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/err.h>
  15 #include <linux/percpu-defs.h>
  16 #include <linux/percpu.h>
  17
  18 /*
  19  * CAREFUL: Check include/uapi/asm-generic/fcntl.h when defining
  20  * new flags, since they might collide with O_* ones. We want
  21  * to re-use O_* flags that couldn't possibly have a meaning
  22  * from eventfd, in order to leave a free define-space for
  23  * shared O_* flags.
  24  */
  25 #define EFD_SEMAPHORE (1 << 0)
  26 #define EFD_CLOEXEC O_CLOEXEC
  27 #define EFD_NONBLOCK O_NONBLOCK
  28
  29 #define EFD_SHARED_FCNTL_FLAGS (O_CLOEXEC | O_NONBLOCK)
  30 #define EFD_FLAGS_SET (EFD_SHARED_FCNTL_FLAGS | EFD_SEMAPHORE)
  31
  32 struct eventfd_ctx;
  33 struct file;
  34
  35 #ifdef CONFIG_EVENTFD
  36
  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 int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
  43                                   __u64 *cnt);
  44 void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __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
  60 static inline struct eventfd_ctx *eventfd_ctx_fdget(int fd)
  61 {
  62         return ERR_PTR(-ENOSYS);
  63 }
  64
  65 static inline int eventfd_signal(struct eventfd_ctx *ctx, int n)
  66 {
  67         return -ENOSYS;
  68 }
  69
  70 static inline void eventfd_ctx_put(struct eventfd_ctx *ctx)
  71 {
  72
  73 }
  74
  75 static inline int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx,
  76                                                 wait_queue_entry_t *wait, __u64 *cnt)
  77 {
  78         return -ENOSYS;
  79 }
  80
  81 static inline bool eventfd_signal_count(void)
  82 {
  83         return false;
  84 }
  85
  86 static inline void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
  87 {
  88
  89 }
  90
  91 #endif
  92
  93 #endif /* _LINUX_EVENTFD_H */
  94