Matt Helsley wrote:
This allows per-task watchers to implement inheritance of the same function
and/or data in response to the initialization of new tasks. A watcher might
implement inheritance using the following notifier_call snippet:
int my_notify_func(struct notifier_block *nb, unsigned long val, void *t)
{
struct task_struct *tsk = t;
struct notifier_block *child_nb;
switch(get_watch_event(val)){
case WATCH_TASK_INIT: /* use container_of() to associate extra data */
child_nb = kzalloc(sizeof(struct notifier_block), GFP_KERNEL);
if (!child_nb)
return NOTIFY_DONE;
child_nb->notifier_call = my_notify_func;
register_per_task_watcher(tsk, child_nb);
return NOTIFY_OK;
case WATCH_TASK_FREE:
unregister_per_task_watcher(tsk, nb);
kfree(nb);
return NOTIFY_OK;
Compile tested only. Peter, is this useful to you?
I think that it's what I want (i.e. the implementation is what I would
have done) but I'm confused by you reference to inheritance. My concern
is to NOT inherit the data (via the notifier_block) but to have separate
data for each task which is why I was concerned about not finding where
"notify" was being initialized on boot.
What I'm doing is using an ordinary watcher to catch new tasks being
created via WATCH_TASK_INIT and attaching a per task watcher to them at
that time. As per your suggestion the notifier_block for the per task
watcher is contained in a struct which contains the data that I need to
maintain for each task. So two layers of watchers :-)
It will be a good test of your mechanism if I can get it to work.
It'll probably take me another couple of days to complete this code as
I'm having to figure out how it all hangs together as I go. I'll let
you know when I've finished.
Peter
--
Peter Williams [email protected]
"Learning, n. The kind of ignorance distinguishing the studious."
-- Ambrose Bierce
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