a C standard library for fx Casio calculators
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fxlibc/src/libc/threads/mutex.c

107 lines
2.3 KiB

#include <threads.h>
#include <unistd.h>
// Creates a new mutex object with type __TYPE.
// @note: If successful the new object is pointed by __MUTEX.
int mtx_init (mtx_t *__mutex, int __type)
{
// Check if the mutext is already initialized
if (__mutex->__watermark == MTX_WATERMARK)
return (-1);
// Initialize mutex
__mutex->__watermark = MTX_WATERMARK;
__mutex->type = __type;
__mutex->lock = 0;
return (0);
}
// Block the current thread until the mutex pointed to by __MUTEX is unlocked.
// In that case current thread will not be blocked.
int mtx_lock(mtx_t *__mutex)
{
// Check mutex validity
if (__mutex->__watermark != MTX_WATERMARK)
return (-1);
// Wait util the mutex is unlocked
while (1) {
// Check if the mutex is unlock
__thread_atomic_start();
if (__mutex->lock == 0)
break;
__thread_atomic_stop();
// TODO: force kernel schedule
__asm__ volatile ("sleep");
}
//TODO: handle mutex type !!
(void)__mutex->type;
// Lock the mutex
__mutex->lock = 1;
// Stop atomic operations
__thread_atomic_stop();
return (0);
}
// Try to lock the mutex pointed by __MUTEX without blocking.
// @note: If the mutex is free the current threads takes control of it,
// otherwise it returns immediately.
int mtx_trylock(mtx_t *__mutex)
{
// Check mutex validity
if (__mutex->__watermark != MTX_WATERMARK)
return (-1);
// Start atomic operations
__thread_atomic_start();
// Check if the mutex is already free
int ret = -1;
if (__mutex->lock == 0) {
//TODO: handle mutex type !!
(void)__mutex->type;
// lock the mutex and change the return value
__mutex->lock = 1;
ret = 0;
}
// Stop atomic operation and return
__thread_atomic_stop();
return (ret);
}
// Unlock the mutex pointed by __MUTEX.
// @note: It may potentially awake other threads waiting on this mutex.
int mtx_unlock(mtx_t *__mutex)
{
// Check mutex validity
if (__mutex->__watermark != MTX_WATERMARK)
return (-1);
// Start atomic operation
__thread_atomic_start();
// Check if the mutex is realy used and unluck if needed
int ret = -1;
if (__mutex->lock != 0) {
__mutex->lock = 0;
ret = 0;
}
// Stop atomic operation and return
__thread_atomic_stop();
return (ret);
}
// Destroy the mutex object pointed by __MUTEX.
// TODO: check if the mutex is in use ?
void mtx_destroy(mtx_t *__mutex)
{
__mutex->__watermark = 0x00000000;
__mutex->type = -1;
}