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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 DL |
27 | wait_queue_head_t wqh; |
28 | int expired; | |
29 | }; | |
30 | ||
31 | /* | |
32 | * This gets called when the timer event triggers. We set the "expired" | |
33 | * flag, but we do not re-arm the timer (in case it's necessary, | |
34 | * tintv.tv64 != 0) until the timer is read. | |
35 | */ | |
36 | static enum hrtimer_restart timerfd_tmrproc(struct hrtimer *htmr) | |
37 | { | |
38 | struct timerfd_ctx *ctx = container_of(htmr, struct timerfd_ctx, tmr); | |
39 | unsigned long flags; | |
40 | ||
18963c01 | 41 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
b215e283 DL |
42 | ctx->expired = 1; |
43 | wake_up_locked(&ctx->wqh); | |
18963c01 | 44 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
b215e283 DL |
45 | |
46 | return HRTIMER_NORESTART; | |
47 | } | |
48 | ||
49 | static void timerfd_setup(struct timerfd_ctx *ctx, int clockid, int flags, | |
50 | const struct itimerspec *ktmr) | |
51 | { | |
52 | enum hrtimer_mode htmode; | |
53 | ktime_t texp; | |
54 | ||
55 | htmode = (flags & TFD_TIMER_ABSTIME) ? | |
56 | HRTIMER_MODE_ABS: HRTIMER_MODE_REL; | |
57 | ||
58 | texp = timespec_to_ktime(ktmr->it_value); | |
59 | ctx->expired = 0; | |
60 | ctx->tintv = timespec_to_ktime(ktmr->it_interval); | |
61 | hrtimer_init(&ctx->tmr, clockid, htmode); | |
62 | ctx->tmr.expires = texp; | |
63 | ctx->tmr.function = timerfd_tmrproc; | |
64 | if (texp.tv64 != 0) | |
65 | hrtimer_start(&ctx->tmr, texp, htmode); | |
66 | } | |
67 | ||
68 | static int timerfd_release(struct inode *inode, struct file *file) | |
69 | { | |
70 | struct timerfd_ctx *ctx = file->private_data; | |
71 | ||
72 | hrtimer_cancel(&ctx->tmr); | |
73 | kfree(ctx); | |
74 | return 0; | |
75 | } | |
76 | ||
77 | static unsigned int timerfd_poll(struct file *file, poll_table *wait) | |
78 | { | |
79 | struct timerfd_ctx *ctx = file->private_data; | |
80 | unsigned int events = 0; | |
81 | unsigned long flags; | |
82 | ||
83 | poll_wait(file, &ctx->wqh, wait); | |
84 | ||
18963c01 | 85 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
b215e283 DL |
86 | if (ctx->expired) |
87 | events |= POLLIN; | |
18963c01 | 88 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
b215e283 DL |
89 | |
90 | return events; | |
91 | } | |
92 | ||
93 | static ssize_t timerfd_read(struct file *file, char __user *buf, size_t count, | |
94 | loff_t *ppos) | |
95 | { | |
96 | struct timerfd_ctx *ctx = file->private_data; | |
97 | ssize_t res; | |
09828402 | 98 | u64 ticks = 0; |
b215e283 DL |
99 | DECLARE_WAITQUEUE(wait, current); |
100 | ||
101 | if (count < sizeof(ticks)) | |
102 | return -EINVAL; | |
18963c01 | 103 | spin_lock_irq(&ctx->wqh.lock); |
b215e283 DL |
104 | res = -EAGAIN; |
105 | if (!ctx->expired && !(file->f_flags & O_NONBLOCK)) { | |
106 | __add_wait_queue(&ctx->wqh, &wait); | |
107 | for (res = 0;;) { | |
108 | set_current_state(TASK_INTERRUPTIBLE); | |
109 | if (ctx->expired) { | |
110 | res = 0; | |
111 | break; | |
112 | } | |
113 | if (signal_pending(current)) { | |
114 | res = -ERESTARTSYS; | |
115 | break; | |
116 | } | |
18963c01 | 117 | spin_unlock_irq(&ctx->wqh.lock); |
b215e283 | 118 | schedule(); |
18963c01 | 119 | spin_lock_irq(&ctx->wqh.lock); |
b215e283 DL |
