12 <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>

    12 <concept id="GUID-088DC096-0CC7-5510-8D71-7DAF5961A681" xml:lang="en"><title>Using

    13 Critical Sections</title><shortdesc>This document describes how to use critical sections.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

    14 <p>Critical sections are provided to serialise access to shared resources.

    15 They are Kernel objects and, as such, are managed by the Kernel.</p>

    16 <p>A critical section can only be used by threads within the same process;

    17 it <i>cannot</i> be used to control access to a resource shared by threads

    18 across different processes. To serialise access to a resource shared by threads

    19 across more than one process, use a mutex.</p>

    20 <p>While a critical section is used to serialise access to a general resource,

    21 it is used, typically, to serialise access to a section of re-entrant code

    22 which cannot be executed concurrently by more than one thread within a process.

    23 A critical section only allows one thread into a controlled section, forcing

    24 other threads, that try to gain access to that critical section, to wait until

    25 the first thread has exited from that section.</p>

    26 <p>Note that threads which do not attempt to gain access to the critical section

    27 are not blocked.</p>

    28 <p>A critical section is implemented using a semaphore.</p>

    29 <p>Access to a critical section object is through an <codeph>RCriticalSection</codeph> handle.</p>

    30 </conbody></concept>