PSERIALIZE(9)          NetBSD Kernel Developer's Manual          PSERIALIZE(9)

NAME
     pserialize -- passive serialization mechanism

SYNOPSIS
     #include <sys/pserialize.h>

     pserialize_t
     pserialize_create(void);

     void
     pserialize_destroy(pserialize_t psz);

     int
     pserialize_read_enter(void);

     void
     pserialize_read_exit(int s);

     void
     pserialize_perform(pserialize_t psz);

DESCRIPTION
     Passive serialization is a reader / writer synchronisation mechanism
     designed for lock-less read operations.  The read operations may happen
     from software interrupt at IPL_SOFTCLOCK.

FUNCTIONS
     pserialize_create()
              Allocate a new synchronisation object.

     pserialize_destroy()
              Destroy the synchronisation object.  No synchronisation activity
              should happen at this point.

     pserialize_read_enter()
              Enter the critical path of the reader side.  Returns an IPL
              value, which must be passed to pserialize_read_exit(9).  Pro-
              tected code path is not allowed to block.

     pserialize_read_exit()
              Exit the critical path of the reader side.  Takes the IPL value
              returned by pserialize_read_enter(9).

     pserialize_perform()
              Perform the passive serialization on the writer side.  Passing
              of this function ensures that no readers are in action.  Writers
              must be additionally serialized with a separate mechanism, e.g.
              mutex(9).  Operation blocks and it may only be performed from
              thread context.

EXAMPLES
     Typical code fragment in the writer side:

             mutex_enter(&writer_psz_lock);
             /*
              * Perform the updates (e.g. remove data items from a list).
              */
             ...
             pserialize_perform(object->psz);
             /*
              * At this point it is safe to destroy old data items.
              */
             mutex_exit(&writer_psz_lock);

CODE REFERENCES
     The pserialize is implemented within the file sys/kern/subr_pserialize.c.

SEE ALSO
     membar_ops(3), condvar(9), mutex(9), rwlock(9)

     Hennessy, et al., Passive serialization in a multitasking environment, US
     Patent and Trademark Office, US Patent 4809168, February 28, 1989.

HISTORY
     Passive serialization mechanism first appeared in NetBSD 6.0.

NetBSD 5.0                       July 30, 2011                      NetBSD 5.0