path: root/fs/select.c

// SPDX-License-Identifier: GPL-2.0
/*
 * This file contains the procedures for the handling of select and poll
 *
 * Created for Linux based loosely upon Mathius Lattner's minix
 * patches by Peter MacDonald. Heavily edited by Linus.
 *
 *  4 February 1994
 *     COFF/ELF binary emulation. If the process has the STICKY_TIMEOUTS
 *     flag set in its personality we do *not* modify the given timeout
 *     parameter to reflect time remaining.
 *
 *  24 January 2000
 *     Changed sys_poll()/do_poll() to use PAGE_SIZE chunk-based allocation 
 *     of fds to overcome nfds < 16390 descriptors limit (Tigran Aivazian).
 */

#include <linux/kernel.h>
#include <linux/sched/signal.h>
#include <linux/sched/rt.h>
#include <linux/syscalls.h>
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/poll.h>
#include <linux/personality.h> /* for STICKY_TIMEOUTS */
#include <linux/file.h>
#include <linux/fdtable.h>
#include <linux/fs.h>
#include <linux/rcupdate.h>
#include <linux/hrtimer.h>
#include <linux/freezer.h>
#include <net/busy_poll.h>
#include <linux/vmalloc.h>

#include <linux/uaccess.h>

__poll_t vfs_poll(struct file *file, struct poll_table_struct *pt)
{
	if (file->f_op->poll) {
		return file->f_op->poll(file, pt);
	} else if (file_has_poll_mask(file)) {
		unsigned int events = poll_requested_events(pt);
		struct wait_queue_head *head;

		if (pt && pt->_qproc) {
			head =