[Xenomai-core] [PATCH] Fix host IRQ propagation (was: Troubles with switchtest)

2009-05-13 Thread Jan Kiszka 
Philippe Gerum wrote:
 On Wed, 2009-05-13 at 15:18 +0200, Jan Kiszka wrote:
 Gilles Chanteperdrix wrote:
 Jan Kiszka wrote:
 Hi Gilles,

 I'm currently facing a nasty effect with switchtest over latest git head
 (only tested this so far): running it inside my test VM (ie. with
 frequent excessive latencies) I get a stalled Linux timer IRQ quite
 quickly. System is otherwise still responsive, Xenomai timers are still
 being delivered, other Linux IRQs too. switchtest complained about

 Warning: Linux is compiled to use FPU in kernel-space.

 when it was started. Kernels are 2.6.28.9/ipipe-x86-2.2-07 and
 2.6.29.3/ipipe-x86-2.3-01 (LTTng patched in, but unused), both show the
 same effect.

 Seen this before?
 The warning about Linux being compiled to use FPU in kernel-space means
 that you enabled soft RAID or compiled for K7, Geode, or any other
 RAID is on (ordinary server config).

 configuration using 3DNow for such simple operations as memcpy. It is
 harmless, it simply means that switchtest can not use fpu in kernel-space.

 The bug you have is probably the same as the one described here, which I
 am able to reproduce on my atom:
 https://mail.gna.org/public/xenomai-help/2009-04/msg00200.html

 Unfortunately, I for one am working on ARM issues and am not available
 to debug x86 issues. I think Philippe is busy too...
 OK, looks like I got the same flu here.

 Philippe, did you find out any more details in the meantime? Then I'm
 afraid I have to pick this up.
 
 No, I did not resume this task yet. Working from the powerpc side of the
 universe here.

Hoho, don't think this rain here over x86 would have never made it down
to ARM or PPC land! ;)

Martin, could you check if this helps you, too?

Jan

(as usual, ready to be pulled from 'for-upstream')

-

Host IRQs may not only be triggered from non-root domains. But
rthal_propagate_irq's implemenation in I-pipe assumes so, which broke
host tick propagation under certain load scenarios. Besides that,
rthal_schedule_irq_root is the more efficient service for this purpose
anyway.

Signed-off-by: Jan Kiszka jan.kis...@siemens.com
---

 include/asm-generic/hal.h |2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/include/asm-generic/hal.h b/include/asm-generic/hal.h
index b37e476..8137856 100644
--- a/include/asm-generic/hal.h
+++ b/include/asm-generic/hal.h
@@ -437,7 +437,7 @@ int rthal_irq_host_release(unsigned irq,
 
 static inline void rthal_irq_host_pend(unsigned irq)
 {
-   rthal_propagate_irq(irq);
+   rthal_schedule_irq_root(irq);
 }
 
 int rthal_apc_alloc(const char *name,

-- 
Siemens AG, Corporate Technology, CT SE 2
Corporate Competence Center Embedded Linux

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Re: [Xenomai-core] [PATCH] Fix host IRQ propagation (was: Troubles with switchtest)

2009-05-13 Thread Philippe Gerum 
On Wed, 2009-05-13 at 17:28 +0200, Jan Kiszka wrote:
 Philippe Gerum wrote:
  On Wed, 2009-05-13 at 15:18 +0200, Jan Kiszka wrote:
  Gilles Chanteperdrix wrote:
  Jan Kiszka wrote:
  Hi Gilles,
 
  I'm currently facing a nasty effect with switchtest over latest git head
  (only tested this so far): running it inside my test VM (ie. with
  frequent excessive latencies) I get a stalled Linux timer IRQ quite
  quickly. System is otherwise still responsive, Xenomai timers are still
  being delivered, other Linux IRQs too. switchtest complained about
 
  Warning: Linux is compiled to use FPU in kernel-space.
 
  when it was started. Kernels are 2.6.28.9/ipipe-x86-2.2-07 and
  2.6.29.3/ipipe-x86-2.3-01 (LTTng patched in, but unused), both show the
  same effect.
 
  Seen this before?
  The warning about Linux being compiled to use FPU in kernel-space means
  that you enabled soft RAID or compiled for K7, Geode, or any other
  RAID is on (ordinary server config).
 
  configuration using 3DNow for such simple operations as memcpy. It is
  harmless, it simply means that switchtest can not use fpu in kernel-space.
 
  The bug you have is probably the same as the one described here, which I
  am able to reproduce on my atom:
  https://mail.gna.org/public/xenomai-help/2009-04/msg00200.html
 
  Unfortunately, I for one am working on ARM issues and am not available
  to debug x86 issues. I think Philippe is busy too...
  OK, looks like I got the same flu here.
 
  Philippe, did you find out any more details in the meantime? Then I'm
  afraid I have to pick this up.
  
  No, I did not resume this task yet. Working from the powerpc side of the
  universe here.
 
 Hoho, don't think this rain here over x86 would have never made it down
 to ARM or PPC land! ;)
 
 Martin, could you check if this helps you, too?
 
 Jan
 
 (as usual, ready to be pulled from 'for-upstream')
 
 -
 
 Host IRQs may not only be triggered from non-root domains.

Are you sure of this? I can't find any spot where this assumption would
be wrong. host_pend() is basically there to relay RT timer ticks and
device IRQs, and this only happens on behalf of the pipeline head. At
least, this is how rthal_irq_host_pend() should be used in any case. If
you did find a spot where this interface is being called from the lower
stage, then this is the root bug to fix.

  But
 rthal_propagate_irq's implemenation in I-pipe assumes so, which broke
 host tick propagation under certain load scenarios. Besides that,
 rthal_schedule_irq_root is the more efficient service for this purpose
 anyway.

Ack.

 
 Signed-off-by: Jan Kiszka jan.kis...@siemens.com
 ---
 
  include/asm-generic/hal.h |2 +-
  1 files changed, 1 insertions(+), 1 deletions(-)
 
 diff --git a/include/asm-generic/hal.h b/include/asm-generic/hal.h
 index b37e476..8137856 100644
 --- a/include/asm-generic/hal.h
 +++ b/include/asm-generic/hal.h
 @@ -437,7 +437,7 @@ int rthal_irq_host_release(unsigned irq,
  
  static inline void rthal_irq_host_pend(unsigned irq)
  {
 - rthal_propagate_irq(irq);
 + rthal_schedule_irq_root(irq);
  }
  
  int rthal_apc_alloc(const char *name,
 
-- 
Philippe.



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Re: [Xenomai-core] [PATCH] Fix host IRQ propagation (was: Troubles with switchtest)

2009-05-13 Thread Martin Shepherd 

On Wed, 13 May 2009, Jan Kiszka wrote:
...
 Martin, could you check if this helps you, too?

It doesn't appear to help. To check, first I turned on the HPET and PM
timer options, and recompiled the kernel without your patch, to verify
that this reproduced the problem. I then manually applied your patch
to include/asm-generic/xenomai/hal.h in the kernel source tree,
recompiled the kernel, installed etc, and rebooted. However even with
the patch in place, whenever I ran:

  dd if=/dev/zero of=/dev/null count=2000

then initially top showed that dd was getting very little CPU time
(10%), then after 30 seconds or so, the system became completely
unresponsive until the dd ended. This is how it acts without the patch
as well. So it doesn't appear that the patch has made any difference
to this problem.

Note that I applied the patch to Xenomai 2.5-rc1 in linux kernel
2.6.29.1. If the patch somehow relies on head, tell me, and I'll
endeavor to set up a new kernel using that.

Martin

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