NAME

       MPI_Win_lock_all  -  Starts  an  RMA  access  epoch locking access to all processes in the
       window

SYNTAX

C Syntax

       #include <mpi.h>
       int MPI_Win_lock_all(int assert, MPI_Win win)

Fortran Syntax

       INCLUDE 'mpif.h'
       MPI_WIN_LOCK_ALL(ASSERT, WIN, IERROR)
            INTEGER ASSERT, WIN, IERROR

INPUT PARAMETERS

       assert    Program assertion (integer).

       win       Window object (handle).

OUTPUT PARAMETER

       IERROR    Fortran only: Error status (integer).

DESCRIPTION

       Starts an RMA access epoch to all processes in win, with a lock type  of  MPI_LOCK_SHARED.
       During the epoch, the calling process can access the window memory on all processes in win
       by using RMA operations. A window locked  with  MPI_Win_lock_all  must  be  unlocked  with
       MPI_Win_unlock_all.  This  routine  is  not  collective  — the ALL refers to a lock on all
       members of the group of the window.

       Locks are used to protect accesses to the locked  target  window  effected  by  RMA  calls
       issued  between  the  lock  and unlock call, and to protect local load/store accesses to a
       locked local window executed  between  the  lock  and  unlock  call.   Accesses  that  are
       protected  by  an  exclusive  lock  will  not  be concurrent at the window site with other
       accesses to the same window that are lock protected. Accesses  that  are  protected  by  a
       shared  lock  will  not  be  concurrent  at  the window site with accesses protected by an
       exclusive lock to the same window.

       The assert argument is used to provide assertions on the context of the call that  may  be
       used  for  various  optimizations.  (See  Section 6.4.4 of the MPI-2 Standard.) A value of
       assert = 0 is always valid.

NOTES

       In a client/server environment in which clients connect to a  server  and  create  windows
       that  span  both the client and the server, if a client or server that has obtained a lock
       on such a window and then terminates abnormally, the server or other clients may hang in a
       MPI_Win_lock_all call, failing to notice that the peer MPI job has terminated.

ERRORS

       Almost all MPI routines return an error value; C routines as the value of the function and
       Fortran routines in the last argument.

       Before the error value is returned, the current MPI error handler is called.  By  default,
       this  error  handler aborts the MPI job, except for I/O function errors. The error handler
       may   be   changed   with   MPI_Comm_set_errhandler;   the   predefined   error    handler
       MPI_ERRORS_RETURN may be used to cause error values to be returned. Note that MPI does not
       guarantee that an MPI program can continue past an error.

SEE ALSO

       MPI_Win_unlock_all MPI_Win_lock