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e1ad7468 DL |
1 | /* |
2 | * fs/eventfd.c | |
3 | * | |
4 | * Copyright (C) 2007 Davide Libenzi <davidel@xmailserver.org> | |
5 | * | |
6 | */ | |
7 | ||
8 | #include <linux/file.h> | |
9 | #include <linux/poll.h> | |
10 | #include <linux/init.h> | |
11 | #include <linux/fs.h> | |
12 | #include <linux/sched.h> | |
13 | #include <linux/kernel.h> | |
14 | #include <linux/list.h> | |
15 | #include <linux/spinlock.h> | |
16 | #include <linux/anon_inodes.h> | |
7747cdb2 | 17 | #include <linux/syscalls.h> |
5718607b | 18 | #include <linux/module.h> |
13389010 DL |
19 | #include <linux/kref.h> |
20 | #include <linux/eventfd.h> | |
e1ad7468 DL |
21 | |
22 | struct eventfd_ctx { | |
13389010 | 23 | struct kref kref; |
e1ad7468 DL |
24 | wait_queue_head_t wqh; |
25 | /* | |
26 | * Every time that a write(2) is performed on an eventfd, the | |
27 | * value of the __u64 being written is added to "count" and a | |
28 | * wakeup is performed on "wqh". A read(2) will return the "count" | |
29 | * value to userspace, and will reset "count" to zero. The kernel | |
13389010 | 30 | * side eventfd_signal() also, adds to the "count" counter and |
e1ad7468 DL |
31 | * issue a wakeup. |
32 | */ | |
33 | __u64 count; | |
bcd0b235 | 34 | unsigned int flags; |
e1ad7468 DL |
35 | }; |
36 | ||
13389010 DL |
37 | /** |
38 | * eventfd_signal - Adds @n to the eventfd counter. | |
39 | * @ctx: [in] Pointer to the eventfd context. | |
40 | * @n: [in] Value of the counter to be added to the eventfd internal counter. | |
41 | * The value cannot be negative. | |
42 | * | |
43 | * This function is supposed to be called by the kernel in paths that do not | |
44 | * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX | |
45 | * value, and we signal this as overflow condition by returining a POLLERR | |
46 | * to poll(2). | |
47 | * | |
48 | * Returns @n in case of success, a non-negative number lower than @n in case | |
49 | * of overflow, or the following error codes: | |
50 | * | |
51 | * -EINVAL : The value of @n is negative. | |
e1ad7468 | 52 | */ |
13389010 | 53 | int eventfd_signal(struct eventfd_ctx *ctx, int n) |
e1ad7468 | 54 | { |
e1ad7468 DL |
55 | unsigned long flags; |
56 | ||
57 | if (n < 0) | |
58 | return -EINVAL; | |
d48eb233 | 59 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
e1ad7468 DL |
60 | if (ULLONG_MAX - ctx->count < n) |
61 | n = (int) (ULLONG_MAX - ctx->count); | |
62 | ctx->count += n; | |
63 | if (waitqueue_active(&ctx->wqh)) | |
39510888 | 64 | wake_up_locked_poll(&ctx->wqh, POLLIN); |
d48eb233 | 65 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
e1ad7468 DL |
66 | |
67 | return n; | |
68 | } | |
5718607b | 69 | EXPORT_SYMBOL_GPL(eventfd_signal); |
e1ad7468 | 70 | |
13389010 DL |
71 | static void eventfd_free(struct kref *kref) |
72 | { | |
73 | struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref); | |
74 | ||
75 | kfree(ctx); | |
76 | } | |
77 | ||
78 | /** | |
