RE: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-25

RE: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-25

[kus Kusche Klaus]

> i have released the -V0.7.41-25 Real-Time Preemption patch, 
> which can be 
> downloaded from the usual place:

1. Does not compile without RT_DEADLOCK_DETECT:
kernel/rt.c: In function `change_owner':
kernel/rt.c:556: error: structure has no member named `debug'
kernel/rt.c: In function `pi_setprio':
kernel/rt.c:576: error: structure has no member named `debug'
kernel/rt.c: In function `task_blocks_on_lock':
kernel/rt.c:677: error: structure has no member named `debug'
kernel/rt.c:687: error: structure has no member named `debug'
kernel/rt.c: In function `__up_mutex':
kernel/rt.c:1223: error: structure has no member named `debug'

2. My problem (see my LKML mails yesterday) is not yet solved:
The latency tracer shows latencies of at most 40 microseconds,
but my test program at rtprio 99 sometimes did not get any CPU 
for milliseconds...

-- 
Klaus Kusche
Entwicklung Software - Steuerung
Software Development - Control

KEBA AG
A-4041 Linz
Gewerbepark Urfahr
Tel +43 / 732 / 7090-3120
Fax +43 / 732 / 7090-8919
E-Mail: kus@keba.com
www.keba.com

Re: [patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-25

[Ingo Molnar]

* kus Kusche Klaus <kus@keba.com> wrote:

> > i have released the -V0.7.41-25 Real-Time Preemption patch, 
> > which can be 
> > downloaded from the usual place:
> 
> 1. Does not compile without RT_DEADLOCK_DETECT:
> kernel/rt.c: In function `change_owner':
> kernel/rt.c:556: error: structure has no member named `debug'

ok - i fixed this in -42-01.

> 2. My problem (see my LKML mails yesterday) is not yet solved: The 
> latency tracer shows latencies of at most 40 microseconds, but my test 
> program at rtprio 99 sometimes did not get any CPU for milliseconds...

(please Cc: me on PREEMPT_RT related mails - i might not notice lkml 
mails.) I'll reply to your lkml mail in a separate thread.

	Ingo

[patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-10

[Ingo Molnar]

i have released the -V0.7.41-10 Real-Time Preemption patch, which can be 
downloaded from the usual place:

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

this release fixes two bugs:

 - one affecting SMP systems & RCU (the missing smp_mb()s)

 - the other one in net/xfrm/xfrm_policy.c, affecting systems where 
   network interfaces (or pseudo-interfaces) are frequently 
   created/destroyed

i've also added a new debugging feature which is activated if 
RT_DEADLOCK_DETECT is enabled: the checking of active locks in freed 
memory.

This catches a dangerous category of bugs which the upstream kernel can 
silently ignore (because there locks are quite 'passive'), while the -RT 
kernel will often go down in flames sometime later (it has lists within 
the lock, etc.). This mechanism found the xfrm_policy.c bug:

 BUG: events/0/4, active lock [e94a8cdc(e94a8cd0-e94a90dc)] freed!
  [<c0103e31>] dump_stack+0x1e/0x20 (20)
  [<c0136fa2>] check_no_locks_freed+0x158/0x210 (60)
  [<c01477e9>] kfree+0x59/0x15a (48)
  [<c03638db>] xfrm_policy_gc_task+0x6f/0x7e (28)
  [<c012f3c7>] worker_thread+0x1c1/0x26c (132)
  [<c01333e9>] kthread+0x95/0xbd (48)
  [<c01012c9>] kernel_thread_helper+0x5/0xb (1039269908)

so i'd expect more such bugs to be found. If you had stability problems 
under PREEMPT_RT (hangs, crashes), please enable RT_DEADLOCK_DETECT and 
try to reproduce the problem and send me the resulting log messages.

to create a -V0.7.41-10 tree from scratch, the patching order is:

  http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.11.tar.bz2
  http://kernel.org/pub/linux/kernel/v2.6/testing/patch-2.6.12-rc1.bz2
  http://redhat.com/~mingo/realtime-preempt/realtime-preempt-2.6.12-rc1-V0.7.41-10

	Ingo

[patch] Real-Time Preemption, -RT-2.6.12-rc1-V0.7.41-25

[Ingo Molnar]

i have released the -V0.7.41-25 Real-Time Preemption patch, which can be 
downloaded from the usual place:

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

this release tries to stabilize things some more. In particular i've 
changed 'nocheck' semaphores to not be included in any PI or debugging 
logic. This makes them pretty much stateless and compatible. XFS seems 
to be working much better with this approach, and maybe some of the 
other problematic subsystems (USB/firewire) will improve too.

there's also a latency tracer fix which should cure some of the 
'truncated traces' problems.

i've also included Trond Myklebust's NFS client patch which should 
reduce latencies in that area (on PREEMPT_DESKTOP/VOLUNTARY kernels - 
under PREEMPT_RT the whole NFS code was fully preemptable already).  
It's experimental so be careful if you are using NFS.

to create a -V0.7.41-25 tree from scratch, the patching order is:

  http://kernel.org/pub/linux/kernel/v2.6/linux-2.6.11.tar.bz2
  http://kernel.org/pub/linux/kernel/v2.6/testing/patch-2.6.12-rc1.bz2
  http://redhat.com/~mingo/realtime-preempt/realtime-preempt-2.6.12-rc1-V0.7.41-25

	Ingo