Re: 2.6.16-rc6-rt1

[John Richard Moser <nigelenki@comcast.net>]

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So Ingo, when are we going to see these in the mainline kernel yet?  I
am particularly interested in priority inheriting semaphores; it seems
like brain damage to have something spin_lock() and block a higher
priority process while other mid-priority processes (i.e. higher than
the blocker but lower than the blocked) are given execution priority.
As I understand, the PI code fixes this by inheriting the priority of
the highest blocked process on a lock into whatever process is holding
the lock, which sounds like exactly what should be happening.

Ingo Molnar wrote:
> i have released the 2.6.16-rc6-rt1 tree, which can be downloaded from 
> the usual place:
> 
>    http://redhat.com/~mingo/realtime-preempt/
> 
> again, lots of changes all over the map:
> 
> - firstly, the -rt tree has been rebased to 2.6.16-rc6, which was a more
>   complex operation than usual, due to the many changes in 2.6.16 (in 
>   particular the mutex code).
> 
> - the PI code got reworked again, this time by Thomas Gleixner. The
>   priority boosting chain is now instantaneous again (and not 
>   wakeup/scheduling based) - but the previous list-walking hell has been 
>   avoided via the clever use of plists. Plus many other changes and
>   lots of cleanups to the rt-mutex proper.
> 
> - the rt-SLAB code got reworked too - hopefully for the better.
> 

I have not heard anything about your SLAB code before.  Think you can
give me a basic idea of what it's supposed to do?

> - there's also a completely new PI-futex approach included, ontop of the
>   robust-list futex feature. All combinations of PI and robustness are
>   supported: default non-robust non-PI futexes, robust+PI, !robust+PI,
>   PI+!robust futexes.
> 

I don't know what non-robust futex means.  Also don't you mean
!robust+!PI (00), robust+PI (11), !robust+PI (01), robust+!PI (10)?  The
last two on your list look to be the same thing :)

> - new latency tracer feature: print every function call done by the
>   kernel to the console - useful to debug early bootup hangs or other
>   nasty bugs.
> 
> - plus zillions of bugfixes (and no doubt new regressions).
> 

Regressions are going to be the answer to my "when is some of this going
into mainline" question, aren't they :P

> to build a 2.6.16-rc6-rt1 tree, the following patches should be applied:
> 
>   http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.15.tar.bz2
>   http://kernel.org/pub/linux/kernel/v2.6/testing/patch-2.6.16-rc6.bz2
>   http://redhat.com/~mingo/realtime-preempt/patch-2.6.16-rc6-rt1
> 
> 	Ingo
> -
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