Merge branch 'x86-vdso-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / fs / timerfd.c
blobf67acbdda5e8c13fce54e51f72fe0882f2fa94da
1 /*
2 * fs/timerfd.c
4 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
7 * Thanks to Thomas Gleixner for code reviews and useful comments.
9 */
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/slab.h>
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>
24 #include <linux/syscalls.h>
25 #include <linux/rcupdate.h>
27 struct timerfd_ctx {
28 struct hrtimer tmr;
29 ktime_t tintv;
30 ktime_t moffs;
31 wait_queue_head_t wqh;
32 u64 ticks;
33 int expired;
34 int clockid;
35 struct rcu_head rcu;
36 struct list_head clist;
37 bool might_cancel;
40 static LIST_HEAD(cancel_list);
41 static DEFINE_SPINLOCK(cancel_lock);
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,
46 * tintv.tv64 != 0) until the timer is accessed.
48 static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
50 struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr);
51 unsigned long flags;
53 spin_lock_irqsave(&ctx->wqh.lock, flags);
54 ctx->expired = 1;
55 ctx->ticks++;
56 wake_up_locked(&ctx->wqh);
57 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
59 return HRTIMER_NORESTART;
63 * Called when the clock was set to cancel the timers in the cancel
64 * list.
66 void timerfd_clock_was_set(void)
68 ktime_t moffs = ktime_get_monotonic_offset();
69 struct timerfd_ctx *ctx;
70 unsigned long flags;
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);
81 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
83 rcu_read_unlock();
86 static void timerfd_remove_cancel(struct timerfd_ctx *ctx)
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);
96 static bool timerfd_canceled(struct timerfd_ctx *ctx)
98 if (!ctx->might_cancel || ctx->moffs.tv64 != KTIME_MAX)
99 return false;
100 ctx->moffs = ktime_get_monotonic_offset();
101 return true;
104 static void timerfd_setup_cancel(struct timerfd_ctx *ctx, int flags)
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);
114 } else if (ctx->might_cancel) {
115 timerfd_remove_cancel(ctx);
119 static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
121 ktime_t remaining;
123 remaining = hrtimer_expires_remaining(&ctx->tmr);
124 return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
127 static int timerfd_setup(struct timerfd_ctx *ctx, int flags,
128 const struct itimerspec *ktmr)
130 enum hrtimer_mode htmode;
131 ktime_t texp;
132 int clockid = ctx->clockid;
134 htmode = (flags & TFD_TIMER_ABSTIME) ?
135 HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
137 texp = timespec_to_ktime(ktmr->it_value);
138 ctx->expired = 0;
139 ctx->ticks = 0;
140 ctx->tintv = timespec_to_ktime(ktmr->it_interval);
141 hrtimer_init(&ctx->tmr, clockid, htmode);
142 hrtimer_set_expires(&ctx->tmr, texp);
143 ctx->tmr.function = timerfd_tmrproc;
144 if (texp.tv64 != 0) {
145 hrtimer_start(&ctx->tmr, texp, htmode);
146 if (timerfd_canceled(ctx))
147 return -ECANCELED;
149 return 0;
152 static int timerfd_release(struct inode *inode, struct file *file)
154 struct timerfd_ctx *ctx = file->private_data;
156 timerfd_remove_cancel(ctx);
157 hrtimer_cancel(&ctx->tmr);
158 kfree_rcu(ctx, rcu);
159 return 0;
162 static unsigned int timerfd_poll(struct file *file, poll_table *wait)
164 struct timerfd_ctx *ctx = file->private_data;
165 unsigned int events = 0;
166 unsigned long flags;
168 poll_wait(file, &ctx->wqh, wait);
170 spin_lock_irqsave(&ctx->wqh.lock, flags);
171 if (ctx->ticks)
172 events |= POLLIN;
173 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
175 return events;
178 static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
179 loff_t *ppos)
181 struct timerfd_ctx *ctx = file->private_data;
182 ssize_t res;
183 u64 ticks = 0;
185 if (count < sizeof(ticks))
186 return -EINVAL;
187 spin_lock_irq(&ctx->wqh.lock);
188 if (file->f_flags & O_NONBLOCK)
189 res = -EAGAIN;
190 else
191 res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
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.
198 if (timerfd_canceled(ctx)) {
199 ctx->ticks = 0;
200 ctx->expired = 0;
201 res = -ECANCELED;
204 if (ctx->ticks) {
205 ticks = ctx->ticks;
207 if (ctx->expired && ctx->tintv.tv64) {
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.
214 ticks += hrtimer_forward_now(&ctx->tmr,
215 ctx->tintv) - 1;
216 hrtimer_restart(&ctx->tmr);
218 ctx->expired = 0;
219 ctx->ticks = 0;
221 spin_unlock_irq(&ctx->wqh.lock);
222 if (ticks)
223 res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
224 return res;
227 static const struct file_operations timerfd_fops = {
228 .release = timerfd_release,
229 .poll = timerfd_poll,
230 .read = timerfd_read,
231 .llseek = noop_llseek,
234 static struct file *timerfd_fget(int fd)
236 struct file *file;
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);
246 return file;
249 SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
251 int ufd;
252 struct timerfd_ctx *ctx;
254 /* Check the TFD_* constants for consistency. */
255 BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
256 BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
258 if ((flags & ~TFD_CREATE_FLAGS) ||
259 (clockid != CLOCK_MONOTONIC &&
260 clockid != CLOCK_REALTIME))
261 return -EINVAL;
263 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
264 if (!ctx)
265 return -ENOMEM;
267 init_waitqueue_head(&ctx->wqh);
268 ctx->clockid = clockid;
269 hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
270 ctx->moffs = ktime_get_monotonic_offset();
272 ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
273 O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
274 if (ufd < 0)
275 kfree(ctx);
277 return ufd;
280 SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
281 const struct itimerspec __user *, utmr,
282 struct itimerspec __user *, otmr)
284 struct file *file;
285 struct timerfd_ctx *ctx;
286 struct itimerspec ktmr, kotmr;
287 int ret;
289 if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
290 return -EFAULT;
292 if ((flags & ~TFD_SETTIME_FLAGS) ||
293 !timespec_valid(&ktmr.it_value) ||
294 !timespec_valid(&ktmr.it_interval))
295 return -EINVAL;
297 file = timerfd_fget(ufd);
298 if (IS_ERR(file))
299 return PTR_ERR(file);
300 ctx = file->private_data;
302 timerfd_setup_cancel(ctx, flags);
305 * We need to stop the existing timer before reprogramming
306 * it to the new values.
308 for (;;) {
309 spin_lock_irq(&ctx->wqh.lock);
310 if (hrtimer_try_to_cancel(&ctx->tmr) >= 0)
311 break;
312 spin_unlock_irq(&ctx->wqh.lock);
313 cpu_relax();
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.
322 if (ctx->expired && ctx->tintv.tv64)
323 hrtimer_forward_now(&ctx->tmr, ctx->tintv);
325 kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
326 kotmr.it_interval = ktime_to_timespec(ctx->tintv);
329 * Re-program the timer to the new value ...
331 ret = timerfd_setup(ctx, flags, &ktmr);
333 spin_unlock_irq(&ctx->wqh.lock);
334 fput(file);
335 if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr)))
336 return -EFAULT;
338 return ret;
341 SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
343 struct file *file;
344 struct timerfd_ctx *ctx;
345 struct itimerspec kotmr;
347 file = timerfd_fget(ufd);
348 if (IS_ERR(file))
349 return PTR_ERR(file);
350 ctx = file->private_data;
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);
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);
364 return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0;