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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/slab.h>
15#include <linux/list.h>
16#include <linux/spinlock.h>
17#include <linux/anon_inodes.h>
18#include <linux/syscalls.h>
19#include <linux/module.h>
20#include <linux/kref.h>
21#include <linux/eventfd.h>
22
23struct eventfd_ctx {
24 struct kref kref;
25 wait_queue_head_t wqh;
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34 __u64 count;
35 unsigned int flags;
36};
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53
54int eventfd_signal(struct eventfd_ctx *ctx, int n)
55{
56 unsigned long flags;
57
58 if (n < 0)
59 return -EINVAL;
60 spin_lock_irqsave(&ctx->wqh.lock, flags);
61 if (ULLONG_MAX - ctx->count < n)
62 n = (int) (ULLONG_MAX - ctx->count);
63 ctx->count += n;
64 if (waitqueue_active(&ctx->wqh))
65 wake_up_locked_poll(&ctx->wqh, POLLIN);
66 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
67
68 return n;
69}
70EXPORT_SYMBOL_GPL(eventfd_signal);
71
72static void eventfd_free_ctx(struct eventfd_ctx *ctx)
73{
74 kfree(ctx);
75}
76
77static void eventfd_free(struct kref *kref)
78{
79 struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
80
81 eventfd_free_ctx(ctx);
82}
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90struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx)
91{
92 kref_get(&ctx->kref);
93 return ctx;
94}
95EXPORT_SYMBOL_GPL(eventfd_ctx_get);
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104void eventfd_ctx_put(struct eventfd_ctx *ctx)
105{
106 kref_put(&ctx->kref, eventfd_free);
107}
108EXPORT_SYMBOL_GPL(eventfd_ctx_put);
109
110static int eventfd_release(struct inode *inode, struct file *file)
111{
112 struct eventfd_ctx *ctx = file->private_data;
113
114 wake_up_poll(&ctx->wqh, POLLHUP);
115 eventfd_ctx_put(ctx);
116 return 0;
117}
118
119static unsigned int eventfd_poll(struct file *file, poll_table *wait)
120{
121 struct eventfd_ctx *ctx = file->private_data;
122 unsigned int events = 0;
123 unsigned long flags;
124
125 poll_wait(file, &ctx->wqh, wait);
126
127 spin_lock_irqsave(&ctx->wqh.lock, flags);
128 if (ctx->count > 0)
129 events |= POLLIN;
130 if (ctx->count == ULLONG_MAX)
131 events |= POLLERR;
132 if (ULLONG_MAX - 1 > ctx->count)
133 events |= POLLOUT;
134 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
135
136 return events;
137}
138
139static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
140{
141 *cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
142 ctx->count -= *cnt;
143}
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158int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_t *wait,
159 __u64 *cnt)
160{
161 unsigned long flags;
162
163 spin_lock_irqsave(&ctx->wqh.lock, flags);
164 eventfd_ctx_do_read(ctx, cnt);
165 __remove_wait_queue(&ctx->wqh, wait);
166 if (*cnt != 0 && waitqueue_active(&ctx->wqh))
167 wake_up_locked_poll(&ctx->wqh, POLLOUT);
168 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
169
170 return *cnt != 0 ? 0 : -EAGAIN;
171}
172EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
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188ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait, __u64 *cnt)
189{
190 ssize_t res;
191 DECLARE_WAITQUEUE(wait, current);
192
193 spin_lock_irq(&ctx->wqh.lock);
194 *cnt = 0;
195 res = -EAGAIN;
196 if (ctx->count > 0)
197 res = 0;
198 else if (!no_wait) {
199 __add_wait_queue(&ctx->wqh, &wait);
200 for (;;) {
201 set_current_state(TASK_INTERRUPTIBLE);
202 if (ctx->count > 0) {
203 res = 0;
204 break;
205 }
206 if (signal_pending(current)) {
207 res = -ERESTARTSYS;
208 break;
209 }
210 spin_unlock_irq(&ctx->wqh.lock);
211 schedule();
212 spin_lock_irq(&ctx->wqh.lock);
213 }
214 __remove_wait_queue(&ctx->wqh, &wait);
215 __set_current_state(TASK_RUNNING);
216 }
217 if (likely(res == 0)) {
218 eventfd_ctx_do_read(ctx, cnt);
219 if (waitqueue_active(&ctx->wqh))
220 wake_up_locked_poll(&ctx->wqh, POLLOUT);
221 }
222 spin_unlock_irq(&ctx->wqh.lock);
223
224 return res;
225}
226EXPORT_SYMBOL_GPL(eventfd_ctx_read);
227
228static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
229 loff_t *ppos)
230{
231 struct eventfd_ctx *ctx = file->private_data;
