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<H1 id="MPI_Win_lock_all">MPI_Win_lock_all</H1>
Begin an RMA access epoch at all processes on the given window.
<H2>Synopsis</H2>
<PRE>
int MPI_Win_lock_all(int assert, MPI_Win win)
</PRE>
<P>
Starts an RMA access epoch to all processes in win, with a lock type of
<tt>MPI_Lock_shared</tt>. During the epoch, the calling process can access the window
memory on all processes in win by using RMA operations. A window locked with
<tt>MPI_Win_lock_all</tt> must be unlocked with <tt>MPI_Win_unlock_all</tt>. This routine is not
collective -- the ALL refers to a lock on all members of the group of the
window.
<P>
<H2>Input Parameters</H2>
<DL>
<DT><B>assert </B> <DD> Used to optimize this call; zero may be used as a default.
See notes. (integer)
<DT><B>win </B> <DD> window object (handle)
</DL>
<P>
<H2>Notes</H2>
<P>
This call is not collective.
<P>
The <tt>assert</tt> argument is used to indicate special conditions for the fence that
an implementation may use to optimize the <tt>MPI_Win_lock_all</tt> operation. The
value zero is always correct. Other assertion values may be or'ed together.
Assertions that are valid for <tt>MPI_Win_lock_all</tt> are:
<P>
<DL>
<DT><B><tt>MPI_MODE_NOCHECK</tt> </B> <DD> No other process holds, or will attempt to acquire a
conflicting lock, while the caller holds the window lock. This is useful
when mutual exclusion is achieved by other means, but the coherence
operations that may be attached to the lock and unlock calls are still
required.
</DL>
<P>
There may be additional overheads associated with using <tt>MPI_Win_lock</tt> and
<tt>MPI_Win_lock_all</tt> concurrently on the same window. These overheads could be
avoided by specifying the assertion <tt>MPI_MODE_NOCHECK</tt> when possible
<P>
<H2>Thread and Interrupt Safety</H2>
<P>
This routine is thread-safe. This means that this routine may be
safely used by multiple threads without the need for any user-provided
thread locks. However, the routine is not interrupt safe. Typically,
this is due to the use of memory allocation routines such as <tt>malloc
</tt>or other non-MPICH runtime routines that are themselves not interrupt-safe.
<P>
<H2>Notes for Fortran</H2>
All MPI routines in Fortran (except for <tt>MPI_WTIME</tt> and <tt>MPI_WTICK</tt>) have
an additional argument <tt>ierr</tt> at the end of the argument list. <tt>ierr
</tt>is an integer and has the same meaning as the return value of the routine
in C. In Fortran, MPI routines are subroutines, and are invoked with the
<tt>call</tt> statement.
<P>
All MPI objects (e.g., <tt>MPI_Datatype</tt>, <tt>MPI_Comm</tt>) are of type <tt>INTEGER
</tt>in Fortran.
<P>
<H2>Errors</H2>
<P>
All MPI routines (except <tt>MPI_Wtime</tt> and <tt>MPI_Wtick</tt>) return an error value;
C routines as the value of the function and Fortran routines in the last
argument. Before the value is returned, the current MPI error handler is
called. By default, this error handler aborts the MPI job. The error handler
may be changed with <tt>MPI_Comm_set_errhandler</tt> (for communicators),
<tt>MPI_File_set_errhandler</tt> (for files), and <tt>MPI_Win_set_errhandler</tt> (for
RMA windows). The MPI-1 routine <tt>MPI_Errhandler_set</tt> may be used but
its use is deprecated. The predefined error handler
<tt>MPI_ERRORS_RETURN</tt> may be used to cause error values to be returned.
Note that MPI does <em>not</em> guarentee that an MPI program can continue past
an error; however, MPI implementations will attempt to continue whenever
possible.
<P>
<DL>
<DT><B>MPI_SUCCESS </B> <DD> No error; MPI routine completed successfully.
</DL>
<DL>
<DT><B>MPI_ERR_RANK </B> <DD> Invalid source or destination rank. Ranks must be between
zero and the size of the communicator minus one; ranks in a receive
(<tt>MPI_Recv</tt>, <tt>MPI_Irecv</tt>, <tt>MPI_Sendrecv</tt>, etc.) may also be <tt>MPI_ANY_SOURCE</tt>.
</DL>
<DL>
<DT><B>MPI_ERR_WIN </B> <DD> Invalid MPI window object
</DL>
<DL>
<DT><B>MPI_ERR_OTHER </B> <DD> Other error; use <tt>MPI_Error_string</tt> to get more information
about this error code.
</DL>
<P>
<H2>See Also</H2>
MPI_Win_unlock_all
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