ck_swlock(3)

NAME

ck_swlock_init ck_swlock_write_latch ck_swlock_write_unlatch ck_swlock_write_lock ck_swlock_write_unlock ck_swlock_write_trylock ck_swlock_write_downgrade ck_swlock_locked_writer ck_swlock_read_lock ck_swlock_read_trylock ck_swlock_read_unlock ck_swlock_locked_reader – centralized copy-safe write-biased single-writer read-write locks

LIBRARY

Concurrency Kit (libck, -lck)

SYNOPSIS

In ck_swlock.h

ck_swlock_t lock = CK_SWLOCK_INITIALIZER;

Ft void Fn ck_swlock_init ck_swlock_t *lock Ft void Fn ck_swlock_write_lock ck_swlock_t *lock Ft void Fn ck_swlock_write_unlock ck_swlock_t *lock Ft void Fn ck_swlatch_write_latch ck_swlatch_t *latch Ft void Fn ck_swlatch_write_unlatch ck_swlatch_t *latch Ft bool Fn ck_swlock_write_trylock ck_swlock_t *lock Ft bool Fn ck_swlock_write_downgrade ck_swlock_t *lock Ft bool Fn ck_swlock_locked_writer ck_swlock_t *lock Ft void Fn ck_swlock_read_lock ck_swlock_t *lock Ft bool Fn ck_swlock_read_trylock ck_swlock_t *lock Ft void Fn ck_swlock_read_unlock ck_swlock_t *lock Ft bool Fn ck_swlock_locked_reader ck_swlock_t *lock

DESCRIPTION

This is a centralized write-biased single-writer reader-writer lock. It requires half the space that ck_rwlock does and has a low latency fast path. The lock supports latch and unlatch operations that allow it to be used in a copy-safe manner (reader-bits may be over-written safely).

EXAMPLE


#include <ck_swlock.h>
static ck_swlock_t lock = CK_SWLOCK_INITIALIZER;
static void
reader(void)
{
    for (;;) {
        ck_swlock_read_lock(&lock);
        /* Read-side critical section. */
        ck_swlock_read_unlock(&lock);
        if (ck_swlock_read_trylock(&lock) == true) {
            /* Read-side critical section. */
            ck_swlock_read_unlock(&lock);
        }
    }
    return;
}
static void
writer(void)
{
    ck_swlock_t contrived;
    for (;;) {
        ck_swlock_write_lock(&lock);
        /* Write-side critical section. */
        ck_swlock_write_unlock(&lock);
        if (ck_swlock_write_trylock(&lock) == true) {
            /* Write-side critical section. */
            ck_swlock_write_unlock(&lock);
        }
        ck_swlock_write_latch(&lock);
        /* Write-side critical section. */
        /* This is safe to do with-in a latch. */
        contrived = lock;
        lock = contrived;
        ck_swlock_write_unlatch(&lock);
    }
    return;
}