Messages in this thread | | | Subject | Re: [RT] bad BUG_ON in rtmutex.c | From | Daniel Walker <> | Date | Tue, 18 Apr 2006 07:51:53 -0700 |
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On Tue, 2006-04-18 at 10:32 -0400, Steven Rostedt wrote:
> > Actually, where that BUG_ON was is the exiting of the chain walk. So it > does stop. It's the higher priority task that needs to be continuing > the chain walk for that problem to occur. So really, it already does > what you suggest :)
I bet you could test for that condition in some other spots too . Like when it adds to the pi_waiters , you could test if the priorities are out of sync ..
> > > > > To keep latencies down, we are letting the PI chain walk be preempted, > > > by releasing locks. It's understood that the chain can then change > > > while walking (big debate about this between Ingo, tglx and Esben). But > > > at the end, we decided on it being better to have latencies down, and > > > just make adjustments when they arise. This also keeps the latencies > > > bounded, since the old way was harder to know the worst case (PI chain > > > creep). > > > > I can imagine. Seems like PI is always a point of controversy . > > But, as PI matures, it seems to be more and more acceptable.
I read an article on priority ceiling as another method of doing this. Priority ceiling doesn't seem better, but at the same time I can't imagine how you'd implement it in Linux, or not in a straight forward way .
> Also, I always test on SMP (then I test on UP) and the chain walkers > were on two CPUs.
Yeah, best policy, I've learned ..
Daniel
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