Manual Pages


ck_spinlock(3)           BSD Library Functions Manual           ck_spinlock(3)

NAME
     ck_spinlock_init, ck_spinlock_lock, ck_spinlock_unlock,
     ck_spinlock_locked, ck_spinlock_trylock, ck_spinlock_anderson_init,
     ck_spinlock_anderson_locked, ck_spinlock_anderson_lock,
     ck_spinlock_anderson_unlock, ck_spinlock_cas_init,
     ck_spinlock_cas_locked, ck_spinlock_cas_lock, ck_spinlock_cas_lock_eb,
     ck_spinlock_cas_trylock, ck_spinlock_cas_unlock, ck_spinlock_clh_init,
     ck_spinlock_clh_locked, ck_spinlock_clh_lock, ck_spinlock_clh_unlock,
     ck_spinlock_dec_init, ck_spinlock_dec_locked, ck_spinlock_dec_lock,
     ck_spinlock_dec_lock_eb, ck_spinlock_dec_trylock, ck_spinlock_dec_unlock,
     ck_spinlock_fas_init, ck_spinlock_fas_lock, ck_spinlock_fas_lock_eb,
     ck_spinlock_fas_locked, ck_spinlock_fas_trylock, ck_spinlock_fas_unlock,
     ck_spinlock_hclh_init, ck_spinlock_hclh_locked, ck_spinlock_hclh_lock,
     ck_spinlock_hclh_unlock, ck_spinlock_mcs_init, ck_spinlock_mcs_locked,
     ck_spinlock_mcs_lock, ck_spinlock_mcs_trylock, ck_spinlock_mcs_unlock,
     ck_spinlock_ticket_init, ck_spinlock_ticket_locked,
     ck_spinlock_ticket_lock, ck_spinlock_ticket_lock_pb,
     ck_spinlock_ticket_trylock, ck_spinlock_ticket_unlock -- spinlock imple-
     mentations

LIBRARY
     Concurrency Kit (libck, -lck)

SYNOPSIS
     #include <ck_spinlock.h>

     ck_spinlock_t spinlock = CK_SPINLOCK_INITIALIZER;

     void
     ck_spinlock_init(ck_spinlock_t *lock);

     void
     ck_spinlock_lock(ck_spinlock_t *lock);

     void
     ck_spinlock_unlock(ck_spinlock_t *lock);

     bool
     ck_spinlock_locked(ck_spinlock_t *lock);

     bool
     ck_spinlock_trylock(ck_spinlock_t *lock);

     void
     ck_spinlock_anderson_init(ck_spinlock_anderson_t *lock,
         ck_spinlock_anderson_thread_t *slots, unsigned int count);

     bool
     ck_spinlock_anderson_locked(ck_spinlock_anderson_t *lock);

     void
     ck_spinlock_anderson_lock(ck_spinlock_anderson_t *lock,
         ck_spinlock_anderson_thread_t **slot);

     void
     ck_spinlock_anderson_unlock(ck_spinlock_anderson_t *lock,
         ck_spinlock_anderson_thread_t *slot);

     ck_spinlock_cas_t spinlock = CK_SPINLOCK_CAS_INITIALIZER;

     void
     ck_spinlock_cas_init(ck_spinlock_cas_t *lock);

     bool
     ck_spinlock_cas_locked(ck_spinlock_cas_t *lock);

     void
     ck_spinlock_cas_lock(ck_spinlock_cas_t *lock);

     void
     ck_spinlock_cas_lock_eb(ck_spinlock_cas_t *lock);

     bool
     ck_spinlock_cas_trylock(ck_spinlock_cas_t *lock);

     void
     ck_spinlock_cas_unlock(ck_spinlock_cas_t *lock);

     void
     ck_spinlock_clh_init(ck_spinlock_clh_t **lock,
         ck_spinlock_clh_t *unowned);

     bool
     ck_spinlock_clh_locked(ck_spinlock_clh_t **lock);

     void
     ck_spinlock_clh_lock(ck_spinlock_clh_t **lock, ck_spinlock_clh_t *node);

     void
     ck_spinlock_clh_unlock(ck_spinlock_clh_t **node);

     ck_spinlock_dec_t spinlock = CK_SPINLOCK_DEC_INITIALIZER;

     void
     ck_spinlock_dec_init(ck_spinlock_dec_t *lock);

     bool
     ck_spinlock_dec_locked(ck_spinlock_dec_t *lock);

     void
     ck_spinlock_dec_lock(ck_spinlock_dec_t *lock);

     void
     ck_spinlock_dec_lock_eb(ck_spinlock_dec_t *lock);

     bool
     ck_spinlock_dec_trylock(ck_spinlock_dec_t *lock);

     void
     ck_spinlock_dec_unlock(ck_spinlock_dec_t *lock);

     ck_spinlock_fas_t spinlock = CK_SPINLOCK_FAS_INITIALIZER;

     void
     ck_spinlock_fas_init(ck_spinlock_fas_t *lock);

     void
     ck_spinlock_fas_lock(ck_spinlock_fas_t *lock);

     void
     ck_spinlock_fas_lock_eb(ck_spinlock_fas_t *lock);

