Re: [patch] Minor PAGG attach/detach semantic change for 2.6.11

On Tue, Sep 27, 2005 at 03:10:20PM -0500, Erik Jacobson wrote:
> I fixed this in the RCU version of pnotify I'm working per the lse-tech 
> community discussion - thanks for the reminder the other day (in a non-list 
> email).
> 
> If the RCU version crashes and burns for some reason and we go back to
> the non-CUu one, I'll need to make the fix there too.  The function now
> looks like this.  I hope this is what you had in mind (untested as of
> this moment).

Erik,

I'm not sure that it does at this moment, not seeing the code for
copy_process() or __pnotify_exit().

__pnotify_exit() would need to call the exit callback for all clients
except for the client failing the fork call.  To do this wouldn't the
following be needed in __pnotify_fork()?

> int
> __pnotify_fork(struct task_struct *to_task, struct task_struct *from_task)
> {
> 	struct pnotify_subscriber *from_subscriber;
> 	int ret;
> 
> 	/* We need to be sure the parent's list we copy from doesn't disappear */
> 	rcu_read_lock();
> 
> 	list_for_each_entry_rcu(from_subscriber, &from_task->pnotify_subscriber_list, entry) {
> 		struct pnotify_subscriber *to_subscriber = NULL;
> 
> 		to_subscriber = pnotify_subscribe(to_task, from_subscriber->events);
> 		if (!to_subscriber) {
> 			ret=-ENOMEM;
> 			__pnotify_exit(to_task);
> 			rcu_read_unlock();
> 			return ret;
> 		}
> 		ret = to_subscriber->events->fork(to_task, to_subscriber,
> 		  from_subscriber->data);
> 	
> 		rcu_read_unlock(); /* no more to do with the parent's data */
> 

Then, to make sure the current client does not have his exit callback
invoked:

		...
		if (ret != 0) {
			pnotify_unsubscribe(to_subscriber);
			if (ret < 0)
				return ret;
	 	}
	}

	return 0;
}

What do you think?

-- 
		Kingsley