Managing Milk Mishaps: Concurrency Lessons
Explore the humorous journey of roommates handling milk shortages in a series of concurrency scenarios. Follow along as they navigate store runs and synchronized milk purchases, illustrated with engaging lecture slides from CS 111.
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Presentation Transcript
Too Much Milk Roommate A Arrive home: no milk Leave for store Arrive at store Leave store Arrive home, put milk away 3:00 3:05 3:10 3:15 3:20 3:25 3:30 CS 111 Lecture Notes: Concurrency Slide 1
Too Much Milk Roommate A Arrive home: no milk Leave for store Arrive at store Leave store Arrive home, put milk away Roommate B 3:00 3:05 3:10 3:15 3:20 3:25 3:30 Arrive home: no milk Leave for store Arrive at store Leave store Arrive home: too much milk! CS 111 Lecture Notes: Concurrency Slide 2
Computerized Milk Purchase 1 if (milk == 0) { 2 if (note == 0) { 3 note = 1; 4 buy_milk(); 5 note = 0; 6 } 7 } CS 111 Lecture Notes: Concurrency Slide 3
Still Too Much Milk Thread A: 1 if (milk == 0) { 2 if (note == 0) { 3 4 5 6 7 8 9 10 note = 1; 11 buy_milk(); 12 note = 0; 13 } 14 } Thread B: if (milk == 0) { if (note == 0) { note = 1; buy_milk(); note = 0; } } CS 111 Lecture Notes: Concurrency Slide 4
Second Attempt Thread A: 1 if (note == 0) { 2 if (milk == 0) { 3 buy_milk(); 4 } 5 note = 1; 6 } Thread B: 1 if (note == 1) { 2 if (milk == 0) { 3 buy_milk(); 4 } 5 note = 0; 6 } CS 111 Lecture Notes: Concurrency Slide 5
Third Attempt Thread A: 1 noteA = 1; 2 if (noteB == 0) { 3 if (milk == 0) { 4 buy_milk(); 5 } 6 } 7 noteA = 0; Thread B: 1 noteB = 1; 2 if (noteA == 0) { 3 if (milk == 0) { 4 buy_milk(); 5 } 6 } 7 noteB = 0; CS 111 Lecture Notes: Concurrency Slide 6
Fourth Attempt Thread A: 1 noteA = 1; 2 if (noteB == 0) { 3 if (milk == 0) { 4 buy_milk(); 5 } 6 } 7 noteA = 0; Thread B: 1 noteB = 1; 2 while (noteA == 1) { 3 // do nothing 4 } 5 if (milk == 0) { 6 buy_milk(); 7 } 8 noteB = 0; CS 111 Lecture Notes: Concurrency Slide 7
