Problem with Strict Alternation as a Solution to

Problem with Strict Alternation as a Solution to Process Synchronization

Problem with Strict Alternation as a Solution to Process Synchronization

turn 0 Initial State main() { while (TRUE) { while (turn != 0) {}

turn 0 Initial State main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 0 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 0 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 0 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 0 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

turn 1 Sets turn to 1 main() { while (TRUE) { while (turn !=

turn 1 Sets turn to 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

turn 1 Value is 1. Wait. main() { while (TRUE) { while (turn !=

turn 1 Value is 1. Wait. main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

turn 1 Still 1. So, wait. main() { while (TRUE) { while (turn !=

turn 1 Still 1. So, wait. main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

turn 1 Still 1. So, wait. main() { while (TRUE) { while (turn !=

turn 1 Still 1. So, wait. main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

turn 1 Value is 1. So, carry on. main() { while (TRUE) { while

turn 1 Value is 1. So, carry on. main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

turn 1 Still 1. So, wait. main() { while (TRUE) { while (turn !=

turn 1 Still 1. So, wait. main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 1 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

turn 0 Sets turn to 0 main() { while (TRUE) { while (turn !=

turn 0 Sets turn to 0 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 0 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 0 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

turn 0 Value is now 0. So, carry on. main() { while (TRUE) {

turn 0 Value is now 0. So, carry on. main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

$turn 0 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn$

turn 0 main() { while (TRUE) { while (turn != 0) {} critical_region(); turn = 1; noncritical_region(); } } main() { while (TRUE) { while (turn != 1) {} critical_region(); turn = 0; noncritical_region(); } } noncritical_region() { //statement 1 //statement 2 //statement 3 //statement 4 //statement 5 } Process 0 Process 1

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