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In a system where every thread holds at most one lock at a time, deadlock is impossible.

Consider the following program: int x = 0; void *worker(void *arg) { x = x + 1; return NULL; } int main() { pthread_t t1, t2; pthread_create(&t1, NULL, worker, NULL); pthread_create(&t2, NULL, worker, NULL); pthread_join(t1, NULL); pthread_join(t2, NULL); printf(“%d\n”, x); return 0; } Which of the following best describes the behavior of this program?

Does Lock A provide mutual exclusion?

Locks prevent the OS scheduler from performing a context switch during a critical section.

When the OS switches between two threads in the same process, it must flush the TLB.

For questions 23–24, consider the following code snippet: int bytesLeft = MAX_HEAP_SIZE; cond_t c; mutex_t m; void* allocate(int size) { mutex_lock(&m); while (bytesLeft < size) cond_wait(&c, &m); void *ptr = ...; // get mem from heap bytesLeft -= size; mutex_unlock(&m); return ptr; } void free(void *ptr, int size) { mutex_lock(&m); bytesLeft += size; cond_signal(&c); mutex_unlock(&m); }

A spinlock implemented with an atomic compare-and-swap (CAS) provides bounded waiting (no starvation).

You want to use condition variables to implement a traffic light controller for a standard traffic light with three colors (red, green, yellow). Waiting cars can only go when the light is green. Which of these is a possible correct use of condition variables?

Would you personally have rather lived in Ancient Athens or Ancient Sparta? Why?

How did Plato and Aristotle approach philosophy differently?