[Overview][Constants][Types][Classes][Procedures and functions][Variables][Index] | Reference for unit 'System' (#rtl)

# EnterCriticalSection

Enter a critical section

## Declaration

Source position: threadh.inc line 169

`procedure EnterCriticalSection(`
`var cs: TRTLCRITICALSECTION`
`);`

## Description

EnterCriticalSection will suspend the current thread if another thread has currently entered the critical section. When the other thread has left the critical section (through LeaveCriticalSection), the current thread resumes execution. The result is that only 1 thread is executing code which is protected by a EnterCriticalsection and LeaveCriticalSection pair.

The critical section must have been initialized with InitCriticalSection prior to a call to EnterCriticalsection.

A call to EnterCriticalsection must always be matched by a call to LeaveCriticalSection. To avoid problems, it is best to include the code to be execute in a try...finally block, as follows:

    EnterCriticalSection(Section);
      Try
        // Code to be protected goes here.
      Finally
        LeaveCriticalSection(Section);
      end;

For performance reasons it is best to limit the code between the entering and leaving of a critical section as short as possible.

## See also

InitCriticalsection |  | Initialize a critical section
DoneCriticalsection |  | Clean up a critical section.
LeaveCriticalsection |  | Leave a critical section