232 ssize_t res;
233 __u64 cnt;
234
235 if (count < sizeof(cnt))
236 return -EINVAL;
237 res = eventfd_ctx_read(ctx, file->f_flags & O_NONBLOCK, &cnt);
238 if (res < 0)
239 return res;
240
241 return put_user(cnt, (__u64 __user *) buf) ? -EFAULT : sizeof(cnt);
242}
243
244static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
245 loff_t *ppos)
246{
247 struct eventfd_ctx *ctx = file->private_data;
248 ssize_t res;
249 __u64 ucnt;
250 DECLARE_WAITQUEUE(wait, current);
251
252 if (count < sizeof(ucnt))
253 return -EINVAL;
254 if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
255 return -EFAULT;
256 if (ucnt == ULLONG_MAX)
257 return -EINVAL;
258 spin_lock_irq(&ctx->wqh.lock);
259 res = -EAGAIN;
260 if (ULLONG_MAX - ctx->count > ucnt)
261 res = sizeof(ucnt);
262 else if (!(file->f_flags & O_NONBLOCK)) {
263 __add_wait_queue(&ctx->wqh, &wait);
264 for (res = 0;;) {
265 set_current_state(TASK_INTERRUPTIBLE);
266 if (ULLONG_MAX - ctx->count > ucnt) {
267 res = sizeof(ucnt);
268 break;
269 }
270 if (signal_pending(current)) {
271 res = -ERESTARTSYS;
272 break;
273 }
274 spin_unlock_irq(&ctx->wqh.lock);
275 schedule();
276 spin_lock_irq(&ctx->wqh.lock);
277 }
278 __remove_wait_queue(&ctx->wqh, &wait);
279 __set_current_state(TASK_RUNNING);
280 }
281 if (likely(res > 0)) {
282 ctx->count += ucnt;
283 if (waitqueue_active(&ctx->wqh))
284 wake_up_locked_poll(&ctx->wqh, POLLIN);
285 }
286 spin_unlock_irq(&ctx->wqh.lock);
287
288 return res;
289}
290
291static const struct file_operations eventfd_fops = {
292 .release = eventfd_release,
293 .poll = eventfd_poll,
294 .read = eventfd_read,
295 .write = eventfd_write,
296 .llseek = noop_llseek,
297};
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309struct file *eventfd_fget(int fd)
310{
311 struct file *file;
312
313 file = fget(fd);
314 if (!file)
315 return ERR_PTR(-EBADF);
316 if (file->f_op != &eventfd_fops) {
317 fput(file);
318 return ERR_PTR(-EINVAL);
319 }
320
321 return file;
322}
323EXPORT_SYMBOL_GPL(eventfd_fget);
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334struct eventfd_ctx *eventfd_ctx_fdget(int fd)
335{
336 struct file *file;
337 struct eventfd_ctx *ctx;
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339 file = eventfd_fget(fd);
340 if (IS_ERR(file))
341 return (struct eventfd_ctx *) file;
342 ctx = eventfd_ctx_get(file->private_data);
343 fput(file);
344
345 return ctx;
346}
347EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
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358struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
359{
360 if (file->f_op != &eventfd_fops)
361 return ERR_PTR(-EINVAL);
362
363 return eventfd_ctx_get(file->private_data);
364}
365EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
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381struct file *eventfd_file_create(unsigned int count, int flags)
382{
383 struct file *file;
384 struct eventfd_ctx *ctx;
385
386
387 BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
388 BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
389
390 if (flags & ~EFD_FLAGS_SET)
391 return ERR_PTR(-EINVAL);
392
393 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
394 if (!ctx)
395 return ERR_PTR(-ENOMEM);
396
397 kref_init(&ctx->kref);
398 init_waitqueue_head(&ctx->wqh);
399 ctx->count = count;
400 ctx->flags = flags;
401
402 file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
403 O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
404 if (IS_ERR(file))
405 eventfd_free_ctx(ctx);
406
407 return file;
408}
409
410SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
411{
412 int fd, error;
413 struct file *file;
414
415 error = get_unused_fd_flags(flags & EFD_SHARED_FCNTL_FLAGS);
416 if (error < 0)
417 return error;
418 fd = error;
419
420 file = eventfd_file_create(count, flags);
421 if (IS_ERR(file)) {
422 error = PTR_ERR(file);
423 goto err_put_unused_fd;
424 }
425 fd_install(fd, file);
426
427 return fd;
428
429err_put_unused_fd:
430 put_unused_fd(fd);
431
432 return error;
433}
434
435SYSCALL_DEFINE1(eventfd, unsigned int, count)
436{
437 return sys_eventfd2(count, 0);
438}
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440