Critical Sections

• Critical sections are blocks of code that should not be interrupted.
• They are protected by turning interrupts on and off. Big hammer because they disable all interrupts on the system.
• Quicker then semaphores.
• Okay to use for quick things such as setting globals, updating small sections.
• Use just around the important parts in a function.

Requirements for critical sections

• Mutual exclusion - safe from interruption.
• Progress - no blocking.
• Bound waiting - quick.

Functions

• OS_ENTER_CRITICAL() - called right before critical code.
• OS_EXIT_CRITICAL() - called rigth after critical code.