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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/export.h>
20#include <linux/kref.h>
21#include <linux/eventfd.h>
22#include <linux/proc_fs.h>
23#include <linux/seq_file.h>
24
25struct eventfd_ctx {
26 struct kref kref;
27 wait_queue_head_t wqh;
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36 __u64 count;
37 unsigned int flags;
38};
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53
54__u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n)
55{
56 unsigned long flags;
57
58 spin_lock_irqsave(&ctx->wqh.lock, flags);
59 if (ULLONG_MAX - ctx->count < n)
60 n = ULLONG_MAX - ctx->count;
61 ctx->count += n;
62 if (waitqueue_active(&ctx->wqh))
63 wake_up_locked_poll(&ctx->wqh, POLLIN);
64 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
65
66 return n;
67}
68EXPORT_SYMBOL_GPL(eventfd_signal);
69
70static void eventfd_free_ctx(struct eventfd_ctx *ctx)
71{
72 kfree(ctx);
73}
74
75static void eventfd_free(struct kref *kref)
76{
77 struct eventfd_ctx *ctx = container_of(kref, struct eventfd_ctx, kref);
78
79 eventfd_free_ctx(ctx);
80}
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88struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx)
89{
90 kref_get(&ctx->kref);
91 return ctx;
92}
93EXPORT_SYMBOL_GPL(eventfd_ctx_get);
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101
102void eventfd_ctx_put(struct eventfd_ctx *ctx)
103{
104 kref_put(&ctx->kref, eventfd_free);
105}
106EXPORT_SYMBOL_GPL(eventfd_ctx_put);
107
108static int eventfd_release(struct inode *inode, struct file *file)
109{
110 struct eventfd_ctx *ctx = file->private_data;
111
112 wake_up_poll(&ctx->wqh, POLLHUP);
113 eventfd_ctx_put(ctx);
114 return 0;
115}
116
117static unsigned int eventfd_poll(struct file *file, poll_table *wait)
118{
119 struct eventfd_ctx *ctx = file->private_data;
120 unsigned int events = 0;
121 unsigned long flags;
122
123 poll_wait(file, &ctx->wqh, wait);
124
125 spin_lock_irqsave(&ctx->wqh.lock, flags);
126 if (ctx->count > 0)
127 events |= POLLIN;
128 if (ctx->count == ULLONG_MAX)
129 events |= POLLERR;
130 if (ULLONG_MAX - 1 > ctx->count)
131 events |= POLLOUT;
132 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
133
134 return events;
135}
136
137static void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
138{
139 *cnt = (ctx->flags & EFD_SEMAPHORE) ? 1 : ctx->count;
140 ctx->count -= *cnt;
141}
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156int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_t *wait,
157 __u64 *cnt)
158{
159 unsigned long flags;
160
161 spin_lock_irqsave(&ctx->wqh.lock, flags);
162 eventfd_ctx_do_read(ctx, cnt);
163 __remove_wait_queue(&ctx->wqh, wait);
164 if (*cnt != 0 && waitqueue_active(&ctx->wqh))
165 wake_up_locked_poll(&ctx->wqh, POLLOUT);
166 spin_unlock_irqrestore(&ctx->wqh.lock, flags);
167
168 return *cnt != 0 ? 0 : -EAGAIN;
169}
170EXPORT_SYMBOL_GPL(eventfd_ctx_remove_wait_queue);
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185
186ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait, __u64 *cnt)
187{
188 ssize_t res;
189 DECLARE_WAITQUEUE(wait, current);
190
191 spin_lock_irq(&ctx->wqh.lock);
192 *cnt = 0;
193 res = -EAGAIN;
194 if (ctx->count > 0)
195 res = 0;
196 else if (!no_wait) {
197 __add_wait_queue(&ctx->wqh, &wait);
198 for (;;) {
199 set_current_state(TASK_INTERRUPTIBLE);
200 if (ctx->count > 0) {
201 res = 0;
202 break;
203 }
204 if (signal_pending(current)) {
205 res = -ERESTARTSYS;
206 break;
207 }
208 spin_unlock_irq(&ctx->wqh.lock);
209 schedule();
210 spin_lock_irq(&ctx->wqh.lock);
211 }
212 __remove_wait_queue(&ctx->wqh, &wait);
213 __set_current_state(TASK_RUNNING);
214 }
215 if (likely(res == 0)) {
216 eventfd_ctx_do_read(ctx, cnt);
217 if (waitqueue_active(&ctx->wqh))
218 wake_up_locked_poll(&ctx->wqh, POLLOUT);
219 }
220 spin_unlock_irq(&ctx->wqh.lock);
221
222 return res;
223}
224EXPORT_SYMBOL_GPL(eventfd_ctx_read);
225
226static ssize_t eventfd_read(struct file *file, char __user *buf, size_t count,
227 loff_t *ppos)
228{
229 struct eventfd_ctx *ctx = file->private_data;
230 ssize_t res;
231 __u64 cnt;
232
233 if (count < sizeof(cnt))
234 return -EINVAL;
235 res = eventfd_ctx_read(ctx, file->f_flags & O_NONBLOCK, &cnt);
236 if (res < 0)
237 return res;
238
