Comtrol eCos - Manual (Page 71)

Condition Variables
Name
cyg_cond_init, cyg_cond_destroy, cyg_cond_wait, cyg_cond_timed_wait,
cyg_cond_signal, cyg_cond_broadcast — Synchronization primitive
Synopsis
#include < cyg/kernel/kapi.h >
void cyg_cond_init(cyg_cond_t* cond, cyg_mutex_t* mutex);
void cyg_cond_destroy(cyg_cond_t* cond);
cyg_bool_t cyg_cond_wait(cyg_cond_t* cond);
cyg_bool_t cyg_cond_timed_wait(cyg_cond_t* cond, cyg_tick_count_t abstime);
void cyg_cond_signal(cyg_cond_t* cond);
void cyg_cond_broadcast(cyg_cond_t* cond);
Description
Condition variables are used in conjunction with mutexes to implement long-term waits for some condition to
become true. For example consider a set of functions that control access to a pool of resources:
cyg_mutex_t res_lock;
res_t res_pool[RES_MAX];
int res_count = RES_MAX;
void res_init(void)
{
cyg_mutex_init(&res_lock);
< fill pool with resources >
}
res_t res_allocate(void)
{
res_t res;
cyg_mutex_lock(&res_lock); // lock the mutex
if( res_count == 0 ) // check for free resource
res = RES_NONE; // return RES_NONE if none
else
{
res_count--; // allocate a resources
res = res_pool[res_count];
}
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