ck_rwlock(3)

NAME
ck_rwlock_init, ck_rwlock_write_lock, ck_rwlock_write_unlock, ck_rwlock_write_trylock, ck_rwlock_write_downgrade, ck_rwlock_locked_writer, ck_rwlock_read_lock, ck_rwlock_read_trylock, ck_rwlock_read_unlock, ck_rwlock_locked_reader, ck_rwlock_recursive_write_lock, ck_rwlock_recursive_write_trylock, ck_rwlock_recurisve_write_unlock, ck_rwlock_recursive_read_lock, ck_rwlock_recursive_read_trylock, ck_rwlock_recursive_read_unlock - centralized write-biased reader-writer locks

LIBRARY
Concurrency Kit (libck, -lck)

SYNOPSIS
#include <ck_rwlock.h>

ck_rwlock_t lock = CK_RWLOCK_INITIALIZER;

void
ck_rwlock_init(ck_rwlock_t *lock);
void
ck_rwlock_write_lock(ck_rwlock_t *lock);
void
ck_rwlock_write_unlock(ck_rwlock_t *lock);
bool
ck_rwlock_write_trylock(ck_rwlock_t *lock);
bool
ck_rwlock_write_downgrade(ck_rwlock_t *lock);
bool
ck_rwlock_locked_writer(ck_rwlock_t *lock);
void
ck_rwlock_read_lock(ck_rwlock_t *lock);
bool
ck_rwlock_read_trylock(ck_rwlock_t *lock);
void
ck_rwlock_read_unlock(ck_rwlock_t *lock);
bool
ck_rwlock_locked_reader(ck_rwlock_t *lock);

ck_rwlock_recursive_t lock = CK_RWLOCK_RECURSIVE_INITIALIZER;

void
ck_rwlock_recursive_write_lock(ck_rwlock_recursive_t *lock, unsigned int tid);
bool
ck_rwlock_recursive_write_trylock(ck_rwlock_recursive_t *lock, unsigned int tid);
void
ck_rwlock_recurisve_write_unlock(ck_rwlock_recursive_t *lock);
void
ck_rwlock_recursive_read_lock(ck_rwlock_recursive_t *lock);
bool
ck_rwlock_recursive_read_trylock(ck_rwlock_recursive_t *lock);
void
ck_rwlock_recursive_read_unlock(ck_rwlock_recursive_t *lock);

DESCRIPTION
This is a centralized write-biased reader-writer lock. It requires very little space overhead and has a low latency fast path. Write-side recursion requires usage of ck_rwlock_recursive. Read-side recursion is disallowed. The ck_rwlock_write_downgrade() function degrades the caller's write-side acquisition to a read-side acquisition without forfeit of current critical section.

EXAMPLE

    #include <ck_rwlock.h>

    static ck_rwlock_t lock = CK_RWLOCK_INITIALIZER;

    static void
    reader(void)
    {

    	for (;;) {
    		ck_rwlock_read_lock(&lock);
    		/* Read-side critical section. */
    		ck_rwlock_read_unlock(&lock);

    		if (ck_rwlock_read_trylock(&lock) == true) {
    			/* Read-side critical section. */
    			ck_rwlock_read_unlock(&lock);
    		}
    	}

    	return;
    }

    static void
    writer(void)
    {

    	for (;;) {
    		ck_rwlock_write_lock(&lock);
    		/* Write-side critical section. */
    		ck_rwlock_write_unlock(&lock);

    		if (ck_rwlock_write_trylock(&lock, 1) == true) {
    			/* Write-side critical section. */
    			ck_rwlock_write_unlock(&lock);
    		}
    	}

    	return;
    }

SEE ALSO
ck_brlock(3), ck_elide(3)

Additional information available at http://concurrencykit.org/