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ck_rwlock(3) Library Functions Manual 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, ck_rwlock_write_downgrade —
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/
July 26, 2013.