libthr patch

[Mike Makonnen]

On Fri, Feb 20, 2004 at 12:47:33AM +1100, Tim Robbins wrote:
> On Thu, Feb 19, 2004 at 09:28:50AM +0300, Mike Makonnen wrote:
> 
> Make sure you fix thr_wake() to check that uap->id is valid before you
> commit this patch. Something like this would be safer but slower:

Hmm, you're right. I should've thought of that. Thanks for catching it.

> 
> 	struct thread *td1;
> 
> 	PROC_LOCK(td->td_proc);
> 	FOREACH_THREAD_IN_PROC(td->td_proc, td1)
> 		if (td1 == (struct thread *)uap->id)
> 			break;
> 	if (td1 == NULL) {
> 		PROC_UNLOCK(td->td_proc);
> 		return (ESRCH);
> 	}
> 	td1->td_lthrflags |= LTF_THRWAKEUP;
> 	wakeup_one(td1);
> 	PROC_UNLOCK(td->td_proc);
> 	return (0);
> 
> (I'm not sure that it's safe to call wakeup_one() on a thread pointer
> that isn't curthread without holding the proc lock, so I changed that too.)

Sorry, I don't follow. How can a thread call wakeup_one() on itself (if it's
supposed to be asleep)?

A cursory look through the call path doesn't show anything that needs a
proc lock. There is access to p->p_state but either sched_lock or proc lock
is sufficient for that (and the accessing function does hold sched_lock).

Cheers.
-- 
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