chbsem.h File Reference

Binary semaphores structures and macros. More...

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Data Structures
struct	ch_binary_semaphore
	Binary semaphore type. More...

Macros
#define	_BSEMAPHORE_DATA(name, taken)   {_SEMAPHORE_DATA(name.sem, ((taken) ? 0 : 1))}
	Data part of a static semaphore initializer. More...
#define	BSEMAPHORE_DECL(name, taken)   binary_semaphore_t name = _BSEMAPHORE_DATA(name, taken)
	Static semaphore initializer. More...

Typedefs
typedef struct ch_binary_semaphore	binary_semaphore_t
	Binary semaphore type. More...

Functions
static void	chBSemObjectInit (binary_semaphore_t *bsp, bool taken)
	Initializes a binary semaphore. More...
static msg_t	chBSemWait (binary_semaphore_t *bsp)
	Wait operation on the binary semaphore. More...
static msg_t	chBSemWaitS (binary_semaphore_t *bsp)
	Wait operation on the binary semaphore. More...
static msg_t	chBSemWaitTimeoutS (binary_semaphore_t *bsp, sysinterval_t timeout)
	Wait operation on the binary semaphore. More...
static msg_t	chBSemWaitTimeout (binary_semaphore_t *bsp, sysinterval_t timeout)
	Wait operation on the binary semaphore. More...
static void	chBSemResetI (binary_semaphore_t *bsp, bool taken)
	Reset operation on the binary semaphore. More...
static void	chBSemReset (binary_semaphore_t *bsp, bool taken)
	Reset operation on the binary semaphore. More...
static void	chBSemSignalI (binary_semaphore_t *bsp)
	Performs a signal operation on a binary semaphore. More...
static void	chBSemSignal (binary_semaphore_t *bsp)
	Performs a signal operation on a binary semaphore. More...
static bool	chBSemGetStateI (const binary_semaphore_t *bsp)
	Returns the binary semaphore current state. More...

Detailed Description

Binary semaphores structures and macros.

Binary semaphores related APIs and services.

Operation mode

Binary semaphores are implemented as a set of inline functions that use the existing counting semaphores primitives. The difference between counting and binary semaphores is that the counter of binary semaphores is not allowed to grow above the value 1. Repeated signal operation are ignored. A binary semaphore can thus have only two defined states:

• Taken, when its counter has a value of zero or lower than zero. A negative number represent the number of threads queued on the binary semaphore.
• Not taken, when its counter has a value of one.

Binary semaphores are different from mutexes because there is no concept of ownership, a binary semaphore can be taken by a thread and signaled by another thread or an interrupt handler, mutexes can only be taken and released by the same thread. Another difference is that binary semaphores, unlike mutexes, do not implement the priority inheritance protocol.
In order to use the binary semaphores APIs the CH_CFG_USE_SEMAPHORES option must be enabled in chconf.h.

Definition in file chbsem.h.