[Adeos-main] CONFIG_PREEMPT doesn't work with ADEOS

[Adeos-main] CONFIG_PREEMPT doesn't work with ADEOS

[Bernhard Walle]

Hello,

I have a kernel 2.6.15.6 with
http://download.gna.org/adeos/patches/v2.6/i386/adeos-ipipe-2.6.15-i386-1.2-03.patch
patch. In this configuration, CONFIG_PREEMPT doesn't work any more,
i.e. the kernel is not preempted.

With the kernel without ADEOS patch, it works fine. A test program is
at http://www.bwalle.de/temp/kern-preempt.tar.bz2.

Do you know what's wrong?


Regards,
  Bernhard
-- 
Bei der Eroberung des Weltraums sind zwei Probleme zu lösen: die
Schwerkraft und der Papierkrieg. Mit der Schwerkraft wären wir fertig
geworden. -- Wernher von Braun

Re: [Adeos-main] CONFIG_PREEMPT doesn't work with ADEOS

[Philippe Gerum]

Bernhard Walle wrote:
> Hello,
> 
> I have a kernel 2.6.15.6 with
> http://download.gna.org/adeos/patches/v2.6/i386/adeos-ipipe-2.6.15-i386-1.2-03.patch
> patch. In this configuration, CONFIG_PREEMPT doesn't work any more,
> i.e. the kernel is not preempted.
> 

How do you check this?

> With the kernel without ADEOS patch, it works fine. A test program is
> at http://www.bwalle.de/temp/kern-preempt.tar.bz2.
> 
> Do you know what's wrong?
> 
> 
> Regards,
>   Bernhard


-- 

Philippe.

Re: [Adeos-main] CONFIG_PREEMPT doesn't work with ADEOS

[Philippe Gerum]

Philippe Gerum wrote:
> Bernhard Walle wrote:
> 
>> Hello,
>>
>> I have a kernel 2.6.15.6 with
>> http://download.gna.org/adeos/patches/v2.6/i386/adeos-ipipe-2.6.15-i386-1.2-03.patch 
>>
>> patch. In this configuration, CONFIG_PREEMPT doesn't work any more,
>> i.e. the kernel is not preempted.
>>
> 
> How do you check this?
> 

Forget about this question. I'm going to give a look at your testcase 
when time allows. Thanks.

>> With the kernel without ADEOS patch, it works fine. A test program is
>> at http://www.bwalle.de/temp/kern-preempt.tar.bz2.
>>
>> Do you know what's wrong?
>>
>>
>> Regards,
>>   Bernhard
> 
> 
> 


-- 

Philippe.

Re: [Adeos-main] CONFIG_PREEMPT doesn't work with ADEOS

[Jan Kiszka]

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Philippe Gerum wrote:
> Philippe Gerum wrote:
>> Bernhard Walle wrote:
>>
>>> Hello,
>>>
>>> I have a kernel 2.6.15.6 with
>>> http://download.gna.org/adeos/patches/v2.6/i386/adeos-ipipe-2.6.15-i386-1.2-03.patch
>>>
>>> patch. In this configuration, CONFIG_PREEMPT doesn't work any more,
>>> i.e. the kernel is not preempted.
>>>
>>
>> How do you check this?
>>
> 
> Forget about this question. I'm going to give a look at your testcase
> when time allows. Thanks.
> 

I did, and I can confirm this (2.6.16, original ipipe-1.2-03 applied,
ipipe on vs. off). Maybe something related to the TASK_ATOMICSWITCH changes?

>>> With the kernel without ADEOS patch, it works fine. A test program is
>>> at http://www.bwalle.de/temp/kern-preempt.tar.bz2.
>>>
>>> Do you know what's wrong?
>>>
>>>
>>> Regards,
>>>   Bernhard
>>
>>
>>

Jan


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Re: [Adeos-main] CONFIG_PREEMPT doesn't work with ADEOS

[Philippe Gerum]

Jan Kiszka wrote:
> Philippe Gerum wrote:
> 
>>Philippe Gerum wrote:
>>
>>>Bernhard Walle wrote:
>>>
>>>
>>>>Hello,
>>>>
>>>>I have a kernel 2.6.15.6 with
>>>>http://download.gna.org/adeos/patches/v2.6/i386/adeos-ipipe-2.6.15-i386-1.2-03.patch
>>>>
>>>>patch. In this configuration, CONFIG_PREEMPT doesn't work any more,
>>>>i.e. the kernel is not preempted.
>>>>
>>>
>>>How do you check this?
>>>
>>
>>Forget about this question. I'm going to give a look at your testcase
>>when time allows. Thanks.
>>
> 
> 
> I did, and I can confirm this (2.6.16, original ipipe-1.2-03 applied,
> ipipe on vs. off). Maybe something related to the TASK_ATOMICSWITCH changes?
> 

Don't know yet, I'm rebuilding an instrumented kernel, but considering 
that we don't even have local echo of keystrokes, I'd rather think of 
IRQs lagging in the pipeline log. More news later.

