FUTEX APIs

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

Detailed Description

Function Documentation

k_futex_wait()

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

#include <zephyr/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	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 <zephyr/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.