DragonFly On-Line Manual Pages

ck_swlock(3)          DragonFly Library Functions Manual          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
     #include <ck_swlock.h>

     ck_swlock_t lock = CK_SWLOCK_INITIALIZER;

     void
     ck_swlock_init(ck_swlock_t *lock);

     void
     ck_swlock_write_lock(ck_swlock_t *lock);

     void
     ck_swlock_write_unlock(ck_swlock_t *lock);

     void
     ck_swlatch_write_latch(ck_swlatch_t *latch);

     void
     ck_swlatch_write_unlatch(ck_swlatch_t *latch);

     bool
     ck_swlock_write_trylock(ck_swlock_t *lock);

     bool
     ck_swlock_write_downgrade(ck_swlock_t *lock);

     bool
     ck_swlock_locked_writer(ck_swlock_t *lock);

     void
     ck_swlock_read_lock(ck_swlock_t *lock);

     bool
     ck_swlock_read_trylock(ck_swlock_t *lock);

     void
     ck_swlock_read_unlock(ck_swlock_t *lock);

     bool
     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;
           }

SEE ALSO
     ck_brlock(3), ck_elide(3), ck_pflock(3), ck_rwlock(3), ck_tflock(3)

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

                                April 22, 2014.