'\" te
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.TH pthread_rwlock_init 3C "11 Jan 2012" "SunOS 5.11" "Standard C Library Functions"
.SH NAME
pthread_rwlock_init, pthread_rwlock_destroy \- initialize or destroy read-write lock object
.SH SYNOPSIS
.LP
.nf
cc -mt [ \fIflag\fR... ] \fIfile\fR... [ \fIlibrary\fR... ]
#include <pthread.h>

\fBint\fR \fBpthread_rwlock_init\fR(\fBpthread_rwlock_t *restrict\fR \fIrwlock\fR,
     \fBconst pthread_rwlockattr_t *restrict\fR \fIattr\fR);
.fi

.LP
.nf
\fBint\fR \fBpthread_rwlock_destroy\fR(\fBpthread_rwlock_t *\fR\fI*rwlock\fR);
.fi

.LP
.nf
\fBpthread_rwlock_t\fR \fIrwlock\fR=\fBPTHREAD_RWLOCK_INITIALIZER\fR;
.fi

.SH DESCRIPTION
.sp
.LP
The \fBpthread_rwlock_init()\fR function initializes the read-write lock referenced by \fIrwlock\fR with  the attributes referenced by \fIattr\fR.  If \fIattr\fR 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 initialization, the state of the read-write lock  becomes initialized and unlocked.  Results are undefined if  \fBpthread_rwlock_init()\fR is called specifying an already initialized read-write lock.  Results are undefined if a read-write lock is used without first being  initialized.
.sp
.LP
If the  \fBpthread_rwlock_init()\fR function fails, \fIrwlock\fR is not initialized and the contents of  \fIrwlock\fR are undefined.
.sp
.LP
The \fBpthread_rwlock_destroy()\fR function destroys the read-write lock object referenced by \fIrwlock\fR 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 \fBpthread_rwlock_init()\fR. An implementation may cause  \fBpthread_rwlock_destroy()\fR to set the object referenced by \fIrwlock\fR to an invalid value.  Results are undefined if \fBpthread_rwlock_destroy()\fR is called when any thread holds \fIrwlock\fR.  Attempting to destroy an uninitialized  read-write lock results in undefined behaviour.  A destroyed read-write lock object can be re-initialized using \fBpthread_rwlock_init()\fR; the results of otherwise referencing the read-write lock object after it  has been destroyed are undefined.     
.sp
.LP
In cases where default read-write lock attributes are appropriate, the macro  \fBPTHREAD_RWLOCK_INITIALIZER\fR can be used to initialize read-write locks that are statically allocated.  The effect is equivalent to dynamic initialization by a call to  \fBpthread_rwlock_init()\fR with the parameter \fIattr\fR specified as NULL, except that no error  checks are performed. 
.SH RETURN VALUES
.sp
.LP
If successful, the  \fBpthread_rwlock_init()\fR and  \fBpthread_rwlock_destroy()\fR functions return  \fB0\fR. Otherwise, an  error number is returned to indicate the error. 
.SH ERRORS
.sp
.LP
The \fBpthread_rwlock_init()\fR and  \fBpthread_rwlock_destroy()\fR functions will fail if:
.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
.rt  
The value specified by \fIattr\fR is invalid.
.RE

.sp
.ne 2
.mk
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
.rt  
The value specified by \fIrwlock\fR is invalid.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
tab() box;
cw(2.75i) |cw(2.75i) 
lw(2.75i) |lw(2.75i) 
.
ATTRIBUTE TYPEATTRIBUTE VALUE
_
Interface StabilityCommitted
_
MT-LevelMT-Safe
_
StandardSee \fBstandards\fR(5).
.TE

.SH SEE ALSO
.sp
.LP
\fBpthread_rwlock_rdlock\fR(3C), \fBpthread_rwlock_unlock\fR(3C), \fBpthread_rwlock_wrlock\fR(3C), \fBpthread_rwlockattr_init\fR(3C), \fBattributes\fR(5), \fBstandards\fR(5)