Re: [patch] voluntary-preempt-2.6.8.1-P2

[Thomas Charbonnel]

Ingo Molnar wrote :
> here's -P2:
> 
>  http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.8.1-P2
> 
> Changes since -P1:
> 
>  - trace interrupted kernel code (via hardirqs, NMIs and pagefaults)
> 
>  - yet another shot at trying to fix the IO-APIC/USB issues.
> 
>  - mcount speedups - tracing should be faster
> 
> 	Ingo
> -

The next problem I have relates to irq sharing. 
On my laptop I can't avoid it :
 10:    1070631          XT-PIC  yenta, yenta, uhci_hcd, Intel
82801CA-ICH3, hdsp, eth0
If I set the sound card's interrupt to be non threaded, then I get a
rather long non preemptible section :
http://www.undata.org/~thomas/irq_sharing.trace

As a side note, and this has already been reported here several times,
the SA_INTERRUPT flag set notably by the sound card drivers handlers is
not honored on current kernels if the device is not the first one to be
registered. A simple fix would be to add SA_INTERRUPT handlers at the
beginning instead of the end of the irq queue in setup_irq.

Similarly, when using SA_SAMPLE_RANDOM, all devices on the given irq
contribute to the entropy, even those that have a predictable interrupt
rate (e.g. sound cards), and/or for which the number of interrupts could
outweight the number of interrupts of the original SA_SAMPLE_RANDOM
driver. 

Thomas


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