wait.h File Reference

Go to the source code of this file.

Classes
struct	wait_queue_head_t
	Head of the waiting queue. More...
struct	wait_queue_entry_t
	Entry of the waiting queue. More...

Macros
#define	WNOHANG   0x00000001
	Return immediately if no child is there to be waited for.
#define	WUNTRACED   0x00000002
	Return for children that are stopped, and whose status has not been reported.
#define	WIFSIGNALED(status)   (!WIFSTOPPED(status) && !WIFEXITED(status))
	returns true if the child process exited because of a signal that was not caught.
#define	WIFSTOPPED(status)   (((status)&0xff) == 0x7f)
	returns true if the child process that caused the return is currently stopped; this is only possible if the call was done using WUNTRACED().
#define	WEXITSTATUS(status)   (((status)&0xff00) >> 8)
	evaluates to the least significant eight bits of the return code of the child that terminated, which may have been set as the argument to a call to exit() or as the argument for a return statement in the main program. This macro can only be evaluated if WIFEXITED() returned nonzero.
#define	WTERMSIG(status)   ((status)&0x7f)
	returns the number of the signal that caused the child process to terminate. This macro can only be evaluated if WIFSIGNALED() returned nonzero.
#define	WIFEXITED(status)   (WTERMSIG(status) == 0)
	Is nonzero if the child exited normally.
#define	WSTOPSIG(status)   (WEXITSTATUS(status))
	returns the number of the signal that caused the child to stop. This macro can only be evaluated if WIFSTOPPED() returned nonzero.
#define	TASK_RUNNING   0x00
	The process is either: 1) running on CPU or 2) waiting in a run queue.
#define	TASK_INTERRUPTIBLE   (1 << 0)
	The process is sleeping, waiting for some event to occur.
#define	TASK_UNINTERRUPTIBLE   (1 << 1)
	Similar to TASK_INTERRUPTIBLE, but it doesn't process signals.
#define	TASK_STOPPED   (1 << 2)
	Stopped, it's not running, and not able to run.
#define	TASK_TRACED   (1 << 3)
	Is being monitored by other processes such as debuggers.
#define	EXIT_ZOMBIE   (1 << 4)
	The process has terminated.
#define	EXIT_DEAD   (1 << 5)
	The final state.
#define	WQ_FLAG_EXCLUSIVE   0x01
	When an entry has this flag is added to the end of the wait queue. Entries without that flag are, instead, added to the beginning.

Typedefs
typedef struct wait_queue_head_t	wait_queue_head_t
	Head of the waiting queue.
typedef struct wait_queue_entry_t	wait_queue_entry_t
	Entry of the waiting queue.

Functions
wait_queue_entry_t *	wait_queue_entry_alloc (void)
	Allocates the memory for a wait_queue_entry. More...
void	wait_queue_entry_dealloc (wait_queue_entry_t *wait_queue_entry)
	Frees the memory of a wait_queue_entry. More...
void	init_waitqueue_entry (wait_queue_entry_t *wq, struct task_struct *task)
	Initialize the waiting queue entry. More...
void	add_wait_queue (wait_queue_head_t *head, wait_queue_entry_t *wq)
	Adds the element to the waiting queue. More...
void	remove_wait_queue (wait_queue_head_t *head, wait_queue_entry_t *wq)
	Removes the element from the waiting queue. More...
int	default_wake_function (wait_queue_entry_t *wait, unsigned mode, int sync)
	The default wake function, a wrapper for try_to_wake_up. More...
wait_queue_entry_t *	sleep_on (wait_queue_head_t *wq)
	Sets the state of the current process to TASK_UNINTERRUPTIBLE and inserts it into the specified wait queue. More...

Detailed Description

Copyright

(c) 2014-2024 This file is distributed under the MIT License. See LICENSE.md for details.

Function Documentation

add_wait_queue()

void add_wait_queue	(	wait_queue_head_t *	head,
		wait_queue_entry_t *	wq
	)

Adds the element to the waiting queue.

Parameters

head	The head of the waiting queue.
wq	The entry we insert inside the waiting queue.

default_wake_function()

int default_wake_function	(	wait_queue_entry_t *	wait,
		unsigned	mode,
		int	sync
	)

The default wake function, a wrapper for try_to_wake_up.

Parameters

wait	The pointer to the wait queue.
mode	The type of wait (TASK_INTERRUPTIBLE or TASK_UNINTERRUPTIBLE).
sync	Specifies if the wakeup should be synchronous.

Returns

1 on success, 0 on failure.

init_waitqueue_entry()

void init_waitqueue_entry	(	wait_queue_entry_t *	wq,
		struct task_struct *	task
	)

Initialize the waiting queue entry.

Parameters

wq	The entry we initialize.
task	The task associated with the entry.

remove_wait_queue()

void remove_wait_queue	(	wait_queue_head_t *	head,
		wait_queue_entry_t *	wq
	)

Removes the element from the waiting queue.

Parameters

head	The head of the waiting queue.
wq	The entry we remove from the waiting queue.

sleep_on()

wait_queue_entry_t* sleep_on

(

wait_queue_head_t *

wq

)

Sets the state of the current process to TASK_UNINTERRUPTIBLE and inserts it into the specified wait queue.

Parameters

wq	Waitqueue where to sleep.

Returns

Pointer to the entry inside the wq representing the sleeping process.

wait_queue_entry_alloc()

wait_queue_entry_t* wait_queue_entry_alloc

(

void

)

Allocates the memory for a wait_queue_entry.

Returns

a pointer to the allocated wait_queue_entry.

wait_queue_entry_dealloc()

void wait_queue_entry_dealloc

(

wait_queue_entry_t *

wait_queue_entry

)

Frees the memory of a wait_queue_entry.

Parameters

wait_queue_entry

pointer to the wait_queue_entry.