ardupilot/libraries/AP_HAL_Linux/Semaphores.cpp

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#include <AP_HAL/AP_HAL.h>
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#include "Semaphores.h"
extern const AP_HAL::HAL& hal;
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using namespace Linux;
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// construct a semaphore
Semaphore::Semaphore()
{
pthread_mutexattr_t attr;
pthread_mutexattr_init(&attr);
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
pthread_mutex_init(&_lock, &attr);
}
bool Semaphore::give()
{
return pthread_mutex_unlock(&_lock) == 0;
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}
bool Semaphore::take(uint32_t timeout_ms)
{
if (timeout_ms == HAL_SEMAPHORE_BLOCK_FOREVER) {
return pthread_mutex_lock(&_lock) == 0;
}
if (take_nonblocking()) {
return true;
}
uint64_t start = AP_HAL::micros64();
do {
hal.scheduler->delay_microseconds(200);
if (take_nonblocking()) {
return true;
}
} while ((AP_HAL::micros64() - start) < timeout_ms*1000);
return false;
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}
bool Semaphore::take_nonblocking()
{
return pthread_mutex_trylock(&_lock) == 0;
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}
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