include/linux/eventfd.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 /*
   3  *  include/linux/eventfd.h
   4  *
   5  *  Copyright (C) 2007  Davide Libenzi <davidel@xmailserver.org>
   6  *
   7  */
   8
   9 #ifndef _LINUX_EVENTFD_H
  10 #define _LINUX_EVENTFD_H
  11
  12 #include <linux/fcntl.h>
  13 #include <linux/wait.h>
  14 #include <linux/percpu-defs.h>
  15 #include <linux/percpu.h>
  16
  17 /*
  18  * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
  19  * new flags, since they might collide with O_* ones. We want
  20  * to re-use O_* flags that couldn't possibly have a meaning
  21  * from eventfd, in order to leave a free define-space for
  22  * shared O_* flags.
  23  */
  24 #define EFD_SEMAPHORE (1 << 0)
  25 #define EFD_CLOEXEC O_CLOEXEC
  26 #define EFD_NONBLOCK O_NONBLOCK
  27
  28 #define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
  29 #define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE)
  30
  31 struct file;
  32
  33 #ifdef CONFIG_EVENTFD
  34
  35 struct file *eventfd_file_create(unsigned int count, int flags);
  36 struct eventfd_ctx *eventfd_ctx_get(struct eventfd_ctx *ctx);
  37 void eventfd_ctx_put(struct eventfd_ctx *ctx);
  38 struct file *eventfd_fget(int fd);
  39 struct eventfd_ctx *eventfd_ctx_fdget(int fd);
  40 struct eventfd_ctx *eventfd_ctx_fileget(struct file *file);
  41 __u64 eventfd_signal(struct eventfd_ctx *ctx, __u64 n);
  42 ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait, __u64 *cnt);
  43 int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
  44                                   __u64 *cnt);
  45
  46 DECLARE_PER_CPU(int, eventfd_wake_count);
  47
  48 static inline bool eventfd_signal_count(void)
  49 {
  50         return this_cpu_read(eventfd_wake_count);
  51 }
  52
  53 #else /* CONFIG_EVENTFD */
  54
  55 /*
  56  * Ugly ugly ugly error layer to support modules that uses eventfd but
  57  * pretend to work in !CONFIG_EVENTFD configurations. Namely, AIO.
  58  */
  59 static inline struct file *eventfd_file_create(unsigned int count, int flags)
  60 {
  61         return ERR_PTR(-ENOSYS);
  62 }
  63
  64 static inline struct eventfd_ctx *eventfd_ctx_fdget(int fd)
  65 {
  66         return ERR_PTR(-ENOSYS);
  67 }
  68
  69 static inline int eventfd_signal(struct eventfd_ctx *ctx, int n)
  70 {
  71         return -ENOSYS;
  72 }
  73
  74 static inline void eventfd_ctx_put(struct eventfd_ctx *ctx)
  75 {
  76
  77 }
  78
  79 static inline ssize_t eventfd_ctx_read(struct eventfd_ctx *ctx, int no_wait,
  80                                        __u64 *cnt)
  81 {
  82         return -ENOSYS;
  83 }
  84
  85 static inline int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx,
  86                                                 wait_queue_entry_t *wait, __u64 *cnt)
  87 {
  88         return -ENOSYS;
  89 }
  90
  91 static inline bool eventfd_signal_count(void)
  92 {
  93         return false;
  94 }
  95
  96 #endif
  97
  98 #endif /* _LINUX_EVENTFD_H */
  99