pthread_rwlock.h File Reference

Implementation of a fair, POSIX conforming reader/writer lock. More...

Detailed Description

Implementation of a fair, POSIX conforming reader/writer lock.

Note

Do not include this header file directly, but pthread.h.

Definition in file pthread_rwlock.h.

#include "priority_queue.h"
#include "thread.h"
#include <errno.h>
#include <stdbool.h>

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Go to the source code of this file.

Data Structures
struct	pthread_rwlock_t
	A fair reader writer lock. More...
struct	__pthread_rwlock_waiter_node_t
	Internal structure that stores one waiting thread. More...
int	pthread_rwlock_init (pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr)
	Initialize a reader/writer lock.
int	pthread_rwlock_destroy (pthread_rwlock_t *rwlock)
	Destroy a reader/writer lock.
int	pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
	Lock a reader/writer lock for reading.
int	pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
	Try to lock a reader/writer lock for reader.
int	pthread_rwlock_timedrdlock (pthread_rwlock_t *rwlock, const struct timespec *abstime)
	Try to acquire a read lock in a given timeframe.
int	pthread_rwlock_wrlock (pthread_rwlock_t *rwlock)
	Lock a reader/writer lock for writing.
int	pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock)
	Try to lock a reader/writer lock for writing.
int	pthread_rwlock_timedwrlock (pthread_rwlock_t *rwlock, const struct timespec *abstime)
	Try to acquire a write lock in a given timeframe.
int	pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
	Unlock the reader/writer lock.
bool	__pthread_rwlock_blocked_readingly (const pthread_rwlock_t *rwlock)
	Internal function to determine of the lock can be acquired for reading.
bool	__pthread_rwlock_blocked_writingly (const pthread_rwlock_t *rwlock)
	Internal function to determine of the lock can be acquired for writing.

Function Documentation

__pthread_rwlock_blocked_readingly()

bool __pthread_rwlock_blocked_readingly

(

const pthread_rwlock_t *

rwlock

)

Internal function to determine of the lock can be acquired for reading.

Parameters

[in]

rwlock

Lock to query.

Returns

false if locking for reading is possible without blocking.

__pthread_rwlock_blocked_writingly()

bool __pthread_rwlock_blocked_writingly

(

const pthread_rwlock_t *

rwlock

)

Internal function to determine of the lock can be acquired for writing.

Parameters

[in]

rwlock

Lock to query.

Returns

false if locking for writing is possible without blocking.

pthread_rwlock_destroy()

int pthread_rwlock_destroy

(

pthread_rwlock_t *

rwlock

)

Destroy a reader/writer lock.

This is a no-op. Destroying a reader/writer lock while a thread holds it, or there are threads waiting for it causes undefined behavior. Datum must be reinitialized before using it again.

Parameters

[in]

rwlock

Lock to destroy.

Returns

0 on success. EINVAL if rwlock == NULL. EBUSY if the lock was in use.

pthread_rwlock_init()

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

Initialize a reader/writer lock.

A zeroed out datum is initialized.

Parameters

[in,out]	rwlock	Lock to initialize.
[in]	attr	Unused.

Returns

0 on success. EINVAL if rwlock == NULL.

pthread_rwlock_rdlock()

int pthread_rwlock_rdlock

(

pthread_rwlock_t *

rwlock

)

Lock a reader/writer lock for reading.

This function may block.

Parameters

[in]

rwlock

Lock to acquire for reading.

Returns

0 if the lock could be acquired. EINVAL if rwlock == NULL.

pthread_rwlock_timedrdlock()

int pthread_rwlock_timedrdlock	(	pthread_rwlock_t *	rwlock,
		const struct timespec *	abstime
	)

Try to acquire a read lock in a given timeframe.

Parameters

[in]	rwlock	Lock to acquire for reading.
[in]	abstime	Maximum timestamp when to wakeup, absolute.

Returns

0 if the lock could be acquired. EDEADLK if the lock could not be acquired in the given timeframe. EINVAL if rwlock == NULL.

pthread_rwlock_timedwrlock()

int pthread_rwlock_timedwrlock	(	pthread_rwlock_t *	rwlock,
		const struct timespec *	abstime
	)

Try to acquire a write lock in a given timeframe.

Parameters

[in]	rwlock	Lock to acquire for writing.
[in]	abstime	Maximum timestamp when to wakeup, absolute.

Returns

0 if the lock could be acquired. EDEADLK if the lock could not be acquired in the given timeframe. EINVAL if rwlock == NULL.

pthread_rwlock_tryrdlock()

int pthread_rwlock_tryrdlock

(

pthread_rwlock_t *

rwlock

)

Try to lock a reader/writer lock for reader.

This function won't block.

Parameters

[in]

rwlock

Lock to acquire for reading.

Returns

0 if the lock could be acquired. EBUSY if acquiring the lock cannot be done without blocking. EINVAL if rwlock == NULL.

pthread_rwlock_trywrlock()

int pthread_rwlock_trywrlock

(

pthread_rwlock_t *

rwlock

)

Try to lock a reader/writer lock for writing.

This function won't block.

Parameters

[in]

rwlock

Lock to acquire for writing.

Returns

0 if the lock could be acquired. EBUSY if acquiring the lock cannot be done without blocking. EINVAL if rwlock == NULL.

pthread_rwlock_unlock()

int pthread_rwlock_unlock

(

pthread_rwlock_t *

rwlock

)

Unlock the reader/writer lock.

Must only be used if the lock is currently held. You may release the lock out of another thread, but the lock, operate, unlock logic must not be broken.

Parameters

[in]

rwlock

Lock to release

Returns

0 on success. EPERM if the lock was not held for any operation. EINVAL if rwlock == NULL.

pthread_rwlock_wrlock()

int pthread_rwlock_wrlock

(

pthread_rwlock_t *

rwlock

)

Lock a reader/writer lock for writing.

This function may block.

Parameters

[in]

rwlock

Lock to acquire for writing.

Returns

0 if the lock could be acquired. EINVAL if rwlock == NULL.