79 | * eventfd_ctx_get - Acquires a reference to the internal eventfd context. | |
80 | * @ctx: [in] Pointer to the eventfd context. | |
81 | * | |
82 | * Returns: In case of success, returns a pointer to the eventfd context. | |
83 | */ | |
84 | struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx) | |
85 | { | |
86 | kref_get(&ctx->kref); | |
87 | return ctx; | |
88 | } | |
89 | EXPORT_SYMBOL_GPL(eventfd_ctx_get); | |
90 | ||
91 | /** | |
92 | * eventfd_ctx_put - Releases a reference to the internal eventfd context. | |
93 | * @ctx: [in] Pointer to eventfd context. | |
94 | * | |
95 | * The eventfd context reference must have been previously acquired either | |
96 | * with eventfd_ctx_get() or eventfd_ctx_fdget()). | |
97 | */ | |
98 | void eventfd_ctx_put(struct eventfd_ctx *ctx) | |
99 | { | |
100 | kref_put(&ctx->kref, eventfd_free); | |
101 | } | |
102 | EXPORT_SYMBOL_GPL(eventfd_ctx_put); | |
103 | ||
e1ad7468 DL |
104 | static int eventfd_release(struct inode *inode, struct file *file) |
105 | { | |
13389010 DL |
106 | struct eventfd_ctx *ctx = file->private_data; |
107 | ||
108 | wake_up_poll(&ctx->wqh, POLLHUP); | |
109 | eventfd_ctx_put(ctx); | |
e1ad7468 DL |
110 | return 0; |
111 | } | |
112 | ||
113 | static unsigned int eventfd_poll(struct file *file, poll_table *wait) | |
114 | { | |
115 | struct eventfd_ctx *ctx = file->private_data; | |
116 | unsigned int events = 0; | |
117 | unsigned long flags; | |
118 | ||
119 | poll_wait(file, &ctx->wqh, wait); | |
120 | ||
d48eb233 | 121 | spin_lock_irqsave(&ctx->wqh.lock, flags); |
e1ad7468 DL |
122 | if (ctx->count > 0) |
123 | events |= POLLIN; | |
124 | if (ctx->count == ULLONG_MAX) | |
125 | events |= POLLERR; | |
126 | if (ULLONG_MAX - 1 > ctx->count) | |
127 | events |= POLLOUT; | |
d48eb233 | 128 | spin_unlock_irqrestore(&ctx->wqh.lock, flags); |
e1ad7468 DL |
129 | |
130 | return events; | |
131 | } | |
132 | ||
133 | static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count, | |
134 | loff_t *ppos) | |
135 | { | |
136 | struct eventfd_ctx *ctx = file->private_data; | |
137 | ssize_t res; | |
bcd0b235 | 138 | __u64 ucnt = 0; |
e1ad7468 DL |
139 | DECLARE_WAITQUEUE(wait, current); |
140 | ||
141 | if (count < sizeof(ucnt)) | |
142 | return -EINVAL; | |
d48eb233 | 143 | spin_lock_irq(&ctx->wqh.lock); |
e1ad7468 | 144 | res = -EAGAIN; |
bcd0b235 | 145 | if (ctx->count > 0) |
e1ad7468 DL |
146 | res = sizeof(ucnt); |
147 | else if (!(file->f_flags & O_NONBLOCK)) { | |
148 | __add_wait_queue(&ctx->wqh, &wait); | |
149 | for (res = 0;;) { | |
150 | set_current_state(TASK_INTERRUPTIBLE); | |
151 | if (ctx->count > 0) { | |
e1ad7468 DL |
152 | res = sizeof(ucnt); |
153 | break; | |
154 | } | |
155 | if (signal_pending(current)) { | |
156 | res = -ERESTARTSYS; | |
157 | break; | |
158 | } | |
d48eb233 | 159 | spin_unlock_irq(&ctx->wqh.lock); |
e1ad7468 | 160 | schedule(); |
d48eb233 | 161 | spin_lock_irq(&ctx->wqh.lock); |
e1ad7468 DL |
162 | } |
163 | __remove_wait_queue(&ctx->wqh, &wait); | |
