. This will wake up processes waiting on these timers. The |
90 | * wake-up requires ctx->ticks to be non zero, therefore we increment |
91 | * it before calling wake_up_locked(). |
92 | */ |
93 | void timerfd_clock_was_set(void) |
94 | { |
95 | ktime_t moffs = ktime_get_monotonic_offset(); |
96 | struct timerfd_ctx *ctx; |
97 | unsigned long flags; |
98 | |
99 | rcu_read_lock(); |
100 | list_for_each_entry_rcu(ctx, &cancel_list, clist) { |
101 | if (!ctx->might_cancel) |
102 | continue; |
103 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
104 | if (ctx->moffs.tv64 != moffs.tv64) { |
105 | ctx->moffs.tv64 = KTIME_MAX; |
106 | ctx->ticks++; |
107 | wake_up_locked(&ctx->wqh); |
108 | } |
109 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
110 | } |
111 | rcu_read_unlock(); |
112 | } |
113 | |
114 | static void timerfd_remove_cancel(struct timerfd_ctx *ctx) |
115 | { |
116 | if (ctx->might_cancel) { |
117 | ctx->might_cancel = false; |
118 | spin_lock(&cancel_lock); |
119 | list_del_rcu(&ctx->clist); |
120 | spin_unlock(&cancel_lock); |
121 | } |
122 | } |
123 | |
124 | static bool timerfd_canceled(struct timerfd_ctx *ctx) |
125 | { |
126 | if (!ctx->might_cancel || ctx->moffs.tv64 != KTIME_MAX) |
127 | return false; |
128 | ctx->moffs = ktime_get_monotonic_offset(); |
129 | return true; |
130 | } |
131 | |
132 | static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags) |
133 | { |
134 | if ((ctx->clockid == CLOCK_REALTIME || |
135 | ctx->clockid == CLOCK_REALTIME_ALARM) && |
136 | (flags & TFD_TIMER_ABSTIME) && (flags & TFD_TIMER_CANCEL_ON_SET)) { |
137 | if (!ctx->might_cancel) { |
138 | ctx->might_cancel = true; |
139 | spin_lock(&cancel_lock); |
140 | list_add_rcu(&ctx->clist, &cancel_list); |
141 | spin_unlock(&cancel_lock); |
142 | } |
143 | } else if (ctx->might_cancel) { |
144 | timerfd_remove_cancel(ctx); |
145 | } |
146 | } |
147 | |
148 | static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx) |
149 | { |
150 | ktime_t remaining; |
151 | |
152 | if (isalarm(ctx)) |
153 | remaining = alarm_expires_remaining(&ctx->t.alarm); |
154 | else |
155 | remaining = hrtimer_expires_remaining(&ctx->t.tmr); |
156 | |
157 | return remaining.tv64 < 0 ? ktime_set(0, 0): remaining; |
158 | } |
159 | |
160 | static int timerfd_setup(struct timerfd_ctx *ctx, int flags, |
161 | const struct itimerspec *ktmr) |
162 | { |
163 | enum hrtimer_mode htmode; |
164 | ktime_t texp; |
165 | int clockid = ctx->clockid; |
166 | |
167 | htmode = (flags & TFD_TIMER_ABSTIME) ? |
168 | HRTIMER_MODE_ABS: HRTIMER_MODE_REL; |
169 | |
170 | texp = timespec_to_ktime(ktmr->it_value); |
171 | ctx->expired = 0; |
172 | ctx->ticks = 0; |
173 | ctx->tintv = timespec_to_ktime(ktmr->it_interval); |
174 | |
175 | if (isalarm(ctx)) { |
176 | alarm_init(&ctx->t.alarm, |
177 | ctx->clockid == CLOCK_REALTIME_ALARM ? |
178 | ALARM_REALTIME : ALARM_BOOTTIME, |
179 | timerfd_alarmproc); |
180 | } else { |
181 | hrtimer_init(&ctx->t.tmr, clockid, htmode); |
182 | hrtimer_set_expires(&ctx->t.tmr, texp); |
183 | ctx->t.tmr.function = timerfd_tmrproc; |
