Re: Possible regression: MSI vector leakage since 2.6.18-rc5ish (Unableto repeatedly allocate/free MSI interrupt)

[Auke Kok]

Auke Kok wrote:
> Hi,
>
> I've established a regression in the MSI vector/irq allocation routine for both 
> i386 and x86_64. Our test labs repeatedly modprobe/rmmod the e1000 driver for 
> serveral minutes which allocates msi vectors and frees them. These tests have 
> been running fine until 2.6.19.
>
> git-bisecting I've established that in between commit 
> 04b9267b15206fc902a18de1f78de6c82ca47716 "Eric W. Biederman -- genirq: x86_64 
> irq: Remove the msi assumption that irq == vector" and commit 
> f29bd1ba68c8c6a0f50bd678bbd5a26674018f7c "Ingo Molnar -- genirq: convert the 
> x86_64 architecture to irq-chips" the behaviour broke.
>
> The revisions in between seem to be dependent and give all sorts of other 
> issues, so it's rather hard for me to bisect that and give trustworthy results.
>
> the e1000 driver hits the 256-mark cycle (I think - it consistently refuses to 
> do 500 msi irq/vector allocations which is my test case) and throws:
>
> e1000: eth4: e1000_request_irq: Unable to allocate MSI interrupt Error: -16
>
> which is caused by a `if ((err = pci_enable_msi(adapter->pdev))) {` call from 
> the e1000 driver. It's rather easy to hit this mark with the new 4-port e1000 
> adapters :).
>
> as for the e1000 code, I can say that even our oldest msi-enabled e1000 driver 
> works fine with 2.6.18 and under. All kernels from 2.6.19 fail consistently.
>
> I mostly suspect commit 7bd007e480672c99d8656c7b7b12ef0549432c37 at the moment. 
> Perhaps Eric Biederman can help?

PS PS

The exact same problem exists when doing "for n in `seq 1 300` ; do modprobe 
snd_hda_intel enable_msi ; rmmod snd_hda_intel ; done".

I'm sure it will show up for other msi enabled devices.
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