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NAME="POSIX-SYNCHRONIZATION">Synchronization [POSIX Section 11]</H1
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NAME="POSIX-SYNCHRONIZATION">Synchronization [POSIX Section 11]</H1
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CLASS="SECT2"
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><H2
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><H2
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NAME="AEN13150">Functions Implemented</H2
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><PRE
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><PRE
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CLASS="SCREEN"
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CLASS="SCREEN"
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>int sem_init(sem_t *sem, int pshared, unsigned int value);
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>int sem_init(sem_t *sem, int pshared, unsigned int value);
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int sem_destroy(sem_t *sem);
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int sem_destroy(sem_t *sem);
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int sem_wait(sem_t *sem);
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int sem_wait(sem_t *sem);
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int sem_trywait(sem_t *sem);
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int sem_trywait(sem_t *sem);
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int sem_post(sem_t *sem);
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int sem_post(sem_t *sem);
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int sem_getvalue(sem_t *sem, int *sval);
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int sem_getvalue(sem_t *sem, int *sval);
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int pthread_mutexattr_init( pthread_mutexattr_t *attr);
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int pthread_mutexattr_init( pthread_mutexattr_t *attr);
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int pthread_mutexattr_destroy( pthread_mutexattr_t *attr);
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int pthread_mutexattr_destroy( pthread_mutexattr_t *attr);
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int pthread_mutex_init(pthread_mutex_t *mutex,
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int pthread_mutex_init(pthread_mutex_t *mutex,
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const pthread_mutexattr_t *mutex_attr);
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const pthread_mutexattr_t *mutex_attr);
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int pthread_mutex_destroy(pthread_mutex_t *mutex);
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int pthread_mutex_destroy(pthread_mutex_t *mutex);
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int pthread_mutex_lock(pthread_mutex_t *mutex);
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int pthread_mutex_lock(pthread_mutex_t *mutex);
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int pthread_mutex_trylock(pthread_mutex_t *mutex);
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int pthread_mutex_trylock(pthread_mutex_t *mutex);
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int pthread_mutex_unlock(pthread_mutex_t *mutex);
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int pthread_mutex_unlock(pthread_mutex_t *mutex);
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int pthread_condattr_init(pthread_condattr_t *attr);
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int pthread_condattr_init(pthread_condattr_t *attr);
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int pthread_condattr_destroy(pthread_condattr_t *attr);
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int pthread_condattr_destroy(pthread_condattr_t *attr);
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int pthread_cond_init(pthread_cond_t *cond,
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int pthread_cond_init(pthread_cond_t *cond,
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const pthread_condattr_t *attr);
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const pthread_condattr_t *attr);
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int pthread_cond_destroy(pthread_cond_t *cond);
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int pthread_cond_destroy(pthread_cond_t *cond);
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int pthread_cond_signal(pthread_cond_t *cond);
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int pthread_cond_signal(pthread_cond_t *cond);
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int pthread_cond_broadcast(pthread_cond_t *cond);
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int pthread_cond_broadcast(pthread_cond_t *cond);
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int pthread_cond_wait(pthread_cond_t *cond,
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int pthread_cond_wait(pthread_cond_t *cond,
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pthread_mutex_t *mutex);
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pthread_mutex_t *mutex);
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int pthread_cond_timedwait(pthread_cond_t *cond,
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int pthread_cond_timedwait(pthread_cond_t *cond,
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pthread_mutex_t *mutex,
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pthread_mutex_t *mutex,
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const struct timespec *abstime);</PRE
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const struct timespec *abstime);</PRE
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></TD
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CLASS="SECT2"
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><H2
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><H2
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CLASS="SECT2"
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CLASS="SECT2"
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><A
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><A
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NAME="AEN13153">Functions Omitted</H2
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NAME="AEN13153">Functions Omitted</H2
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><TABLE
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BORDER="5"
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><PRE
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><PRE
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CLASS="SCREEN"
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CLASS="SCREEN"
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>sem_t *sem_open(const char *name, int oflag, ...); // TBA
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>sem_t *sem_open(const char *name, int oflag, ...); // TBA
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int sem_close(sem_t *sem); // TBA
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int sem_close(sem_t *sem); // TBA
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int sem_unlink(const char *name); // TBA
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int sem_unlink(const char *name); // TBA
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int pthread_mutexattr_getpshared( const pthread_mutexattr_t *attr,
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int pthread_mutexattr_getpshared( const pthread_mutexattr_t *attr,
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int *pshared );
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int *pshared );
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int pthread_mutexattr_setpshared( const pthread_mutexattr_t *attr,
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int pthread_mutexattr_setpshared( const pthread_mutexattr_t *attr,
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int pshared );
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int pshared );
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int pthread_condattr_getpshared( const pthread_condattr_t *attr,
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int pthread_condattr_getpshared( const pthread_condattr_t *attr,
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int *pshared);
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int *pshared);
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int pthread_condattr_setpshared( const pthread_condattr_t *attr,
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int pthread_condattr_setpshared( const pthread_condattr_t *attr,
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int pshared);</PRE
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int pshared);</PRE
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></TD
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></TD
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></TR
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></TR
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></TABLE
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></TABLE
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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><H2
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CLASS="SECT2"
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CLASS="SECT2"
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><A
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><A
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NAME="AEN13156">Notes</H2
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NAME="AEN13156">Notes</H2
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><P
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><P
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></P
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></P
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><UL
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><UL
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><LI
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><LI
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><P
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><P
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> The presence of semaphores is controlled by the
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> The presence of semaphores is controlled by the
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CYGPKG_POSIX_SEMAPHORES option. This in turn
|
CYGPKG_POSIX_SEMAPHORES option. This in turn
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causes the _POSIX_SEMAPHORES feature test
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causes the _POSIX_SEMAPHORES feature test
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macro to be defined and the semaphore API to be made
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macro to be defined and the semaphore API to be made
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available.
