pthread_rwlock_init(3c) [sunos man page]

pthread_rwlock_init(3C) 												   pthread_rwlock_init(3C)

NAME

       pthread_rwlock_init, pthread_rwlock_destroy - initialize or destroy read-write lock object

SYNOPSIS

       cc -mt [ flag... ] file... -lpthread [ library... ]
       #include <pthread.h>

       int pthread_rwlock_init(pthread_rwlock_t *restrict rwlock, const pthread_rwlockattr_t *restrict attr);

       int pthread_rwlock_destroy(pthread_rwlock_t **rwlock);
       pthread_rwlock_t rwlock=PTHREAD_RWLOCK_INITIALIZER;

       The  pthread_rwlock_init()  function initializes the read-write lock referenced by rwlock with  the attributes referenced by attr.  If attr
       is NULL, the default  read-write lock attributes are used; the effect is the same as  passing the address  of  a  default  read-write  lock
       attributes  object.  Once initialized, the lock can be used any	number of times without being re-initialized.  Upon successful initializa-
       tion, the state of the read-write lock  becomes initialized and unlocked.  Results are undefined if  pthread_rwlock_init() is called speci-
       fying an already initialized read-write lock.  Results are undefined if a read-write lock is used without first being  initialized.

       If the  pthread_rwlock_init() function fails, rwlock is not initialized and the contents of  rwlock are undefined.

       The  pthread_rwlock_destroy()  function	destroys  the  read-write lock object referenced by rwlock and	releases any resources used by the
       lock.  The effect of subsequent use of the lock is undefined until the lock  is re-initialized by another call to pthread_rwlock_init(). An
       implementation  may  cause   pthread_rwlock_destroy() to set the object referenced by rwlock to an invalid value.  Results are undefined if
       pthread_rwlock_destroy() is called when any thread holds rwlock.  Attempting to destroy an uninitialized  read-write lock results in  unde-
       fined  behaviour.  A destroyed read-write lock object can be re-initialized using pthread_rwlock_init(); the results of otherwise referenc-
       ing the read-write lock object after it	has been destroyed are undefined.

       In cases where default read-write lock attributes are appropriate, the macro  PTHREAD_RWLOCK_INITIALIZER can be used  to  initialize  read-
       write locks that are statically allocated.  The effect is equivalent to dynamic initialization by a call to  pthread_rwlock_init() with the
       parameter attr specified as NULL, except that no error  checks are performed.

       If successful, the  pthread_rwlock_init() and  pthread_rwlock_destroy() functions return  0. Otherwise, an  error  number  is  returned	to
       indicate the error.

       The pthread_rwlock_init() and  pthread_rwlock_destroy() functions will fail if:

       EINVAL	       The value specified by attr is invalid.

       EINVAL	       The value specified by rwlock is invalid.

       See attributes(5) for descriptions of the following attributes:

       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Standard			   |
       +-----------------------------+-----------------------------+
       |MT-Level		     |MT-Safe			   |
       +-----------------------------+-----------------------------+

       pthread_rwlock_rdlock(3C), pthread_rwlock_unlock(3C), pthread_rwlock_wrlock(3C), pthread_rwlockattr_init(3C), attributes(5), standards(5)

								    23 mar 2005 					   pthread_rwlock_init(3C)

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pthread_rwlock_init(3)					     Library Functions Manual					    pthread_rwlock_init(3)

NAME

       pthread_rwlock_init - Initializes a read-write lock object.

LIBRARY

       DECthreads POSIX 1003.1c Library (libpthread.so)

SYNOPSIS

       #include <pthread.h>

       int   pthread_rwlock_init(
			     pthread_rwlock_t		  *rwlock,
			     const pthread_rwlockattr_t   *attr);

PARAMETERS

       Read-write  lock object to be initialized.  Read-write lock attributes object that defines the characteristics of the read-write lock to be
       initialized.

DESCRIPTION

       This routine initializes a read-write lock object with the attributes specified by the read-write lock attributes object specified in attr.
       A  read-write  lock  is	a synchronization object that serializes access to shared information that needs to be read frequently and written
       only occasionally.  A thread can acquire a read-write lock for shared read access or for exclusive write access.

       Upon successful completion of this routine, the read-write lock is initialized and set to the unlocked state.  If attr is set to NULL,  the
       default	read-write lock attributes are used; the effect is the same as passing the address of a default read-write lock attributes object.
       Once initialized, the lock can be used any number of times without being reinitialized.

       Results of calling this routine are undefined if attr specifies an already initialized read-write lock or if rwlock is used  without  first
       being initialized.

       If this routine returns unsuccessfully, rwlock is not initialized and the contents of rwlock are undefined.

       A  read-write  lock  is	a resource of the process, not part of any particular thread.  A read-write lock is neither destroyed not unlocked
       automatically when any thread exits.  Because read-write locks are shared, they may be allocated in heap or static memory,  but	not  on  a
       stack.

       In  cases where default read-write lock attributes are appropriate, you may use the PTHREAD_RWLOCK_INITIALIZER macro to statically initial-
       ize the lock object without calling this routine.  The effect is equivalent to dynamic initialization by a call to pthread_rwlock_init with
       attr  specified	as  NULL,  except  that no error checks are performed. Statically initialized read-write locks need not be destroyed using
       pthread_rwlock_destroy.

       Use the PTHREAD_RWLOCK_INITIALIZER macro as follows:

       pthread_rwlock_t  rwlock = PTHREAD_RWLOCK_INITIALIZER;

RETURN VALUES

       If an error condition occurs, this routine returns an integer value indicating the type of error.  Possible return values are  as  follows:
       Successful  completion.	 The  system  lacks the necessary resources to initialize the read-write lock.	The implementation has detected an
       attempt to reinitialize the read-write lock (a previously initialized, but not yet destroyed read-write lock object).  The value  specified
       by  attr  is  not a valid attributes block.  Insufficient memory exists to initialize the read-write lock.  The caller does not have privi-
       leges to perform this operation.

ERRORS

       None

RELATED INFORMATION

       Functions: pthread_rwlock_destroy(3)

       Manuals: Guide to DECthreads and Programmer's Guide

       delim off

															    pthread_rwlock_init(3)

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pthread_rwlock_init(3c) [sunos man page]

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