RW_ALLOC(D3)

NAME
     RW_ALLOC, RW_INIT - reader/writer lock initialization

SYNOPSIS
     #include <sys/types.h>
     #include <sys/kmem.h>
     #include <sys/ksynch.h>
     #include <sys/ddi.h>
     sleep_t *RW_ALLOC(char *name, int flag);

     void RW_INIT(rwlock_t *lockp, char *name);

   Arguments
     lockp     Pointer to uninitialized reader/writer lock.

     name      Name applied to reader/writer lock when metering locks are
               installed.

     flag      Specifies whether the caller is willing to sleep waiting for
               memory.

DESCRIPTION
     RW_ALLOC dynamically allocates and initializes an instance of a
     reader/writer lock.  RW_INIT initializes an instance of a reader/writer
     lock.  The lock is initialized to the unlocked state.

     If flag is set to KM_SLEEP, the caller will sleep if necessary until
     sufficient memory is available.  If flag is set to KM_NOSLEEP, the caller
     will not sleep, but RW_ALLOC will return NULL if sufficient memory is not
     immediately available.

   Return Values
     Upon successful completion, RW_ALLOC returns a pointer to the newly
     allocated lock.  If KM_NOSLEEP is specified and sufficient memory is not
     immediately available, RW_ALLOC returns a NULL pointer.

USAGE
   Level
     Base or Initialization.

   Synchronization Constraints
     May sleep if flag is set to KM_SLEEP.

     Driver-defined basic locks and sleeping locks may be held across calls to
     this function if flag is KM_NOSLEEP but may not be held if flag is
     KM_SLEEP.

     Driver-defined sleeping locks may be held across calls to this function
     regardless of the value of flag.
REFERENCES
     RW_DEALLOC(D3), RW_DESTROY(D3), RW_RDLOCK(D3), RW_WRLOCK(D3),
     RW_TRYRDLOCK(D3), RW_TRYWRLOCK(D3), RW_UNLOCK(D3)