239 return put_user(cnt, (__u64 __user *) buf) ? -EFAULT : sizeof(cnt);
240}
241
242static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
243 loff_t *ppos)
244{
245 struct eventfd_ctx *ctx = file->private_data;
246 ssize_t res;
247 __u64 ucnt;
248 DECLARE_WAITQUEUE(wait, current);
249
250 if (count < sizeof(ucnt))
251 return -EINVAL;
252 if (copy_from_user(&ucnt, buf, sizeof(ucnt)))
253 return -EFAULT;
254 if (ucnt == ULLONG_MAX)
255 return -EINVAL;
256 spin_lock_irq(&ctx->wqh.lock);
257 res = -EAGAIN;
258 if (ULLONG_MAX - ctx->count > ucnt)
259 res = sizeof(ucnt);
260 else if (!(file->f_flags & O_NONBLOCK)) {
261 __add_wait_queue(&ctx->wqh, &wait);
262 for (res = 0;;) {
263 set_current_state(TASK_INTERRUPTIBLE);
264 if (ULLONG_MAX - ctx->count > ucnt) {
265 res = sizeof(ucnt);
266 break;
267 }
268 if (signal_pending(current)) {
269 res = -ERESTARTSYS;
270 break;
271 }
272 spin_unlock_irq(&ctx->wqh.lock);
273 schedule();
274 spin_lock_irq(&ctx->wqh.lock);
275 }
276 __remove_wait_queue(&ctx->wqh, &wait);
277 __set_current_state(TASK_RUNNING);
278 }
279 if (likely(res > 0)) {
280 ctx->count += ucnt;
281 if (waitqueue_active(&ctx->wqh))
282 wake_up_locked_poll(&ctx->wqh, POLLIN);
283 }
284 spin_unlock_irq(&ctx->wqh.lock);
285
286 return res;
287}
288
289#ifdef CONFIG_PROC_FS
290static int eventfd_show_fdinfo(struct seq_file *m, struct file *f)
291{
292 struct eventfd_ctx *ctx = f->private_data;
293 int ret;
294
295 spin_lock_irq(&ctx->wqh.lock);
296 ret = seq_printf(m, "eventfd-count: %16llx\n",
297 (unsigned long long)ctx->count);
298 spin_unlock_irq(&ctx->wqh.lock);
299
300 return ret;
301}
302#endif
303
304static const struct file_operations eventfd_fops = {
305#ifdef CONFIG_PROC_FS
306 .show_fdinfo = eventfd_show_fdinfo,
307#endif
308 .release = eventfd_release,
309 .poll = eventfd_poll,
310 .read = eventfd_read,
311 .write = eventfd_write,
312 .llseek = noop_llseek,
313};
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325struct file *eventfd_fget(int fd)
326{
327 struct file *file;
328
329 file = fget(fd);
330 if (!file)
331 return ERR_PTR(-EBADF);
332 if (file->f_op != &eventfd_fops) {
333 fput(file);
334 return ERR_PTR(-EINVAL);
335 }
336
337 return file;
338}
339EXPORT_SYMBOL_GPL(eventfd_fget);
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350struct eventfd_ctx *eventfd_ctx_fdget(int fd)
351{
352 struct file *file;
353 struct eventfd_ctx *ctx;
354
355 file = eventfd_fget(fd);
356 if (IS_ERR(file))
357 return (struct eventfd_ctx *) file;
358 ctx = eventfd_ctx_get(file->private_data);
359 fput(file);
360
361 return ctx;
362}
363EXPORT_SYMBOL_GPL(eventfd_ctx_fdget);
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374struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
375{
376 if (file->f_op != &eventfd_fops)
377 return ERR_PTR(-EINVAL);
378
379 return eventfd_ctx_get(file->private_data);
380}
381EXPORT_SYMBOL_GPL(eventfd_ctx_fileget);
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397struct file *eventfd_file_create(unsigned int count, int flags)
398{
399 struct file *file;
400 struct eventfd_ctx *ctx;
401
402
403 BUILD_BUG_ON(EFD_CLOEXEC != O_CLOEXEC);
404 BUILD_BUG_ON(EFD_NONBLOCK != O_NONBLOCK);
405
406 if (flags & ~EFD_FLAGS_SET)
407 return ERR_PTR(-EINVAL);
408
409 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
410 if (!ctx)
411 return ERR_PTR(-ENOMEM);
412
413 kref_init(&ctx->kref);
414 init_waitqueue_head(&ctx->wqh);
415 ctx->count = count;
416 ctx->flags = flags;
417
418 file = anon_inode_getfile("[eventfd]", &eventfd_fops, ctx,
419 O_RDWR | (flags & EFD_SHARED_FCNTL_FLAGS));
420 if (IS_ERR(file))
421 eventfd_free_ctx(ctx);
422
423 return file;
424}
425
426SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
427{
428 int fd, error;
429 struct file *file;
430
431 error = get_unused_fd_flags(flags & EFD_SHARED_FCNTL_FLAGS);
432 if (error < 0)
433 return error;
434 fd = error;
435
436 file = eventfd_file_create(count, flags);
437 if (IS_ERR(file)) {
438 error = PTR_ERR(file);
439 goto err_put_unused_fd;
440 }
441 fd_install(fd, file);
442
443 return fd;
444
445err_put_unused_fd:
446 put_unused_fd(fd);
447
448 return error;
449}
450
451SYSCALL_DEFINE1(eventfd, unsigned int, count)
452{
453 return sys_eventfd2(count, 0);
454}
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