164 | __set_current_state(TASK_RUNNING); | |
165 | } | |
bcd0b235 DL |
166 | if (likely(res > 0)) { |
167 | ucnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count; | |
168 | ctx->count -= ucnt; | |
e1ad7468 | 169 | if (waitqueue_active(&ctx->wqh)) |
39510888 | 170 | wake_up_locked_poll(&ctx->wqh, POLLOUT); |
e1ad7468 | 171 | } |
d48eb233 | 172 | spin_unlock_irq(&ctx->wqh.lock); |
e1ad7468 DL |
173 | if (res > 0 && put_user(ucnt, (__u64 __user *) buf)) |
174 | return -EFAULT; | |
175 | ||
176 | return res; | |
177 | } | |
178 | ||
179 | static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count, | |
180 | loff_t *ppos) | |
181 | { | |
182 | struct eventfd_ctx *ctx = file->private_data; | |
183 | ssize_t res; | |
184 | __u64 ucnt; | |
185 | DECLARE_WAITQUEUE(wait, current); | |
186 | ||
187 | if (count < sizeof(ucnt)) | |
188 | return -EINVAL; | |
189 | if (copy_from_user(&ucnt, buf, sizeof(ucnt))) | |
190 | return -EFAULT; | |
191 | if (ucnt == ULLONG_MAX) | |
192 | return -EINVAL; | |
d48eb233 | 193 | spin_lock_irq(&ctx->wqh.lock); |
e1ad7468 DL |
194 | res = -EAGAIN; |
195 | if (ULLONG_MAX - ctx->count > ucnt) | |
196 | res = sizeof(ucnt); | |
197 | else if (!(file->f_flags & O_NONBLOCK)) { | |
198 | __add_wait_queue(&ctx->wqh, &wait); | |
199 | for (res = 0;;) { | |
200 | set_current_state(TASK_INTERRUPTIBLE); | |
201 | if (ULLONG_MAX - ctx->count > ucnt) { | |
202 | res = sizeof(ucnt); | |
203 | break; | |
204 | } | |
205 | if (signal_pending(current)) { | |
206 | res = -ERESTARTSYS; | |
207 | break; | |
208 | } | |
d48eb233 | 209 | spin_unlock_irq(&ctx->wqh.lock); |
e1ad7468 | 210 | schedule(); |
d48eb233 | 211 | spin_lock_irq(&ctx->wqh.lock); |
e1ad7468 DL |
212 | } |
213 | __remove_wait_queue(&ctx->wqh, &wait); | |
214 | __set_current_state(TASK_RUNNING); | |
215 | } | |
bcd0b235 | 216 | if (likely(res > 0)) { |
e1ad7468 DL |
217 | ctx->count += ucnt; |
218 | if (waitqueue_active(&ctx->wqh)) | |
39510888 | 219 | wake_up_locked_poll(&ctx->wqh, POLLIN); |
e1ad7468 | 220 | } |
d48eb233 | 221 | spin_unlock_irq(&ctx->wqh.lock); |
e1ad7468 DL |
222 | |
223 | return res; | |
224 | } | |
225 | ||
226 | static const struct file_operations eventfd_fops = { | |
227 | .release = eventfd_release, | |
228 | .poll = eventfd_poll, | |
229 | .read = eventfd_read, | |
230 | .write = eventfd_write, | |
231 | }; | |
232 | ||
13389010 DL |
233 | /** |
234 | * eventfd_fget - Acquire a reference of an eventfd file descriptor. | |
235 | * @fd: [in] Eventfd file descriptor. | |
236 | * | |
237 | * Returns a pointer to the eventfd file structure in case of success, or the | |
238 | * following error pointer: | |
239 | * | |
240 | * -EBADF : Invalid @fd file descriptor. | |
241 | * -EINVAL : The @fd file descriptor is not an eventfd file. | |
242 | */ | |
e1ad7468 DL |
243 | struct file *eventfd_fget(int fd) |
244 | { | |
245 | struct file *file; | |
246 | ||
247 | file = fget(fd); | |
248 | if (!file) | |
249 | return ERR_PTR(-EBADF); | |
