59 lines
2.4 KiB
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59 lines
2.4 KiB
HTML
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<!--Converted with LaTeX2HTML 96.1-c (Feb 29, 1996) by Nikos Drakos (nikos@cbl.leeds.ac.uk), CBLU, University of Leeds -->
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<TITLE>Kernel sem structure</TITLE>
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<A NAME="tex2html1002" HREF="node51.html"><IMG WIDTH=37 HEIGHT=24 ALIGN=BOTTOM ALT="next" SRC="next_motif.gif"></A> <A NAME="tex2html1000" HREF="node48.html"><IMG WIDTH=26 HEIGHT=24 ALIGN=BOTTOM ALT="up" SRC="up_motif.gif"></A> <A NAME="tex2html996" HREF="node49.html"><IMG WIDTH=63 HEIGHT=24 ALIGN=BOTTOM ALT="previous" SRC="previous_motif.gif"></A> <A NAME="tex2html1004" HREF="node1.html"><IMG WIDTH=65 HEIGHT=24 ALIGN=BOTTOM ALT="contents" SRC="contents_motif.gif"></A> <BR>
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<B> Next:</B> <A NAME="tex2html1003" HREF="node51.html">SYSTEM CALL: semget()</A>
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<B>Up:</B> <A NAME="tex2html1001" HREF="node48.html">Internal Data Structures</A>
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<B> Previous:</B> <A NAME="tex2html997" HREF="node49.html">Kernel semid_ds structure</A>
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<BR> <P>
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<H4><A NAME="SECTION00743220000000000000">Kernel <TT>sem</TT> structure</A></H4>
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<P>
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In the <TT>semid_ds</TT> structure, there exists a pointer to the base of the semaphore array
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itself. Each array member is of the <TT>sem</TT> structure type. It is also defined in
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<TT>linux/sem.h</TT>:
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<P>
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<P>
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<HR><PRE> /* One semaphore structure for each semaphore in the system. */
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struct sem {
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short sempid; /* pid of last operation */
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ushort semval; /* current value */
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ushort semncnt; /* num procs awaiting increase in semval */
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ushort semzcnt; /* num procs awaiting semval = 0 */
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};</PRE>
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<HR><DL ><DT><STRONG><TT>sem_pid</TT></STRONG>
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<DD>
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<P>
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The PID (process ID) that performed the last operation
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<P>
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<DT><STRONG><TT>sem_semval</TT></STRONG>
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<DD>
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<P>
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The current value of the semaphore
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<P>
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<DT><STRONG><TT>sem_semncnt</TT></STRONG>
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<DD>
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<P>
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Number of processes waiting for resources to become available
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<P>
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<DT><STRONG><TT>sem_semzcnt</TT></STRONG>
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<DD>
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<P>
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Number of processes waiting for 100% resource utilization
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<P>
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</DL><BR> <HR>
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<P><ADDRESS>
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<I>Converted on: <BR>
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Fri Mar 29 14:43:04 EST 1996</I>
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