NAME

ck_brlock_init, ck_brlock_write_lock, ck_brlock_write_unlock, ck_brlock_write_trylock, ck_brlock_read_register, ck_brlock_read_unregister, ck_brlock_read_lock, ck_brlock_read_trylock, ck_brlock_read_unlock — big-reader locks

LIBRARY

Concurrency Kit (libck, -lck)

SYNOPSIS

#include <ck_brlock.h>

ck_brlock_t brlock = CK_BRLOCK_INITIALIZER;

ck_brlock_reader_t reader = CK_BRLOCK_READER_INITIALIZER;

void
ck_brlock_init(ck_brlock_t *br);

void
ck_brlock_write_lock(ck_brlock_t *br);

void
ck_brlock_write_unlock(ck_brlock_t *br);

bool
ck_brlock_write_trylock(ck_brlock_t *br, unsigned int factor);

void
ck_brlock_read_register(ck_brlock_t *br, ck_brlock_reader_t *reader);

void
ck_brlock_read_unregister(ck_brlock_t *br, ck_brlock_reader_t *reader);

void
ck_brlock_read_lock(ck_brlock_t *br, ck_brlock_reader_t *reader);

bool
ck_brlock_read_trylock(ck_brlock_t *br, ck_brlock_reader_t *reader, unsigned int factor);

void
ck_brlock_read_unlock(ck_brlock_reader_t *reader);

DESCRIPTION

Big reader locks are distributed reader-writer locks with low latency constant time reader acquisition (with respect to number of concurrent readers). On the other hand, writer acquisitions are a relatively expensive O(n) operation. This is a write-biased lock.

EXAMPLE

static ck_brlock_t lock = CK_BRLOCK_INITIALIZER;
static __thread ck_brlock_reader_t reader;

static void
reader(void)
{

	/* Add our thread as a lock participant. */
	ck_brlock_read_register(&lock, &reader);

	for (;;) {
		ck_brlock_read_lock(&lock, &reader);
		/* Read-side critical section. */
		ck_brlock_read_unlock(&reader);

		if (ck_brlock_read_trylock(&lock, &reader, 1) == true) {
			/* Read-side critical section. */
			ck_brlock_read_unlock(&reader);
		}
	}

	return;
}

static void
writer(void)
{

	for (;;) {
		ck_brlock_write_lock(&lock);
		/* Write-side critical section. */
		ck_brlock_write_unlock(&lock);

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

	return;
}

SEE ALSO

ck_bytelock(3), ck_rwlock(3)

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