In concurrent programming, a code segment that accesses shared resources and must not be executed by more than one process or thread at a time.
In multithreaded programs, critical sections must be properly protected.
セマフォを使ってクリティカルセクションへの排他制御を行う。
Use semaphores to implement mutual exclusion for the critical section.
Variant with interpunct; less common in running text.
Borrowed from English 'critical section', a term from concurrent computing.