4 * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org>
7 * Thanks to Thomas Gleixner for code reviews and useful comments.
11 #include <linux/file.h>
12 #include <linux/poll.h>
13 #include <linux/init.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>
29 wait_queue_head_t wqh;
36 * This gets called when the timer event triggers. We set the "expired"
37 * flag, but we do not re-arm the timer (in case it's necessary,
38 * tintv.tv64 != 0) until the timer is accessed.
40 static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr)
42 struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr);
45 spin_lock_irqsave(&ctx->wqh.lock, flags);
48 wake_up_locked(&ctx->wqh);
49 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
51 return HRTIMER_NORESTART;
54 static ktime_t timerfd_get_remaining(struct timerfd_ctx *ctx)
58 remaining = hrtimer_expires_remaining(&ctx->tmr);
59 return remaining.tv64 < 0 ? ktime_set(0, 0): remaining;
62 static void timerfd_setup(struct timerfd_ctx *ctx, int flags,
63 const struct itimerspec *ktmr)
65 enum hrtimer_mode htmode;
68 htmode = (flags & TFD_TIMER_ABSTIME) ?
69 HRTIMER_MODE_ABS: HRTIMER_MODE_REL;
71 texp = timespec_to_ktime(ktmr->it_value);
74 ctx->tintv = timespec_to_ktime(ktmr->it_interval);
75 hrtimer_init(&ctx->tmr, ctx->clockid, htmode);
76 hrtimer_set_expires(&ctx->tmr, texp);
77 ctx->tmr.function = timerfd_tmrproc;
79 hrtimer_start(&ctx->tmr, texp, htmode);
82 static int timerfd_release(struct inode *inode, struct file *file)
84 struct timerfd_ctx *ctx = file->private_data;
86 hrtimer_cancel(&ctx->tmr);
91 static unsigned int timerfd_poll(struct file *file, poll_table *wait)
93 struct timerfd_ctx *ctx = file->private_data;
94 unsigned int events = 0;
97 poll_wait(file, &ctx->wqh, wait);
99 spin_lock_irqsave(&ctx->wqh.lock, flags);
102 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
107 static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count,
110 struct timerfd_ctx *ctx = file->private_data;
114 if (count < sizeof(ticks))
116 spin_lock_irq(&ctx->wqh.lock);
117 if (file->f_flags & O_NONBLOCK)
120 res = wait_event_interruptible_locked_irq(ctx->wqh, ctx->ticks);
123 if (ctx->expired && ctx->tintv.tv64) {
125 * If tintv.tv64 != 0, this is a periodic timer that
126 * needs to be re-armed. We avoid doing it in the timer
127 * callback to avoid DoS attacks specifying a very
128 * short timer period.
130 ticks += hrtimer_forward_now(&ctx->tmr,
132 hrtimer_restart(&ctx->tmr);
137 spin_unlock_irq(&ctx->wqh.lock);
139 res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks);
143 static const struct file_operations timerfd_fops = {
144 .release = timerfd_release,
145 .poll = timerfd_poll,
146 .read = timerfd_read,
149 static struct file *timerfd_fget(int fd)
155 return ERR_PTR(-EBADF);
156 if (file->f_op != &timerfd_fops) {
158 return ERR_PTR(-EINVAL);
164 SYSCALL_DEFINE2(timerfd_create, int, clockid, int, flags)
167 struct timerfd_ctx *ctx;
169 /* Check the TFD_* constants for consistency. */
170 BUILD_BUG_ON(TFD_CLOEXEC != O_CLOEXEC);
171 BUILD_BUG_ON(TFD_NONBLOCK != O_NONBLOCK);
173 if ((flags & ~TFD_CREATE_FLAGS) ||
174 (clockid != CLOCK_MONOTONIC &&
175 clockid != CLOCK_REALTIME))
178 ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
182 init_waitqueue_head(&ctx->wqh);
183 ctx->clockid = clockid;
184 hrtimer_init(&ctx->tmr, clockid, HRTIMER_MODE_ABS);
186 ufd = anon_inode_getfd("[timerfd]", &timerfd_fops, ctx,
187 O_RDWR | (flags & TFD_SHARED_FCNTL_FLAGS));
194 SYSCALL_DEFINE4(timerfd_settime, int, ufd, int, flags,
195 const struct itimerspec __user *, utmr,
196 struct itimerspec __user *, otmr)
199 struct timerfd_ctx *ctx;
200 struct itimerspec ktmr, kotmr;
202 if (copy_from_user(&ktmr, utmr, sizeof(ktmr)))
205 if ((flags & ~TFD_SETTIME_FLAGS) ||
206 !timespec_valid(&ktmr.it_value) ||
207 !timespec_valid(&ktmr.it_interval))
210 file = timerfd_fget(ufd);
212 return PTR_ERR(file);
213 ctx = file->private_data;
216 * We need to stop the existing timer before reprogramming
217 * it to the new values.
220 spin_lock_irq(&ctx->wqh.lock);
221 if (hrtimer_try_to_cancel(&ctx->tmr) >= 0)
223 spin_unlock_irq(&ctx->wqh.lock);
228 * If the timer is expired and it's periodic, we need to advance it
229 * because the caller may want to know the previous expiration time.
230 * We do not update "ticks" and "expired" since the timer will be
231 * re-programmed again in the following timerfd_setup() call.
233 if (ctx->expired && ctx->tintv.tv64)
234 hrtimer_forward_now(&ctx->tmr, ctx->tintv);
236 kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
237 kotmr.it_interval = ktime_to_timespec(ctx->tintv);
240 * Re-program the timer to the new value ...
242 timerfd_setup(ctx, flags, &ktmr);
244 spin_unlock_irq(&ctx->wqh.lock);
246 if (otmr && copy_to_user(otmr, &kotmr, sizeof(kotmr)))
252 SYSCALL_DEFINE2(timerfd_gettime, int, ufd, struct itimerspec __user *, otmr)
255 struct timerfd_ctx *ctx;
256 struct itimerspec kotmr;
258 file = timerfd_fget(ufd);
260 return PTR_ERR(file);
261 ctx = file->private_data;
263 spin_lock_irq(&ctx->wqh.lock);
264 if (ctx->expired && ctx->tintv.tv64) {
267 hrtimer_forward_now(&ctx->tmr, ctx->tintv) - 1;
268 hrtimer_restart(&ctx->tmr);
270 kotmr.it_value = ktime_to_timespec(timerfd_get_remaining(ctx));
271 kotmr.it_interval = ktime_to_timespec(ctx->tintv);
272 spin_unlock_irq(&ctx->wqh.lock);
275 return copy_to_user(otmr, &kotmr, sizeof(kotmr)) ? -EFAULT: 0;