Peterson's Soltuion

Introduction:

Peterson's solution provides a good algorithmic description of solving the critical-section problem and illustrates some of the complexities involved in designing software that addresses the requirements of mutual exclusion, progress, and bounded waiting. Peterson's algorithm is considered a standard low-level algorithm for two-thread mutual exclusion.

P0 execution

• Process P0 is initiated and has entered the Start state.
• Process P0 after a certain instant of time, enters Critical section.
• Since, Critical section is already occupied by Process P0, it is now time to trigger Process P1.

P1 Trigger

• Process P1 is triggered.
• Process P1 awaits in Start state as Critical section is already occupied by Process P0.
• Process P0 has exited the Critical section and hence, Process P1 can now enter the Critical state.
• Process P1 enters the Critical section, meanwhile Process P0 executes and enters the Exit state.
• Process P1 exits the Critical section and executes to enter the Exit state and meanwhile Process P0 has completed.
• Process P1 has completed.

Analysis of Peterson Algorithm approach

• Mutual Exclusion:

  The method provides mutual exclusion for sure. In entry section, the while condition involves the criteria for two variables therefore a process cannot enter in the critical section until the other process is interested and the process is the last one to update turn variable.

• Progress:

  An uninterested process will never stop the other interested process from entering in the critical section. If the other process is also interested then the process will wait.

• Bounded waiting:

  The interested variable mechanism failed because it was not providing bounded waiting. However, in Peterson solution, A deadlock can never happen because the process which first sets the turn variable will enter in the critical section for sure.

• Portability:

  This is the complete software solution and therefore it is portable on every hardware.