Re: PI patch against 2.6.16-rt9

Thomas Gleixner
2006-03-28T21:35:47Z

On Tue, 2006-03-28 at 22:17 +0100, Esben Nielsen wrote:
> I think we talk about the situation

No, we talk about existing lock chains L(0) --> L(n).

> B locks 1 C locks 2 D locks 3
> B locks 2, boosts C and block
> A locks 2
> A is boost B
> A drop it's spinlocks and is preempted
> C unlocks 2 and auto unboosts
> B is running
> B locks 3, boosts C and blocks
> A gets a CPU again
> A boosts B
> A boosts D
>
> Is there anything wrong with that?
> And in the case where A==D there indeed is a deadlock which will be
> detected.

If you get to L(x) the underlying dependencies might have changed
already as well as the dependencies x ... n. We might get false
positives in the deadlock detection that way, as a deadlock is an
"atomic" state.

tglx