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Too Much Milk With Locks

Both threads: struct lock l; ... l ock_acquire (&l); if (milk == 0) { buy_milk (); } lock_release (& l);. Too Much Milk With Locks. char buffer[SIZE]; int count = 0; int head = 0, tail = 0; struct lock l; lock_init (&l); void put(char c) { lock_acquire (&l); count++;

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Too Much Milk With Locks

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  1. Both threads: struct lock l; ... lock_acquire(&l); if (milk == 0) { buy_milk(); } lock_release(&l); Too Much Milk With Locks CS 140 Lecture Notes: Concurrency

  2. char buffer[SIZE]; int count = 0; int head = 0, tail = 0; struct lock l; lock_init(&l); void put(char c) { lock_acquire(&l); count++; buffer[head] = c; head++; if (head == SIZE) { head = 0; } lock_release(&l); } char get() { char c; lock_acquire(&l); count--; c = buffer[tail]; tail++; if (tail == SIZE) { tail = 0; } lock_release(&l); return c; } Producer/Consumer, v1 CS 140 Lecture Notes: Locks

  3. char buffer[SIZE]; int count = 0; int head = 0, tail = 0; struct lock l; lock_init(&l); void put(char c) { lock_acquire(&l); while (count == SIZE) { lock_release(&l); lock_acquire(&l); } count++; buffer[head] = c; head++; if (head == SIZE) { head = 0; } lock_release(&l); } char get() { char c; lock_acquire(&l); while (count == 0) { lock_release(&l); lock_acquire(&l); } count--; c = buffer[tail]; tail++; if (tail == SIZE) { tail = 0; } lock_release(&l); return c; } Producer/Consumer v2 CS 140 Lecture Notes: Locks

  4. char buffer[SIZE]; int count = 0; int head = 0, tail = 0; struct lock l; struct condition dataAvailable; struct condition spaceAvailable; lock_init(&l); cond_init(&dataAvailable); cond_init(&spaceAvailable); void put(char c) { lock_acquire(&l); while (count == SIZE) { cond_wait(&spaceAvailable, &l); } count++; buffer[head] = c; head++; if (head == SIZE) { head = 0; } cond_signal(&dataAvailable, &l); lock_release(&l); } char get() { char c; lock_acquire(&l); while (count == 0) { cond_wait(&dataAvailable, &l); } count--; c = buffer[tail]; tail++; if (tail == SIZE) { tail = 0; } cond_signal(&spaceAvailable, &l); lock_release(&l); return c; } Producer/Consumer v3 T1 T2 T3 CS 140 Lecture Notes: Locks

  5. CS 140 Lecture Notes: Locks

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