184 | } |
185 | |
186 | if (texp.tv64 != 0) { |
187 | if (isalarm(ctx)) { |
188 | if (flags & TFD_TIMER_ABSTIME) |
189 | alarm_start(&ctx->t.alarm, texp); |
190 | else |
191 | alarm_start_relative(&ctx->t.alarm, texp); |
192 | } else { |
193 | hrtimer_start(&ctx->t.tmr, texp, htmode); |
194 | } |
195 | |
196 | if (timerfd_canceled(ctx)) |
197 | return -ECANCELED; |
198 | } |
199 | return 0; |
200 | } |
201 | |
202 | static int timerfd_release(struct inode *inode, struct file *file) |
203 | { |
204 | struct timerfd_ctx *ctx = file->private_data; |
205 | |
206 | timerfd_remove_cancel(ctx); |
207 | |
208 | if (isalarm(ctx)) |
209 | alarm_cancel(&ctx->t.alarm); |
210 | else |
211 | hrtimer_cancel(&ctx->t.tmr); |
212 | kfree_rcu(ctx, rcu); |
213 | return 0; |
214 | } |
215 | |
216 | static unsigned int timerfd_poll(struct file *file, poll_table *wait) |
217 | { |
218 | struct timerfd_ctx *ctx = file->private_data; |
219 | unsigned int events = 0; |
220 | unsigned long flags; |
221 | |
222 | poll_wait(file, &ctx->wqh, wait); |
223 | |
224 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
225 | if (ctx->ticks) |
226 | events |= POLLIN; |
227 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
228 | |
229 | return events; |
230 | } |
231 | |
232 | static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, |
233 | loff_t *ppos) |
234 | { |
235 | struct timerfd_ctx *ctx = file->private_data; |
236 | ssize_t res; |
237 | u64 ticks = 0; |
238 | |
239 | if (count < sizeof(ticks)) |
240 | return -EINVAL; |
241 | spin_lock_irq(&ctx->wqh.lock); |
242 | if (file->f_flags & O_NONBLOCK) |
243 | res = -EAGAIN; |
244 | else |
245 | res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks); |
246 | |
247 | /* |
248 | * If clock has changed, we do not care about the |
249 | * ticks and we do not rearm the timer. Userspace must |
250 | * reevaluate anyway. |
251 | */ |
252 | if (timerfd_canceled(ctx)) { |
253 | ctx->ticks = 0; |
254 | ctx->expired = 0; |
255 | res = -ECANCELED; |
256 | } |
257 | |
258 | if (ctx->ticks) { |
259 | ticks = ctx->ticks; |
260 | |
261 | if (ctx->expired && ctx->tintv.tv64) { |
262 | /* |
263 | * If tintv.tv64 != 0, this is a periodic timer that |
264 | * needs to be re-armed. We avoid doing it in the timer |
265 | * callback to avoid DoS attacks specifying a very |
266 | * short timer period. |
267 | */ |
268 | if (isalarm(ctx)) { |
269 | ticks += alarm_forward_now( |
270 | &ctx->t.alarm, ctx->tintv) - 1; |
271 | alarm_restart(&ctx->t.alarm); |
272 | } else { |
273 | ticks += hrtimer_forward_now(&ctx->t.tmr, |
274 | ctx->tintv) - 1; |
275 | hrtimer_restart(&ctx->t.tmr); |
276 | } |
277 | } |
278 | ctx->expired = 0; |
279 | ctx->ticks = 0; |
280 | } |
281 | spin_unlock_irq(&ctx->wqh.lock); |
282 | if (ticks) |
283 | res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks); |
284 | return res; |
285 | } |
286 | |
287 | static const struct file_operations timerfd_fops = { |
288 | .release = timerfd_release, |
289 | .poll = timerfd_poll, |
290 | .read = timerfd_read, |
291 | .llseek = noop_llseek, |
292 | }; |
293 | |
