2.6.15-rt17

[Ingo Molnar <mingo@elte.hu>]

i have released the 2.6.15-rt17 tree, which can be downloaded from the 
usual place:

   http://redhat.com/~mingo/realtime-preempt/

lots of changes all across the map. There are several bigger changes:

the biggest change is the new PI code from Esben Nielsen, Thomas 
Gleixner and Steven Rostedt. This big rework simplifies and streamlines 
the PI code, and fixes a couple of bugs and races:

  - only the top priority waiter on a lock is enqueued into the pi_list
    of the task which holds the lock. No more pi list walking in the
    boost case.

  - simpler locking rules

  - fast Atomic acquire for the non contended case and atomic release 
    for non waiter case is fully functional now

  - use task_t references instead of thread_info pointers

  - BKL handling for semaphore style locks changed so that BKL is
    dropped before the scheduler is entered and reaquired in the return
    path. This solves a possible deadlock situation in the BKL reacquire
    path of the scheduler.

another change is the reworking of the SLAB code: it now closely matches 
the upstream SLAB code, and it should now work on NUMA systems too 
(untested though).

the tasklet code was reworked too to be PREEMPT_RT friendly: the new PI 
code unearthed a fundamental livelock scenario with PREEMPT_RT, and the 
fix was to rework the tasklet code to get rid of the 'retrigger 
softirqs' approach.

other changes: various hrtimers fixes, latency tracer enhancements - and 
more. (Robust-futexes are not expected to work in this release.)

please report any new breakages, and re-report any old breakages as 
well.

to build a 2.6.15-rt17 tree, the following patches should be applied:

  http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.15.tar.bz2
  http://redhat.com/~mingo/realtime-preempt/patch-2.6.15-rt17

	Ingo