Semaphores

Collaboration diagram for Semaphores:

Functions
err_t	sys_sem_new (sys_sem_t *sem, u8_t count)
void	sys_sem_signal (sys_sem_t *sem)
u32_t	sys_arch_sem_wait (sys_sem_t *sem, u32_t timeout)
void	sys_sem_free (sys_sem_t *sem)
int	sys_sem_valid (sys_sem_t *sem)
void	sys_sem_set_invalid (sys_sem_t *sem)

Detailed Description

Function Documentation

sys_sem_new()

err_t sys_sem_new	(	sys_sem_t *	sem,
		u8_t	count
	)

Create a new semaphore

Parameters

sem	pointer to the semaphore to create
count	initial count of the semaphore

Returns

ERR_OK if successful, another err_t otherwise

{
  osSemaphoreDef(SEM);
 
  *sem = osSemaphoreCreate (osSemaphore(SEM), 1);
 
  if(*sem == NULL)
  {
#if SYS_STATS
      ++lwip_stats.sys.sem.err;
#endif /* SYS_STATS */
        return ERR_MEM;
  }
 
  if(count == 0)    // Means it can't be taken
  {
    osSemaphoreWait(*sem,0);
  }
 
#if SYS_STATS
    ++lwip_stats.sys.sem.used;
    if (lwip_stats.sys.sem.max < lwip_stats.sys.sem.used) {
        lwip_stats.sys.sem.max = lwip_stats.sys.sem.used;
    }
#endif /* SYS_STATS */
 
    return ERR_OK;
}

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sys_sem_signal()

void sys_sem_signal

(

sys_sem_t *

sem

)

Signals a semaphore

Parameters

sem	the semaphore to signal

{
  osSemaphoreRelease(*sem);
}

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sys_arch_sem_wait()

u32_t sys_arch_sem_wait	(	sys_sem_t *	sem,
		u32_t	timeout
	)

Wait for a semaphore for the specified timeout

Parameters

sem	the semaphore to wait for
timeout	timeout in milliseconds to wait (0 = wait forever)

Returns

time (in milliseconds) waited for the semaphore or SYS_ARCH_TIMEOUT on timeout

{
  uint32_t starttime = osKernelSysTick();
 
  if(timeout != 0)
  {
    if(osSemaphoreWait (*sem, timeout) == osOK)
    {
      return (osKernelSysTick() - starttime);
    }
    else
    {
      return SYS_ARCH_TIMEOUT;
    }
  }
  else
  {
    while(osSemaphoreWait (*sem, osWaitForever) != osOK);
    return (osKernelSysTick() - starttime);
  }
}

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sys_sem_free()

void sys_sem_free

(

sys_sem_t *

sem

)

Delete a semaphore

Parameters

sem	semaphore to delete

{
#if SYS_STATS
  --lwip_stats.sys.sem.used;
#endif /* SYS_STATS */
 
  osSemaphoreDelete(*sem);
}

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sys_sem_valid()

int sys_sem_valid

(

sys_sem_t *

sem

)

Check if a semaphore is valid/allocated: return 1 for valid, 0 for invalid

{
  if (*sem == SYS_SEM_NULL)
    return 0;
  else
    return 1;
}

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sys_sem_set_invalid()

void sys_sem_set_invalid

(

sys_sem_t *

sem

)

Set a semaphore invalid so that sys_sem_valid returns 0

{
  *sem = SYS_SEM_NULL;
}