linux/fs/eventfd.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 *  fs/eventfd.c
 *
 *  Copyright (C) 2007  Davide Libenzi <[email protected]>
 *
 */

#include <linux/file.h>
#include <linux/poll.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/sched/signal.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/anon_inodes.h>
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/kref.h>
#include <linux/eventfd.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/idr.h>
#include <linux/uio.h>

static DEFINE_IDA(eventfd_ida);

struct eventfd_ctx { … };

/**
 * eventfd_signal_mask - Increment the event counter
 * @ctx: [in] Pointer to the eventfd context.
 * @mask: [in] poll mask
 *
 * This function is supposed to be called by the kernel in paths that do not
 * allow sleeping. In this function we allow the counter to reach the ULLONG_MAX
 * value, and we signal this as overflow condition by returning a EPOLLERR
 * to poll(2).
 */
void eventfd_signal_mask(struct eventfd_ctx *ctx, __poll_t mask)
{ … }
EXPORT_SYMBOL_GPL(…);

static void eventfd_free_ctx(struct eventfd_ctx *ctx)
{ … }

static void eventfd_free(struct kref *kref)
{ … }

/**
 * eventfd_ctx_put - Releases a reference to the internal eventfd context.
 * @ctx: [in] Pointer to eventfd context.
 *
 * The eventfd context reference must have been previously acquired either
 * with eventfd_ctx_fdget() or eventfd_ctx_fileget().
 */
void eventfd_ctx_put(struct eventfd_ctx *ctx)
{ … }
EXPORT_SYMBOL_GPL(…);

static int eventfd_release(struct inode *inode, struct file *file)
{ … }

static __poll_t eventfd_poll(struct file *file, poll_table *wait)
{ … }

void eventfd_ctx_do_read(struct eventfd_ctx *ctx, __u64 *cnt)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * eventfd_ctx_remove_wait_queue - Read the current counter and removes wait queue.
 * @ctx: [in] Pointer to eventfd context.
 * @wait: [in] Wait queue to be removed.
 * @cnt: [out] Pointer to the 64-bit counter value.
 *
 * Returns %0 if successful, or the following error codes:
 *
 * -EAGAIN      : The operation would have blocked.
 *
 * This is used to atomically remove a wait queue entry from the eventfd wait
 * queue head, and read/reset the counter value.
 */
int eventfd_ctx_remove_wait_queue(struct eventfd_ctx *ctx, wait_queue_entry_t *wait,
				  __u64 *cnt)
{ … }
EXPORT_SYMBOL_GPL(…);

static ssize_t eventfd_read(struct kiocb *iocb, struct iov_iter *to)
{ … }

static ssize_t eventfd_write(struct file *file, const char __user *buf, size_t count,
			     loff_t *ppos)
{ … }

#ifdef CONFIG_PROC_FS
static void eventfd_show_fdinfo(struct seq_file *m, struct file *f)
{ … }
#endif

static const struct file_operations eventfd_fops = …;

/**
 * eventfd_fget - Acquire a reference of an eventfd file descriptor.
 * @fd: [in] Eventfd file descriptor.
 *
 * Returns a pointer to the eventfd file structure in case of success, or the
 * following error pointer:
 *
 * -EBADF    : Invalid @fd file descriptor.
 * -EINVAL   : The @fd file descriptor is not an eventfd file.
 */
struct file *eventfd_fget(int fd)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * eventfd_ctx_fdget - Acquires a reference to the internal eventfd context.
 * @fd: [in] Eventfd file descriptor.
 *
 * Returns a pointer to the internal eventfd context, otherwise the error
 * pointers returned by the following functions:
 *
 * eventfd_fget
 */
struct eventfd_ctx *eventfd_ctx_fdget(int fd)
{ … }
EXPORT_SYMBOL_GPL(…);

/**
 * eventfd_ctx_fileget - Acquires a reference to the internal eventfd context.
 * @file: [in] Eventfd file pointer.
 *
 * Returns a pointer to the internal eventfd context, otherwise the error
 * pointer:
 *
 * -EINVAL   : The @fd file descriptor is not an eventfd file.
 */
struct eventfd_ctx *eventfd_ctx_fileget(struct file *file)
{ … }
EXPORT_SYMBOL_GPL(…);

static int do_eventfd(unsigned int count, int flags)
{ … }

SYSCALL_DEFINE2(eventfd2, unsigned int, count, int, flags)
{ … }

SYSCALL_DEFINE1(eventfd, unsigned int, count)
{ … }