Re: [PATCH] Priority Lists for the RT mutex

[Esben Nielsen <simlo@phys.au.dk>]

I looked at the PI-code to see what priority the task (old_owner below)
would end up with when it released a lock. From rt.c:

	prio = mutex_getprio(old_owner);
	if (new_owner && !plist_empty(&new_owner->pi_waiters)) {
		w = plist_entry(&new_owner->pi_waiters, struct
rt_mutex_waiter, pi_list);
		prio = w->task->prio;
	}
	if (prio != old_owner->prio)
		pi_setprio(lock, old_owner, prio);

What has new_owner to do with it? Shouldn't it be old_owner in these
lines? I.e. the prio we want to set old_owner to should be the prio of the
head of the old_owner->pi_waiters, not the new_owner!

Esben


On Mon, 11 Apr 2005, Ingo Molnar wrote:

> 
> * Perez-Gonzalez, Inaky <inaky.perez-gonzalez@intel.com> wrote:
> 
> > Let me re-phrase then: it is a must have only on PI, to make sure you 
> > don't have a loop when doing it. Maybe is a consequence of the 
> > algorithm I chose. -However- it should be possible to disable it in 
> > cases where you are reasonably sure it won't happen (such as kernel 
> > code). In any case, AFAIR, I still did not implement it.
> 
> are there cases where userspace wants to disable deadlock-detection for 
> its own locks?
> 
> the deadlock detector in PREEMPT_RT is pretty much specialized for 
> debugging (it does all sorts of weird locking tricks to get the first 
> deadlock out, and to really report it on the console), but it ought to 
> be possible to make it usable for userspace-controlled locks as well.
> 
> 	Ingo
> 

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