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

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Eric W. Biederman wrote:
Auke Kok <[email protected]> writes:

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?

Does this patch fix it for you?  It looks like i386 vector allocate
did not have logic to look through the set of vectors more than once.

The code in this patch is a simplified version of what we have
on x86_64.

I highly doubt it - I've seen the problem even on this weeks git on x86_64. Moreover, I'm at home for the weekend and testing resources are limited :). I'll see what I can do

Auke
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