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available.
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</P
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</P
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></LI
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></LI
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><LI
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><LI
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><P
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><P
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> The <SPAN
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> The <SPAN
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CLASS="strong"
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CLASS="strong"
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><B
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><B
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CLASS="EMPHASIS"
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CLASS="EMPHASIS"
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>pshared</B
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>pshared</B
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></SPAN
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></SPAN
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> argument to
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> argument to
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<SPAN
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<SPAN
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CLASS="emphasis"
|
CLASS="emphasis"
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><I
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><I
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CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>sem_init()</I
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>sem_init()</I
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></SPAN
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></SPAN
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> is not implemented,
|
> is not implemented,
|
its value is ignored.
|
its value is ignored.
|
</P
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</P
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></LI
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></LI
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><LI
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><LI
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><P
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><P
|
> Functions <SPAN
|
> Functions <SPAN
|
CLASS="emphasis"
|
CLASS="emphasis"
|
><I
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><I
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>sem_open()</I
|
>sem_open()</I
|
></SPAN
|
></SPAN
|
>,
|
>,
|
<SPAN
|
<SPAN
|
CLASS="emphasis"
|
CLASS="emphasis"
|
><I
|
><I
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>sem_close()</I
|
>sem_close()</I
|
></SPAN
|
></SPAN
|
> and
|
> and
|
<SPAN
|
<SPAN
|
CLASS="emphasis"
|
CLASS="emphasis"
|
><I
|
><I
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>sem_unlink()</I
|
>sem_unlink()</I
|
></SPAN
|
></SPAN
|
> are present but
|
> are present but
|
always return an error (ENOSYS).
|
always return an error (ENOSYS).
|
</P
|
</P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
> The exact priority inversion protocols supported may be
|
> The exact priority inversion protocols supported may be
|
controlled with the
|
controlled with the
|
_POSIX_THREAD_PRIO_INHERIT and
|
_POSIX_THREAD_PRIO_INHERIT and
|
_POSIX_THREAD_PRIO_PROTECT
|
_POSIX_THREAD_PRIO_PROTECT
|
configuration options.
|
configuration options.
|
</P
|
</P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
> {_POSIX_THREAD_PROCESS_SHARED} is
|
> {_POSIX_THREAD_PROCESS_SHARED} is
|
not defined, so the
|
not defined, so the
|
<SPAN
|
<SPAN
|
CLASS="strong"
|
CLASS="strong"
|
><B
|
><B
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>process-shared</B
|
>process-shared</B
|
></SPAN
|
></SPAN
|
> mutex
|
> mutex
|
and condition variable attributes are not supported, and
|
and condition variable attributes are not supported, and
|
neither are the functions
|
neither are the functions
|
<SPAN
|
<SPAN
|
CLASS="emphasis"
|
CLASS="emphasis"
|
><I
|
><I
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>pthread_mutexattr_getpshared()</I
|
>pthread_mutexattr_getpshared()</I
|
></SPAN
|
></SPAN
|
>,
|
>,
|
<SPAN
|
<SPAN
|
CLASS="emphasis"
|
CLASS="emphasis"
|
><I
|
><I
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>pthread_mutexattr_setpshared()</I
|
>pthread_mutexattr_setpshared()</I
|
></SPAN
|
></SPAN
|
>,
|
>,
|
<SPAN
|
<SPAN
|
CLASS="emphasis"
|
CLASS="emphasis"
|
><I
|
><I
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>pthread_condattr_getpshared()</I
|
>pthread_condattr_getpshared()</I
|
></SPAN
|
></SPAN
|
> and
|
> and
|
<SPAN
|
<SPAN
|
CLASS="emphasis"
|
CLASS="emphasis"
|
><I
|
><I
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>pthread_condattr_setpshared()</I
|
>pthread_condattr_setpshared()</I
|
></SPAN
|
></SPAN
|
>.
|
>.
|
</P
|
</P
|
></LI
|
></LI
|
><LI
|
><LI
|
><P
|
><P
|
> Condition variables do not become bound to a particular
|
> Condition variables do not become bound to a particular
|
mutex when
|
mutex when
|
<SPAN
|
<SPAN
|
CLASS="emphasis"
|
CLASS="emphasis"
|
><I
|
><I
|
CLASS="EMPHASIS"
|
CLASS="EMPHASIS"
|
>pthread_cond_wait()</I
|
>pthread_cond_wait()</I
|
></SPAN
|
></SPAN
|
> is
|
> is
|
called. Hence different threads may wait on a condition
|
called. Hence different threads may wait on a condition
|
variable with different mutexes. This is at variance with
|
variable with different mutexes. This is at variance with
|
the standard, which requires a condition variable to
|
the standard, which requires a condition variable to
|
become (dynamically) bound by the first waiter, and
|
become (dynamically) bound by the first waiter, and
|
unbound when the last finishes. However, this difference
|
unbound when the last finishes. However, this difference
|
is largely benign, and the cost of policing this feature
|
is largely benign, and the cost of policing this feature
|
is non-trivial.
|
is non-trivial.
|
</P
|
</P
|
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