Zephyr API Documentation  3.7.0-rc3
A Scalable Open Source RTOS
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Semaphore APIs

Macros

#define K_SEM_MAX_LIMIT   UINT_MAX
 Maximum limit value allowed for a semaphore.
 
#define K_SEM_DEFINE(name, initial_count, count_limit)
 Statically define and initialize a semaphore.
 

Functions

int k_sem_init (struct k_sem *sem, unsigned int initial_count, unsigned int limit)
 Initialize a semaphore.
 
int k_sem_take (struct k_sem *sem, k_timeout_t timeout)
 Take a semaphore.
 
void k_sem_give (struct k_sem *sem)
 Give a semaphore.
 
void k_sem_reset (struct k_sem *sem)
 Resets a semaphore's count to zero.
 
unsigned int k_sem_count_get (struct k_sem *sem)
 Get a semaphore's count.
 

Detailed Description

Macro Definition Documentation

◆ K_SEM_DEFINE

#define K_SEM_DEFINE (   name,
  initial_count,
  count_limit 
)

#include <zephyr/kernel.h>

Value:
STRUCT_SECTION_ITERABLE(k_sem, name) = \
Z_SEM_INITIALIZER(name, initial_count, count_limit); \
BUILD_ASSERT(((count_limit) != 0) && \
((initial_count) <= (count_limit)) && \
((count_limit) <= K_SEM_MAX_LIMIT));
#define STRUCT_SECTION_ITERABLE(struct_type, varname)
Defines a new element for an iterable section.
Definition: iterable_sections.h:216
#define K_SEM_MAX_LIMIT
Maximum limit value allowed for a semaphore.
Definition: kernel.h:3154

Statically define and initialize a semaphore.

The semaphore can be accessed outside the module where it is defined using:

extern struct k_sem <name>;
Parameters
nameName of the semaphore.
initial_countInitial semaphore count.
count_limitMaximum permitted semaphore count.

◆ K_SEM_MAX_LIMIT

#define K_SEM_MAX_LIMIT   UINT_MAX

#include <zephyr/kernel.h>

Maximum limit value allowed for a semaphore.

This is intended for use when a semaphore does not have an explicit maximum limit, and instead is just used for counting purposes.

Function Documentation

◆ k_sem_count_get()

unsigned int k_sem_count_get ( struct k_sem *  sem)

#include <zephyr/kernel.h>

Get a semaphore's count.

This routine returns the current count of sem.

Parameters
semAddress of the semaphore.
Returns
Current semaphore count.

◆ k_sem_give()

void k_sem_give ( struct k_sem *  sem)

#include <zephyr/kernel.h>

Give a semaphore.

This routine gives sem, unless the semaphore is already at its maximum permitted count.

Function properties (list may not be complete)
isr-ok
Parameters
semAddress of the semaphore.

◆ k_sem_init()

int k_sem_init ( struct k_sem *  sem,
unsigned int  initial_count,
unsigned int  limit 
)

#include <zephyr/kernel.h>

Initialize a semaphore.

This routine initializes a semaphore object, prior to its first use.

Parameters
semAddress of the semaphore.
initial_countInitial semaphore count.
limitMaximum permitted semaphore count.
See also
K_SEM_MAX_LIMIT
Return values
0Semaphore created successfully
-EINVALInvalid values

◆ k_sem_reset()

void k_sem_reset ( struct k_sem *  sem)

#include <zephyr/kernel.h>

Resets a semaphore's count to zero.

This routine sets the count of sem to zero. Any outstanding semaphore takes will be aborted with -EAGAIN.

Parameters
semAddress of the semaphore.

◆ k_sem_take()

int k_sem_take ( struct k_sem *  sem,
k_timeout_t  timeout 
)

#include <zephyr/kernel.h>

Take a semaphore.

This routine takes sem.

Note
timeout must be set to K_NO_WAIT if called from ISR.
Function properties (list may not be complete)
isr-ok
Parameters
semAddress of the semaphore.
timeoutWaiting period to take the semaphore, or one of the special values K_NO_WAIT and K_FOREVER.
Return values
0Semaphore taken.
-EBUSYReturned without waiting.
-EAGAINWaiting period timed out, or the semaphore was reset during the waiting period.