PTHREAD_RWLOCK(3) | Library Functions Manual | PTHREAD_RWLOCK(3) |
pthread_rwlock
,
pthread_rwlock_init
,
pthread_rwlock_destroy
,
pthread_rwlock_rdlock
,
pthread_rwlock_timedrdlock
,
pthread_rwlock_tryrdlock
,
pthread_rwlock_wrlock
,
pthread_rwlock_timedwrlock
,
pthread_rwlock_trywrlock
,
pthread_rwlock_unlock
—
#include <pthread.h>
int
pthread_rwlock_init
(pthread_rwlock_t
* restrict lock, const
pthread_rwlockattr_t * restrict attr);
pthread_rwlock_t lock =
PTHREAD_RWLOCK_INITIALIZER
;
int
pthread_rwlock_destroy
(pthread_rwlock_t
*lock);
int
pthread_rwlock_rdlock
(pthread_rwlock_t
*lock);
int
pthread_rwlock_timedrdlock
(pthread_rwlock_t
* restrict lock, const
struct timespec * restrict abstime);
int
pthread_rwlock_tryrdlock
(pthread_rwlock_t
*lock);
int
pthread_rwlock_wrlock
(pthread_rwlock_t
*lock);
int
pthread_rwlock_timedwrlock
(pthread_rwlock_t
* restrict lock, const
struct timespec * restrict abstime);
int
pthread_rwlock_trywrlock
(pthread_rwlock_t
*lock);
int
pthread_rwlock_unlock
(pthread_rwlock_t
*lock);
pthread_rwlock_init
() function is used to initialize
a read/write lock, with attributes specified by attr. If
attr is NULL
, the default
read/write lock attributes are used.
The results of calling
pthread_rwlock_init
() with an already initialized
lock are undefined.
The macro PTHREAD_RWLOCK_INITIALIZER
can
be used to initialize a read/write lock when the allocation can be done
statically, no error checking is required, and the default attributes are
appropriate. The behavior is similar to calling
pthread_rwlock_init
() with
attr specified as NULL
.
The pthread_rwlock_destroy
() function is
used to destroy a read/write lock previously created with
pthread_rwlock_init
().
The pthread_rwlock_rdlock
() function
acquires a read lock on lock provided that
lock is not presently held for writing and no writer
threads are presently blocked on the lock. If the read lock cannot be
immediately acquired, the calling thread blocks until it can acquire the
lock.
The pthread_rwlock_timedrdlock
() performs
the same action, but will not wait beyond abstime to
obtain the lock before returning.
The pthread_rwlock_tryrdlock
() function
performs the same action as pthread_rwlock_rdlock
(),
but does not block if the lock cannot be immediately obtained (i.e., the
lock is held for writing or there are waiting writers).
A thread may hold multiple concurrent read locks. If so,
pthread_rwlock_unlock
() must be called once for each
lock obtained.
The results of acquiring a read lock while the calling thread holds a write lock are undefined.
The pthread_rwlock_wrlock
() function
blocks until a write lock can be acquired against
lock.
The pthread_rwlock_timedwrlock
() performs
the same action, but will not wait beyond abstime to
obtain the lock before returning.
The pthread_rwlock_trywrlock
() function
performs the same action as pthread_rwlock_wrlock
(),
but does not block if the lock cannot be immediately obtained.
The results are undefined if the calling thread already holds the lock at the time the call is made.
The pthread_rwlock_unlock
() function is
used to release the read/write lock previously obtained by
pthread_rwlock_rdlock
(),
pthread_rwlock_wrlock
(),
pthread_rwlock_tryrdlock
(), or
pthread_rwlock_trywrlock
().
pthread_rwlock_init
() function will
return zero. Otherwise an error number will be returned to indicate the error.
If successful, the
pthread_rwlock_destroy
(),
pthread_rwlock_rdlock
(),
pthread_rwlock_timedrdlock
(),
pthread_rwlock_tryrdlock
(),
pthread_rwlock_wrlock
(),
pthread_rwlock_timedwrlock
(),
pthread_rwlock_trywrlock
(), and
pthread_rwlock_unlock
() will return zero. Otherwise
an error number will be returned to indicate the error.
The results are undefined if lock is not held by the calling thread.
pthread_rwlock_init
() function may fail if:
EAGAIN
]EBUSY
]EINVAL
]ENOMEM
]The pthread_rwlock_destroy
() function may
fail if:
EBUSY
]EINVAL
]The pthread_rwlock_tryrdlock
() function
shall fail if:
EBUSY
]The pthread_rwlock_timedrdlock
() function
shall fail if:
ETIMEDOUT
]The pthread_rwlock_rdlock
(),
pthread_rwlock_timedrdlock
(), and
pthread_rwlock_tryrdlock
() functions may fail
if:
EAGAIN
]EDEADLK
]EINVAL
]The pthread_rwlock_trywrlock
() function
shall fail if:
EBUSY
]The pthread_rwlock_timedrdlock
() function
shall fail if:
ETIMEDOUT
]The pthread_rwlock_wrlock
(),
pthread_rwlock_timedwrlock
(), and
pthread_rwlock_trywrlock
() functions may fail
if:
EDEADLK
]EINVAL
]The pthread_rwlock_unlock
() function may
fail if:
PTHREAD_PROCESS_SHARED
attribute is not supported.
July 8, 2010 | NetBSD 9.2 |