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>Synchronization [POSIX Section 11]</TITLE
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NAME="POSIX-SYNCHRONIZATION">Synchronization &#0091;POSIX Section 11&#0093;</H1
><DIV
CLASS="SECT2"
><H2
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><A
NAME="AEN13150">Functions Implemented</H2
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>int sem&#0095;init(sem&#0095;t &#0042;sem, int pshared, unsigned int value); 
int sem&#0095;destroy(sem&#0095;t &#0042;sem); 
int sem&#0095;wait(sem&#0095;t &#0042;sem); 
int sem&#0095;trywait(sem&#0095;t &#0042;sem); 
int sem&#0095;post(sem&#0095;t &#0042;sem);
int sem&#0095;getvalue(sem&#0095;t &#0042;sem, int &#0042;sval); 
int pthread&#0095;mutexattr&#0095;init( pthread&#0095;mutexattr&#0095;t &#0042;attr); 
int pthread&#0095;mutexattr&#0095;destroy( pthread&#0095;mutexattr&#0095;t &#0042;attr); 
int pthread&#0095;mutex&#0095;init(pthread&#0095;mutex&#0095;t &#0042;mutex,
	               const pthread&#0095;mutexattr&#0095;t &#0042;mutex&#0095;attr); 
int pthread&#0095;mutex&#0095;destroy(pthread&#0095;mutex&#0095;t &#0042;mutex); 
int pthread&#0095;mutex&#0095;lock(pthread&#0095;mutex&#0095;t &#0042;mutex); 
int pthread&#0095;mutex&#0095;trylock(pthread&#0095;mutex&#0095;t &#0042;mutex); 
int pthread&#0095;mutex&#0095;unlock(pthread&#0095;mutex&#0095;t &#0042;mutex); 
int pthread&#0095;condattr&#0095;init(pthread&#0095;condattr&#0095;t &#0042;attr); 
int pthread&#0095;condattr&#0095;destroy(pthread&#0095;condattr&#0095;t &#0042;attr); 
int pthread&#0095;cond&#0095;init(pthread&#0095;cond&#0095;t &#0042;cond, 
	               const pthread&#0095;condattr&#0095;t &#0042;attr); 
int pthread&#0095;cond&#0095;destroy(pthread&#0095;cond&#0095;t &#0042;cond); 
int pthread&#0095;cond&#0095;signal(pthread&#0095;cond&#0095;t &#0042;cond); 
int pthread&#0095;cond&#0095;broadcast(pthread&#0095;cond&#0095;t &#0042;cond); 
int pthread&#0095;cond&#0095;wait(pthread&#0095;cond&#0095;t &#0042;cond, 
	               pthread&#0095;mutex&#0095;t &#0042;mutex);
int pthread&#0095;cond&#0095;timedwait(pthread&#0095;cond&#0095;t &#0042;cond,
	                   pthread&#0095;mutex&#0095;t &#0042;mutex,
	                   const struct timespec &#0042;abstime);</PRE
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>sem&#0095;t &#0042;sem&#0095;open(const char &#0042;name, int oflag, ...);		&#0047;&#0047; TBA 
int sem&#0095;close(sem&#0095;t &#0042;sem);					&#0047;&#0047; TBA 
int sem&#0095;unlink(const char &#0042;name);				&#0047;&#0047; TBA 
int pthread&#0095;mutexattr&#0095;getpshared( const pthread&#0095;mutexattr&#0095;t &#0042;attr,
	                          int &#0042;pshared );
int pthread&#0095;mutexattr&#0095;setpshared( const pthread&#0095;mutexattr&#0095;t &#0042;attr,
	                          int pshared );
int  pthread&#0095;condattr&#0095;getpshared( const pthread&#0095;condattr&#0095;t &#0042;attr, 
	                          int &#0042;pshared);
int  pthread&#0095;condattr&#0095;setpshared( const pthread&#0095;condattr&#0095;t &#0042;attr,
	                          int pshared);</PRE
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NAME="AEN13156">Notes</H2
><P
></P
><UL
><LI
><P
>	    The presence of semaphores is controlled by the
	    CYGPKG&#0095;POSIX&#0095;SEMAPHORES option. This in turn
	    causes the &#0095;POSIX&#0095;SEMAPHORES feature test
	    macro to be defined and the semaphore API to be made
	    available.
	    </P
></LI
><LI
><P
>	    The <SPAN
CLASS="strong"
><B
CLASS="EMPHASIS"
>pshared</B
></SPAN
> argument to
	    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>sem&#0095;init()</I
></SPAN
> is not implemented,
	    its value is ignored.
	    </P
></LI
><LI
><P
>	    Functions <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>sem&#0095;open()</I
></SPAN
>, 
	    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>sem&#0095;close()</I
></SPAN
> and
	    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>sem&#0095;unlink()</I
></SPAN
> are present but
	    always return an error (ENOSYS).
	    </P
></LI
><LI
><P
>	    The exact priority inversion protocols supported may be
	    controlled with the
	    &#0095;POSIX&#0095;THREAD&#0095;PRIO&#0095;INHERIT and
	    &#0095;POSIX&#0095;THREAD&#0095;PRIO&#0095;PROTECT
	    configuration options.
	    </P
></LI
><LI
><P
>	    &#0123;&#0095;POSIX&#0095;THREAD&#0095;PROCESS&#0095;SHARED&#0125; is
	    not defined, so the 
	    <SPAN
CLASS="strong"
><B
CLASS="EMPHASIS"
>process-shared</B
></SPAN
> mutex
	    and condition variable attributes are not supported, and
	    neither are the functions
	    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>pthread&#0095;mutexattr&#0095;getpshared()</I
></SPAN
>,
	    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>pthread&#0095;mutexattr&#0095;setpshared()</I
></SPAN
>, 
	    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>pthread&#0095;condattr&#0095;getpshared()</I
></SPAN
> and 
	    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>pthread&#0095;condattr&#0095;setpshared()</I
></SPAN
>. 
	    </P
></LI
><LI
><P
>	    Condition variables do not become bound to a particular
	    mutex when
	    <SPAN
CLASS="emphasis"
><I
CLASS="EMPHASIS"
>pthread&#0095;cond&#0095;wait()</I
></SPAN
> is
	    called. Hence different threads may wait on a condition
	    variable with different mutexes. This is at variance with
	    the standard, which requires a condition variable to
	    become (dynamically) bound by the first waiter, and
	    unbound when the last finishes. However, this difference
	    is largely benign, and the cost of policing this feature
	    is non-trivial.
	  </P
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