Fix man page for MPI_Win_attach

The text seems to have been copied from MPI_Win_allocate and was
thus incorrect.

Signed-off-by: Joseph Schuchart <schuchart@icl.utk.edu>

Author: devreal

ompi/mpi/man/man3/MPI_Win_attach.3in

@@ -5,7 +5,7 @@
 .\" $COPYRIGHT$
 .TH MPI_Win_attach 3 "#OMPI_DATE#" "#PACKAGE_VERSION#" "#PACKAGE_NAME#"
 .SH NAME
-\fBMPI_Win_attach, MPI_Win_detach\fP \- One-sided MPI call that attach / detach a window object for RMA operations.
+\fBMPI_Win_attach, MPI_Win_detach\fP \- One-sided MPI call that attaches / detaches a memory region to / from a window object for RMA operations.
 
 .SH SYNTAX
 .ft R
@@ -68,10 +68,14 @@ Fortran only: Error status (integer).
 
 .SH DESCRIPTION
 .ft R
-MPI_Win_attach is a one-sided MPI communication collective call executed by all processes in the group of \fIcomm\fP. It returns a window object that can be used by these processes to perform RMA operations. Each process specifies a window of existing memory that it exposes to RMA accesses by the processes in the group of \fIcomm\fP. The window consists of \fIsize\fP bytes, starting at address \fIbase\fP. A process may elect to expose no memory by specifying \fIsize\fP = 0.
+MPI_Win_attach is a one-sided MPI communication call used to attach a memory region of \fIsize\fP bytes starting at address \fIbase\fP to a window for RMA access. The window \fIwin\fP must have been created using
+.IR MPI_Win_create_dynamic .
+Multiple non-overlapping memory regions may be attached to the same dynamic window. Attaching overlapping memory regions to the same dynamic window is erroneous.
 .sp
 If the \fIbase\fP value used by MPI_Win_attach was allocated by MPI_Alloc_mem, the size of the window can be no larger than the value set by the MPI_ALLOC_MEM function.
 .sp
+.sp
+MPI_Win_detach can be used to detach a previously attached memory region from \fIwin\fP. The memory address \fIbase\fP and \fIwin\fP must match arguments passed to a previous call to MPI_Win_attach.
 
 .SH NOTES
 Use memory allocated by MPI_Alloc_mem to guarantee properly aligned window boundaries (such as word, double-word, cache line, page frame, and so on).
@@ -86,4 +90,3 @@ 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.
 
 
-