<concept xml:lang="en" id="GUID-B1C0C5E2-DC8D-5230-8D4B-338DF619F1D2"><title>Critical Sections Overview</title><prolog><metadata><keywords/></metadata></prolog><conbody><section><title>Purpose</title> <p>Synchronises exclusive access to shared resources within a single process. </p> </section> <section><title>Description</title> <p>Critical sections are typically used to serialize access to a section of re-entrant code that cannot be executed concurrently by more than one thread within a process. A critical section object only allows one thread into a controlled section, forcing other threads which attempt to gain access to that critical section to wait until the first thread has exited from that section.</p> <p>A critical section <i>cannot</i> be used to control access to a resource shared by threads across different processes. For that, use a mutex.</p> <p>Critical sections are Kernel objects and, as such, are managed by the Kernel, and accessed by user programs through handles. They are implemented using a semaphore. </p> <p>The critical section handle is provided by <xref href="GUID-FC5F1EC1-28CC-3B06-83C4-B90EF8EEBA07.dita"><apiname>RCriticalSection</apiname></xref>.</p> </section> </conbody></concept>