Operating System Solution - Semaphore

• Synchronization tool that does not require busy waiting.

• Can only be accessed via two atomic operations, which logically look like this:

s : integer

wait(s): while s ? 0 do no-op

s := s - 1;

signal(s): s:= s + 1;

mutex : semaphore :=1;

Repeat

wait( mutex );

critical section

signal( mutex );

remainder section

Forever

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