250 | if (file->f_op != &eventfd_fops) { | |
251 | fput(file); | |
252 | return ERR_PTR(-EINVAL); | |
253 | } | |
254 | ||
255 | return file; | |
256 | } | |
5718607b | 257 | EXPORT_SYMBOL_GPL(eventfd_fget); |
e1ad7468 | 258 | |
13389010 DL |
259 | /** |
260 | * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context. | |
261 | * @fd: [in] Eventfd file descriptor. | |
262 | * | |
263 | * Returns a pointer to the internal eventfd context, otherwise the error | |
264 | * pointers returned by the following functions: | |
265 | * | |
266 | * eventfd_fget | |
267 | */ | |
268 | struct eventfd_ctx *eventfd_ctx_fdget(int fd) | |
269 | { | |
270 | struct file *file; | |
271 | struct eventfd_ctx *ctx; | |
272 | ||
273 | file = eventfd_fget(fd); | |
274 | if (IS_ERR(file)) | |
275 | return (struct eventfd_ctx *) file; | |
276 | ctx = eventfd_ctx_get(file->private_data); | |
277 | fput(file); | |
278 | ||
279 | return ctx; | |
280 | } | |
281 | EXPORT_SYMBOL_GPL(eventfd_ctx_fdget); | |
282 | ||
283 | /** | |
284 | * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context. | |
285 | * @file: [in] Eventfd file pointer. | |
286 | * | |
287 | * Returns a pointer to the internal eventfd context, otherwise the error | |
288 | * pointer: | |
289 | * | |
290 | * -EINVAL : The @fd file descriptor is not an eventfd file. | |
291 | */ | |
292 | struct eventfd_ctx *eventfd_ctx_fileget(struct file *file) | |
293 | { | |
294 | if (file->f_op != &eventfd_fops) | |
295 | return ERR_PTR(-EINVAL); | |
296 | ||
297 | return eventfd_ctx_get(file->private_data); | |
298 | } | |
299 | EXPORT_SYMBOL_GPL(eventfd_ctx_fileget); | |
300 | ||
d4e82042 | 301 | SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags) |
e1ad7468 | 302 | { |
2030a42c | 303 | int fd; |
e1ad7468 | 304 | struct eventfd_ctx *ctx; |
e1ad7468 | 305 | |
e38b36f3 UD |
306 | /* Check the EFD_* constants for consistency. */ |
307 | BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC); | |
308 | BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK); | |
309 | ||
bcd0b235 | 310 | if (flags & ~EFD_FLAGS_SET) |
b087498e UD |
311 | return -EINVAL; |
312 | ||
e1ad7468 DL |
313 | ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); |
314 | if (!ctx) | |
315 | return -ENOMEM; | |
316 | ||
13389010 | 317 | kref_init(&ctx->kref); |
e1ad7468 | 318 | init_waitqueue_head(&ctx->wqh); |
e1ad7468 | 319 | ctx->count = count; |
bcd0b235 | 320 | ctx->flags = flags; |
e1ad7468 DL |
321 | |
322 | /* | |
323 | * When we call this, the initialization must be complete, since | |
324 | * anon_inode_getfd() will install the fd. | |
325 | */ | |
b087498e | 326 | fd = anon_inode_getfd("[eventfd]", &eventfd_fops, ctx, |
bcd0b235 | 327 | flags & EFD_SHARED_FCNTL_FLAGS); |
2030a42c AV |
328 | if (fd < 0) |
329 | kfree(ctx); | |
330 | return fd; | |
e1ad7468 DL |
331 | } |
332 | ||
d4e82042 | 333 | SYSCALL_DEFINE1(eventfd, unsigned int, count) |
b087498e UD |
334 | { |
335 | return sys_eventfd2(count, 0); | |
336 | } | |
bcd0b235 | 337 |