> 
>>>>With the kernel without ADEOS patch, it works fine. A test program is
>>>>at http://www.bwalle.de/temp/kern-preempt.tar.bz2.
>>>>
>>>>Do you know what's wrong?
>>>>
>>>>
>>>>Regards,
>>>>  Bernhard
>>>
>>>
>>>
> 
> Jan
> 
> 
> 
> ------------------------------------------------------------------------
> 
> _______________________________________________
> Adeos-main mailing list
> Adeos-main@domain.hid
> https://mail.gna.org/listinfo/adeos-main


-- 

Philippe.

Re: [Adeos-main] CONFIG_PREEMPT doesn't work with ADEOS

[Philippe Gerum]

Philippe Gerum wrote:
> Jan Kiszka wrote:
> 
>> Philippe Gerum wrote:
>>
>>> Philippe Gerum wrote:
>>>
>>>> Bernhard Walle wrote:
>>>>
>>>>
>>>>> Hello,
>>>>>
>>>>> I have a kernel 2.6.15.6 with
>>>>> http://download.gna.org/adeos/patches/v2.6/i386/adeos-ipipe-2.6.15-i386-1.2-03.patch 
>>>>>
>>>>>
>>>>> patch. In this configuration, CONFIG_PREEMPT doesn't work any more,
>>>>> i.e. the kernel is not preempted.
>>>>>
>>>>
>>>> How do you check this?
>>>>
>>>
>>> Forget about this question. I'm going to give a look at your testcase
>>> when time allows. Thanks.
>>>
>>
>>
>> I did, and I can confirm this (2.6.16, original ipipe-1.2-03 applied,
>> ipipe on vs. off). Maybe something related to the TASK_ATOMICSWITCH 
>> changes?
>>
> 
> Don't know yet, I'm rebuilding an instrumented kernel, but considering 
> that we don't even have local echo of keystrokes, I'd rather think of 
> IRQs lagging in the pipeline log. More news later.
> 

Er, the softlockup detector triggers while the module holds the CPU, so 
the timer top-half must be running properly. Something is possibly fishy 
in the IRQ return path for x86 from resume_kernel and beyond.

>>
>>>>> With the kernel without ADEOS patch, it works fine. A test program is
>>>>> at http://www.bwalle.de/temp/kern-preempt.tar.bz2.
>>>>>
>>>>> Do you know what's wrong?
>>>>>
>>>>>
>>>>> Regards,
>>>>>  Bernhard
>>>>
>>>>
>>>>
>>>>
>>
>> Jan
>>
>>
>>
>> ------------------------------------------------------------------------
>>
>> _______________________________________________
>> Adeos-main mailing list
>> Adeos-main@domain.hid
>> https://mail.gna.org/listinfo/adeos-main
> 
> 
> 


-- 

Philippe.

Re: [Adeos-main] CONFIG_PREEMPT doesn't work with ADEOS

[Philippe Gerum]

Bernhard Walle wrote:
> Hello,
> 
> I have a kernel 2.6.15.6 with
> http://download.gna.org/adeos/patches/v2.6/i386/adeos-ipipe-2.6.15-i386-1.2-03.patch
> patch. In this configuration, CONFIG_PREEMPT doesn't work any more,
> i.e. the kernel is not preempted.
> 
> With the kernel without ADEOS patch, it works fine. A test program is
> at http://www.bwalle.de/temp/kern-preempt.tar.bz2.
> 
> Do you know what's wrong?
> 
> 

Ok, bug confirmed and spotted. It's an x86 specific issue that impacts 
Adeos back in the pre-Ipipe times. An updated patch will follow once I 
made sure that the fix does not cause any regression, especially on SMP 
systems. Thanks for reporting this way, the quality of your testcase 
made a real difference to locate the issue rapidly.

-- 

Philippe.

Re: [Adeos-main] CONFIG_PREEMPT doesn't work with ADEOS

[Philippe Gerum]

Bernhard Walle wrote:
> Hello,
> 
> I have a kernel 2.6.15.6 with
> http://download.gna.org/adeos/patches/v2.6/i386/adeos-ipipe-2.6.15-i386-1.2-03.patch
> patch. In this configuration, CONFIG_PREEMPT doesn't work any more,
> i.e. the kernel is not preempted.
> 
> With the kernel without ADEOS patch, it works fine. A test program is
> at http://www.bwalle.de/temp/kern-preempt.tar.bz2.
> 
> Do you know what's wrong?
> 

This should improve things quite a bit:

--- arch/i386/kernel/entry.S~	2006-03-21 14:34:51.000000000 +0100
+++ arch/i386/kernel/entry.S	2006-04-18 15:38:50.000000000 +0200
@@ -231,7 +231,7 @@

  #ifdef CONFIG_PREEMPT
  ENTRY(resume_kernel)
-	CLI
+	cli
  	cmpl $0,TI_preempt_count(%ebp)	# non-zero preempt_count ?
  	jnz restore_nocheck
  need_resched:

-- 

Philippe.