     bool
     ck_spinlock_fas_locked(ck_spinlock_fas_t *lock);

     bool
     ck_spinlock_fas_trylock(ck_spinlock_fas_t *lock);

     void
     ck_spinlock_fas_unlock(ck_spinlock_fas_t *lock);

     void
     ck_spinlock_hclh_init(ck_spinlock_hclh_t **lock,
         ck_spinlock_hclh_t *unowned);

     bool
     ck_spinlock_hclh_locked(ck_spinlock_hclh_t **lock);

     void
     ck_spinlock_hclh_lock(ck_spinlock_hclh_t **lock,
         ck_spinlock_hclh_t *node);

     void
     ck_spinlock_hclh_unlock(ck_spinlock_hclh_t **node);

     ck_spinlock_mcs_t spinlock = CK_SPINLOCK_MCS_INITIALIZER;

     void
     ck_spinlock_mcs_init(ck_spinlock_mcs_t **lock);

     bool
     ck_spinlock_mcs_locked(ck_spinlock_mcs_t **lock);

     void
     ck_spinlock_mcs_lock(ck_spinlock_mcs_t **lock, ck_spinlock_mcs_t *node);

     bool
     ck_spinlock_mcs_trylock(ck_spinlock_mcs_t **lock,
         ck_spinlock_mcs_t *node);

     void
     ck_spinlock_mcs_unlock(ck_spinlock_mcs_t **lock,
         ck_spinlock_mcs_t *node);

     ck_spinlock_ticket_t spinlock = CK_SPINLOCK_TICKET_INITIALIZER;

     void
     ck_spinlock_ticket_init(ck_spinlock_ticket_t *lock);

     bool
     ck_spinlock_ticket_locked(ck_spinlock_ticket_t *lock);

     void
     ck_spinlock_ticket_lock(ck_spinlock_ticket_t *lock);

     void
     ck_spinlock_ticket_lock_pb(ck_spinlock_ticket_t *lock,
         unsigned int period);

     bool
     ck_spinlock_ticket_trylock(ck_spinlock_ticket_t *lock);

     void
     ck_spinlock_ticket_unlock(ck_spinlock_ticket_t *lock);

DESCRIPTION
     A family of busy-wait spinlock implementations. The ck_spinlock_t imple-
     mentation is simply a wrapper around the fetch-and-swap (ck_spin-
     lock_fas_t) implementation. The table below provides a summary of the
     current implementations.

     |            Namespace | Algorithm                   | Type          | Restrictions            | Fair   |
     '----------------------|-----------------------------|---------------|-------------------------|--------'
       ck_spinlock_anderson   Anderson                      Array           Fixed number of threads   Yes
            ck_spinlock_cas   Compare-and-Swap              Centralized     None                      No
            ck_spinlock_clh   Craig, Landin and Hagersten   Queue           Lifetime requirements     Yes
            ck_spinlock_dec   Decrement (Linux kernel)      Centralized     UINT_MAX concurrency      No
            ck_spinlock_fas   Fetch-and-store               Centralized     None                      No
            ck_spinlock_hclh  Hierarchical CLH              Queue           Lifetime requirements     Yes *
            ck_spinlock_mcs   Mellor-Crummey and Scott      Queue           None                      Yes
         ck_spinlock_ticket   Ticket                        Centralized     None                      Yes

     * Hierarchical CLH only offers weak fairness for threads accross cluster
     nodes.

     If contention is low and there is no hard requirement for starvation-
     freedom then a centralized greedy (unfair) spinlock is recommended. If
     contention is high and there is no requirement for starvation-freedom
     then a centralized greedy spinlock is recommended to be used with an
     exponential backoff mechanism. If contention is generally low and there
     is a hard requirement for starvation-freedom then the ticket lock is rec-
     ommended. If contention is high and there is a hard requirement for star-
     vation-freedom then the Craig and Landin and Hagersten queue spinlock is
     recommended unless stack allocation is necessary or NUMA factor is high,
     in which case the Mellor-Crummey and Scott spinlock is recommended. If
     you cannot afford O(n) space-usage from array or queue spinlocks but
     still require fairness under high contention then the ticket lock with
     proportional back-off is recommended.  If NUMA factor is high but prefer
     a greedy lock, then please see ck_cohort(3).

EXAMPLE
           #include <ck_spinlock.h>
           #include <stdbool.h>

           /*
            * Alternatively, the mutex may be initialized at run-time with
            * ck_spinlock_init(&mutex).
            */
           ck_spinlock_t mutex = CK_SPINLOCK_INITIALIZER;

           void
           example(void)
           {

                   ck_spinlock_lock(&mutex);
                   /*
                    * Critical section.
                    */
                   ck_spinlock_unlock(&mutex);

                   ck_spinlock_lock_eb(&mutex);
                   /*
                    * Critical section.
                    */
                   ck_spinlock_unlock(&mutex);

                   if (ck_spinlock_trylock(&mutex) == true) {
                           /*
                            * Critical section.
                            */
                           ck_spinlock_unlock(&mutex);
                   }
           }

SEE ALSO
     ck_cohort(3), ck_elide(3)

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

                                July 26, 2013.