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RE: [PATCH 2.5.64] Real-time futexes (priority inheritance/protec tion/robust support) take 4



"Perez-Gonzalez, Inaky" schrieb am 25.03.03 00:54:05:
[...]
> I reached the conclusion that you can only hold more than 
> one pp mutexes only if they have the same prio ceiling, 

Uhmm, "only if they have the same prio ceiling"...

Given: three threads A > B > C [priority wise] and two PP 
locks L1 and L2. The locks are used as follows:

  thread A: L1 
  thread B: L2 
  thread C: L2, L1 [nested].

The assigned ceilings are:

  L1: prty(A)
  L2: prty(B)

To me, this looks just fine. Note that if thread C would 
have "L1, L2" locking order, then according to my reading 
of the standard, the L2-ceiling would have to be raised to 
prty(A) (otherwise, implementation would fail with EINVAL 
on an attempt to lock L2). Or am I just missing and/or 
misunderstanding something?


> and also that the priority boosts you can get can only 
> be up to the priority ceiling.

I'd rather "don't care" and "allow" it to fail with EINVAL  
on an attempt to lock a PP mutex if thread's {"effective"} 
priority is higher than the mutex's ceiling. Oder?

regards,
alexander.

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