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#ifndef MUTEX_H
#define MUTEX_H
class Mutex {
private:
uint8_t locked;
public:
Mutex() : locked(0) {}
Mutex(uint8_t l) : locked(l) {}
bool trylock() {
uint8_t val;
// Check if mutex is locked.
asm volatile ("ldrexb %0, [%1]" : "=r" (val) : "r" (&locked));
if(val) {
return false;
}
// Try taking the lock.
asm volatile ("strexb %0, %1, [%2]" : "=r" (val) : "r" (1), "r" (&locked));
if(val) {
return false;
}
asm volatile("dmb");
return true;
}
void lock() {
while(!trylock()) {
Thread::yield();
}
}
void unlock() {
asm volatile("dmb");
locked = 0;
}
};
#endif
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