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<concept xml:lang="en" id="GUID-088DC096-0CC7-5510-8D71-7DAF5961A681"><title>Using Critical Sections</title><prolog><metadata><keywords/></metadata></prolog><conbody><p>Critical sections are provided to serialise access to shared resources. They are Kernel objects and, as such, are managed by the Kernel.</p> <p>A critical section can only be used by threads within the same process; it <i>cannot</i> be used to control access to a resource shared by threads across different processes. To serialise access to a resource shared by threads across more than one process, use a mutex.</p> <p>While a critical section is used to serialise access to a general resource, it is used, typically, to serialise access to a section of re-entrant code which cannot be executed concurrently by more than one thread within a process. A critical section only allows one thread into a controlled section, forcing other threads, that try to gain access to that critical section, to wait until the first thread has exited from that section.</p> <p>Note that threads which do not attempt to gain access to the critical section are not blocked.</p> <p>A critical section is implemented using a semaphore.</p> <p>Access to a critical section object is through an <codeph>RCriticalSection</codeph> handle.</p> </conbody></concept>