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/