NAME    [Toc]    [Back]

       lock_read - General: Asserts a complex lock with read-only
       access

SYNOPSIS    [Toc]    [Back]

       #include <kern/lock.h>

       void lock_read(
               lock_t lock_structptr );

ARGUMENTS    [Toc]    [Back]

       Specifies a pointer to the complex lock  structure,  lock.
       This is the lock structure associated with the resource on
       which you want to assert a  complex  lock  with  read-only
       access.  The  lock  structure is an opaque data structure;
       that is, its associated members are referenced and manipulated
  by  the operating system and not by the user of the
       complex lock mechanism.

DESCRIPTION    [Toc]    [Back]

       The lock_read routine asserts a lock with read-only access
       for the resource associated with the specified lock structure
 pointer. The lock_read routine allows multiple kernel
       threads to access the resource read-only at the same time.
       When a read lock is asserted, the  protected  resource  is
       guaranteed not to change.

       To  release  a  previously  asserted  read  lock, call the
       lock_done routine.

NOTES    [Toc]    [Back]

       You must call  lock_init  (once  only)  prior  to  calling
       lock_read to initialize the lock structure pointer for the
       resource.  A resource, from  the  kernel  module's  standpoint,
 is data that more than one kernel thread can manipulate.
 You can store the resource in global variables  and
       in data structure members.

RETURN VALUES    [Toc]    [Back]

       None

FILES    [Toc]    [Back]

SEE ALSO
       Routines:        lock_done(9r),        lock_terminate(9r),
       lock_try_read(9r), lock_try_write(9r), lock_write(9r)

       Data Structures: lock(9s)



                                                    lock_read(9r)