What is a critical section and how is it implemented?

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What is a critical section and how is it implemented?..

Critical Section:-
In concurrent programming a critical section is a piece of
code that accesses a shared resource (data structure or
device) that must not be concurrently accessed by more than
one thread of execution. A critical section will usually
terminate in fixed time, and a thread, task or process will
only have to wait a fixed time to enter it. Some
synchronization mechanism is required at the entry and exit
of the critical section to ensure exclusive use.
for example a printer, can only be accessed by one process
at a time.
Example Code For Critical Sections with Win32 API: -
#include <windows.h>
CRITICAL_SECTION cs; /* This is the critical section
object -- once initialized, it cannot
be moved in memory */
/* Initialize the critical section -- This must be done
before locking */
InitializeCriticalSection(&cs);

/* Enter the critical section -- other threads are locked
out */
EnterCriticalSection(&cs);

/* Do some thread-safe processing! */

/* Leave the critical section -- other threads can now
EnterCriticalSection() */
LeaveCriticalSection(&cs);

/* Release system object when all finished -- usually at
the end of the cleanup code */
DeleteCriticalSection(&cs);

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What is a critical section and how is it implemented?..

Answer / umesh

Critical Section allows you to explicitly lock any resources so that untill u release the lock no body else can able to access it. Resource can be any thing. for example a variable, or a piece of code..

We can use Either CRITICAL_SECTION structure with the help of EnterCriticalSection and LeaveCriticalSection APIs.
Or MFC wrapper, CCriticalSection type variable. which gives u lock and unlock mechanism

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