120 | } |
121 | __remove_wait_queue(&ctx->wqh, &wait); | |
122 | __set_current_state(TASK_RUNNING); | |
123 | } | |
124 | if (ctx->expired) { | |
125 | ctx->expired = 0; | |
126 | if (ctx->tintv.tv64 != 0) { | |
127 | /* | |
128 | * If tintv.tv64 != 0, this is a periodic timer that | |
129 | * needs to be re-armed. We avoid doing it in the timer | |
130 | * callback to avoid DoS attacks specifying a very | |
131 | * short timer period. | |
132 | */ | |
09828402 | 133 | ticks = (u64) |
b215e283 DL |
134 | hrtimer_forward(&ctx->tmr, |
135 | hrtimer_cb_get_time(&ctx->tmr), | |
136 | ctx->tintv); | |
137 | hrtimer_restart(&ctx->tmr); | |
138 | } else | |
139 | ticks = 1; | |
140 | } | |
18963c01 | 141 | spin_unlock_irq(&ctx->wqh.lock); |
b215e283 | 142 | if (ticks) |
09828402 | 143 | res = put_user(ticks, (u64 __user *) buf) ? -EFAULT: sizeof(ticks); |
b215e283 DL |
144 | return res; |
145 | } | |
146 | ||
147 | static const struct file_operations timerfd_fops = { | |
148 | .release = timerfd_release, | |
149 | .poll = timerfd_poll, | |
150 | .read = timerfd_read, | |
151 | }; | |
152 | ||
153 | asmlinkage long sys_timerfd(int ufd, int clockid, int flags, | |
154 | const struct itimerspec __user *utmr) | |
155 | { | |
156 | int error; | |
157 | struct timerfd_ctx *ctx; | |
158 | struct file *file; | |
159 | struct inode *inode; | |
160 | struct itimerspec ktmr; | |
161 | ||
162 | if (copy_from_user(&ktmr, utmr, sizeof(ktmr))) | |
163 | return -EFAULT; | |
164 | ||
165 | if (clockid != CLOCK_MONOTONIC && | |
166 | clockid != CLOCK_REALTIME) | |
167 | return -EINVAL; | |
168 | if (!timespec_valid(&ktmr.it_value) || | |
169 | !timespec_valid(&ktmr.it_interval)) | |
170 | return -EINVAL; | |
171 | ||
172 | if (ufd == -1) { | |
173 | ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); | |
174 | if (!ctx) | |
175 | return -ENOMEM; | |
176 | ||
177 | init_waitqueue_head(&ctx->wqh); | |
b215e283 DL |
178 | |
179 | timerfd_setup(ctx, clockid, flags, &ktmr); | |
180 | ||
181 | /* | |
182 | * When we call this, the initialization must be complete, since | |
183 | * anon_inode_getfd() will install the fd. | |
184 | */ | |
185 | error = anon_inode_getfd(&ufd, &inode, &file, "[timerfd]", | |
186 | &timerfd_fops, ctx); | |
187 | if (error) | |
188 | goto err_tmrcancel; | |
189 | } else { | |
190 | file = fget(ufd); | |
191 | if (!file) | |
192 | return -EBADF; | |
193 | ctx = file->private_data; | |
194 | if (file->f_op != &timerfd_fops) { | |
195 | fput(file); | |
196 | return -EINVAL; | |
197 | } | |
198 | /* | |
199 | * We need to stop the existing timer before reprogramming | |
200 | * it to the new values. | |
201 | */ | |
202 | for (;;) { | |
18963c01 | 203 | spin_lock_irq(&ctx->wqh.lock); |
b215e283 DL |
204 | if (hrtimer_try_to_cancel(&ctx->tmr) >= 0) |
205 | break; | |
18963c01 | 206 | spin_unlock_irq(&ctx->wqh.lock); |
b215e283 DL |
207 | cpu_relax(); |
208 | } | |
209 | /* | |
210 | * Re-program the timer to the new value ... | |
211 | */ | |
212 | timerfd_setup(ctx, clockid, flags, &ktmr); | |
213 | ||
18963c01 | 214 | spin_unlock_irq(&ctx->wqh.lock); |
b215e283 DL |
215 | fput(file); |
216 | } | |
217 | ||
218 | return ufd; | |
219 | ||
220 | err_tmrcancel: | |
221 | hrtimer_cancel(&ctx->tmr); | |
222 | kfree(ctx); | |
223 | return error; | |
224 | } | |
225 |