FUTEX APIs

Functions
int	k_futex_wait (struct k_futex *futex, int expected, k_timeout_t timeout)
	Pend the current thread on a futex. More...
int	k_futex_wake (struct k_futex *futex, bool wake_all)
	Wake one/all threads pending on a futex. More...

Detailed Description

Function Documentation

k_futex_wait()

int k_futex_wait	(	struct k_futex *	futex,
		int	expected,
		k_timeout_t	timeout
	)

#include <include/kernel.h>

Pend the current thread on a futex.

Tests that the supplied futex contains the expected value, and if so, goes to sleep until some other thread calls k_futex_wake() on it.

Parameters

futex	Address of the futex.
expected	Expected value of the futex, if it is different the caller will not wait on it.
timeout	Non-negative waiting period on the futex, or one of the special values K_NO_WAIT or K_FOREVER.

Return values

-EACCES	Caller does not have read access to futex address.
-EAGAIN	If the futex value did not match the expected parameter.
-EINVAL	Futex parameter address not recognized by the kernel.
-ETIMEDOUT	Thread woke up due to timeout and not a futex wakeup.
0	if the caller went to sleep and was woken up. The caller should check the futex's value on wakeup to determine if it needs to block again.

k_futex_wake()

int k_futex_wake	(	struct k_futex *	futex,
		bool	wake_all
	)

#include <include/kernel.h>

Wake one/all threads pending on a futex.

Wake up the highest priority thread pending on the supplied futex, or wakeup all the threads pending on the supplied futex, and the behavior depends on wake_all.

Parameters

futex	Futex to wake up pending threads.
wake_all	If true, wake up all pending threads; If false, wakeup the highest priority thread.

Return values

-EACCES	Caller does not have access to the futex address.
-EINVAL	Futex parameter address not recognized by the kernel.
Number	of threads that were woken up.