LIBRARY

Concurrency Kit (libck, -lck)

SYNOPSIS

In ck_rwlock.h

ck_rwlock_t lock = CK_RWLOCK_INITIALIZER;

Ft void Fn ck_rwlock_init ck_rwlock_t *lock Ft void Fn ck_rwlock_write_lock ck_rwlock_t *lock Ft void Fn ck_rwlock_write_unlock ck_rwlock_t *lock Ft bool Fn ck_rwlock_write_trylock ck_rwlock_t *lock Ft bool Fn ck_rwlock_write_downgrade ck_rwlock_t *lock Ft bool Fn ck_rwlock_locked_writer ck_rwlock_t *lock Ft void Fn ck_rwlock_read_lock ck_rwlock_t *lock Ft bool Fn ck_rwlock_read_trylock ck_rwlock_t *lock Ft void Fn ck_rwlock_read_unlock ck_rwlock_t *lock Ft bool Fn ck_rwlock_locked_reader ck_rwlock_t *lock

ck_rwlock_recursive_t lock = CK_RWLOCK_RECURSIVE_INITIALIZER;

Ft void Fn ck_rwlock_recursive_write_lock ck_rwlock_recursive_t *lock unsigned int tid Ft bool Fn ck_rwlock_recursive_write_trylock ck_rwlock_recursive_t *lock unsigned int tid Ft void Fn ck_rwlock_recurisve_write_unlock ck_rwlock_recursive_t *lock Ft void Fn ck_rwlock_recursive_read_lock ck_rwlock_recursive_t *lock Ft bool Fn ck_rwlock_recursive_read_trylock ck_rwlock_recursive_t *lock Ft void Fn 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 Fn 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;
}