03-25-2004
In other words, the children are doing nothing while waiting for the parent's notification. I agree that you will need a semaphore then, because the order in which signals are handled cannot be enforced in a reliable manner without resorting to changing scheduling policies, which is definitely not justified in this case.
I would probably do this:
Have each child install a signal handler for SIGUSR1, without restarting interrupted system calls. Have a loop calling pause() for the desired number of times the PID shall be written. After the parent has signaled the current child, it goes to sleep on a semaphore. After the child has written its PID to the file, it awakes the parent by incrementing the semaphore and calls pause() again. The parent goes on to signal the next child, and so on. Good luck
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LEARN ABOUT ULTRIX
xtunmanagechildren
XtManageChildren(3Xt) MIT X11R4 XtManageChildren(3Xt)
Name
XtManageChildren, XtManageChild, XtUnmanageChildren, XtUnmanageChild - manage and unmanage children
Syntax
typedef Widget *WidgetList;
void XtManageChildren(children, num_children)
WidgetList children;
Cardinal num_children;
void XtManageChild(child)
Widget child;
void XtUnmanageChildren(children, num_children)
WidgetList children;
Cardinal num_children;
void XtUnmanageChild(child)
Widget child;
Arguments
child Specifies the child.
children Specifies a list of child widgets.
num_children
Specifies the number of children.
Description
The function performs the following:
o Issues an error if the children do not all have the same parent or if the parent is not a subclass of
o Returns immediately if the common parent is being destroyed; otherwise, for each unique child on the list, ignores the child if it
already is managed or is being destroyed and marks it if not.
o If the parent is realized and after all children have been marked, it makes some of the newly managed children viewable:
- Calls the change_managed routine of the widgets' parent.
- Calls on each previously unmanaged child that is unrealized.
- Maps each previously unmanaged child that has map_when_managed
Managing children is independent of the ordering of children and independent of creating and deleting children. The layout routine of the
parent should consider children whose managed field is and should ignore all other children. Note that some composite widgets, especially
fixed boxes, call from their insert_child procedure.
If the parent widget is realized, its change_managed procedure is called to notify it that its set of managed children has changed. The
parent can reposition and resize any of its children. It moves each child as needed by calling which first updates the x and y fields and
then calls if the widget is realized.
The function constructs a of length one and calls
The function performs the following:
o Issues an error if the children do not all have the same parent or if the parent is not a subclass of
o Returns immediately if the common parent is being destroyed; otherwise, for each unique child on the list, performs the following:
- Ignores the child if it already is unmanaged or is being destroyed and marks it if not.
- If the child is realized, it makes it nonvisible by unmapping it.
o Calls the change_managed routine of the widgets' parent after all children have been marked if the parent is realized.
does not destroy the children widgets. Removing widgets from a parent's managed set is often a temporary banishment, and, some time later,
you may manage the children again.
The function constructs a widget list of length one and calls
See Also
XtMapWidget(3Xt), XtRealizeWidget(3Xt)
X Window System Toolkit: The Complete Programmer's Guide and Specification, Paul J. Asente and Ralph Swick
X Window System: The Complete Reference, Second Edition, Robert W. Scheifler and James Gettys
XtManageChildren(3Xt)