294 | static int timerfd_fget(int fd, struct fd *p) |
295 | { |
296 | struct fd f = fdget(fd); |
297 | if (!f.file) |
298 | return -EBADF; |
299 | if (f.file->f_op != &timerfd_fops) { |
300 | fdput(f); |
301 | return -EINVAL; |
302 | } |
303 | *p = f; |
304 | return 0; |
305 | } |
306 | |
307 | SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags) |
308 | { |
309 | int ufd; |
310 | struct timerfd_ctx *ctx; |
311 | |
312 | /* Check the TFD_* constants for consistency. */ |
313 | BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC); |
314 | BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK); |
315 | |
316 | if ((flags & ~TFD_CREATE_FLAGS) || |
317 | (clockid != CLOCK_MONOTONIC && |
318 | clockid != CLOCK_REALTIME && |
319 | clockid != CLOCK_REALTIME_ALARM && |
320 | clockid != CLOCK_BOOTTIME && |
321 | clockid != CLOCK_BOOTTIME_ALARM)) |
322 | return -EINVAL; |
323 | |
324 | ctx = kzalloc(sizeof(*ctx), GFP_KERNEL); |
325 | if (!ctx) |
326 | return -ENOMEM; |
327 | |
328 | init_waitqueue_head(&ctx->wqh); |
329 | ctx->clockid = clockid; |
330 | |
331 | if (isalarm(ctx)) |
332 | alarm_init(&ctx->t.alarm, |
333 | ctx->clockid == CLOCK_REALTIME_ALARM ? |
334 | ALARM_REALTIME : ALARM_BOOTTIME, |
335 | timerfd_alarmproc); |
336 | else |
337 | hrtimer_init(&ctx->t.tmr, clockid, HRTIMER_MODE_ABS); |
338 | |
339 | ctx->moffs = ktime_get_monotonic_offset(); |
340 | |
341 | ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx, |
342 | O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS)); |
343 | if (ufd < 0) |
344 | kfree(ctx); |
345 | |
346 | return ufd; |
347 | } |
348 | |
349 | static int do_timerfd_settime(int ufd, int flags, |
350 | const struct itimerspec *new, |
351 | struct itimerspec *old) |
352 | { |
353 | struct fd f; |
354 | struct timerfd_ctx *ctx; |
355 | int ret; |
356 | |
357 | if ((flags & ~TFD_SETTIME_FLAGS) || |
358 | !timespec_valid(&new->it_value) || |
359 | !timespec_valid(&new->it_interval)) |
360 | return -EINVAL; |
361 | |
362 | ret = timerfd_fget(ufd, &f); |
363 | if (ret) |
364 | return ret; |
365 | ctx = f.file->private_data; |
366 | |
367 | timerfd_setup_cancel(ctx, flags); |
368 | |
369 | /* |
370 | * We need to stop the existing timer before reprogramming |
371 | * it to the new values. |
372 | */ |
373 | for (;;) { |
374 | spin_lock_irq(&ctx->wqh.lock); |
375 | |
376 | if (isalarm(ctx)) { |
377 | if (alarm_try_to_cancel(&ctx->t.alarm) >= 0) |
378 | break; |
379 | } else { |
380 | if (hrtimer_try_to_cancel(&ctx->t.tmr) >= 0) |
381 | break; |
382 | } |
383 | spin_unlock_irq(&ctx->wqh.lock); |
384 | cpu_relax(); |
385 | } |
386 | |
387 | /* |
388 | * If the timer is expired and it's periodic, we need to advance it |
389 | * because the caller may want to know the previous expiration time. |
390 | * We do not update "ticks" and "expired" since the timer will be |
391 | * re-programmed again in the following timerfd_setup() call. |
392 | */ |
393 | if (ctx->expired && ctx->tintv.tv64) { |
394 | if (isalarm(ctx)) |
395 | alarm_forward_now(&ctx->t.alarm, ctx->tintv); |
396 | else |
397 | hrtimer_forward_now(&ctx->t.tmr, ctx->tintv); |
398 | } |
399 | |
400 | old->it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); |
401 | old->it_interval = ktime_to_timespec(ctx->tintv); |
402 | |
403 | /* |
404 | * Re-program the timer to the new value ... |
405 | */ |
406 | ret = timerfd_setup(ctx, flags, new); |
407 | |
408 | spin_unlock_irq(&ctx->wqh.lock); |
409 | fdput(f); |
410 | return ret; |
411 | } |
412 | |
413 | static int do_timerfd_gettime(int ufd, struct itimerspec *t) |
414 | { |
415 | struct fd f; |
416 | struct timerfd_ctx *ctx; |
417 | int ret = timerfd_fget(ufd, &f); |
418 | if (ret) |
419 | return ret; |
420 | ctx = f.file->private_data; |
421 | |
422 | spin_lock_irq(&ctx->wqh.lock); |
423 | if (ctx->expired && ctx->tintv.tv64) { |
424 | ctx->expired = 0; |
425 | |
426 | if (isalarm(ctx)) { |
427 | ctx->ticks += |
428 | alarm_forward_now( |
429 | &ctx->t.alarm, ctx->tintv) - 1; |
430 | alarm_restart(&ctx->t.alarm); |
431 | } else { |
432 | ctx->ticks += |
433 | hrtimer_forward_now(&ctx->t.tmr, ctx->tintv) |
434 | - 1; |
435 | hrtimer_restart(&ctx->t.tmr); |
436 | } |
437 | } |
438 | t->it_value = ktime_to_timespec(timerfd_get_remaining(ctx)); |
439 | t->it_interval = ktime_to_timespec(ctx->tintv); |
440 | spin_unlock_irq(&ctx->wqh.lock); |
441 | fdput(f); |
442 | return 0; |
443 | } |
444 | |
445 | SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags, |
446 | const struct itimerspec __user *, utmr, |
447 | struct itimerspec __user *, otmr) |
448 | { |
449 | struct itimerspec new, old; |
450 | int ret; |
451 | |
452 | if (copy_from_user(&new, utmr, sizeof(new))) |
453 | return -EFAULT; |
454 | ret = do_timerfd_settime(ufd, flags, &new, &old); |
455 | if (ret) |
456 | return ret; |
457 | if (otmr && copy_to_user(otmr, &old, sizeof(old))) |
458 | return -EFAULT; |
459 | |
460 | return ret; |
461 | } |
462 | |
463 | SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr) |
464 | { |
465 | struct itimerspec kotmr; |
466 | int ret = do_timerfd_gettime(ufd, &kotmr); |
467 | if (ret) |
468 | return ret; |
469 | return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0; |
470 | } |
471 | |
472 | #ifdef CONFIG_COMPAT |
473 | COMPAT_SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags, |
474 | const struct compat_itimerspec __user *, utmr, |
475 | struct compat_itimerspec __user *, otmr) |
476 | { |
477 | struct itimerspec new, old; |
478 | int ret; |
479 | |
480 | if (get_compat_itimerspec(&new, utmr)) |
481 | return -EFAULT; |
482 | ret = do_timerfd_settime(ufd, flags, &new, &old); |
483 | if (ret) |
484 | return ret; |
485 | if (otmr && put_compat_itimerspec(otmr, &old)) |
486 | return -EFAULT; |
487 | return ret; |
488 | } |
489 | |
490 | COMPAT_SYSCALL_DEFINE2(timerfd_gettime, int, ufd, |
491 | struct compat_itimerspec __user *, otmr) |
492 | { |
493 | struct itimerspec kotmr; |
494 | int ret = do_timerfd_gettime(ufd, &kotmr); |
495 | if (ret) |
496 | return ret; |
497 | return put_compat_itimerspec(otmr, &kotmr) ? -EFAULT: 0; |
498 | } |
499 | #endif |
500 |
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