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Re: [libvirt] [PATCH] qemuxml2argvtest: uncoditionally mock NUMA routines



  Ján Tomko wrote:

> On Fri, May 13, 2016 at 08:53:08PM +0300, Roman Bogorodskiy wrote:
> >   Ján Tomko wrote:
> > 
> > > On Thu, May 12, 2016 at 10:47:04AM +0300, Roman Bogorodskiy wrote:
> > > > Currently, qemuxml2argvmock.c only mocks virNumaNodeIsAvailable(), and
> > > > only if libvirt was built with NUMA support. This causes some test
> > > > failures where NUMA is involved.
> > > > 
> > > 
> > > This is misleading, you are probably compiling with clang, which
> > > inlines virNumaGetMaxNode, so the mocked version of it is never called.
> > > 
> > > With no NUMA support, even libvirtd uses the implementation of
> > > virNumaNodeIsAvailable based on virNumaGetMaxNode.
> > > And the mocked virNumaNodesetIsAvailable is functionally identical to
> > > the implementation in virnuma.c.
> > > 
> > > There were two attempts to get around it:
> > > __attribute__((__noinline__))
> > > https://www.redhat.com/archives/libvir-list/2015-March/msg00203.html
> > > and mocking virNumaNodesetIsAvailable by its identical copy:
> > > https://www.redhat.com/archives/libvir-list/2016-March/msg00515.html
> > > (mocking virNumaNodeIsAvailable should not be needed).
> > > 
> > > All they need is a decision.
> > 
> > It's strange, but neither of these two patches fixes the issue for me.
> > That's with 3.8.0. It starts working only when I pull in both
> > virNumaNodeIsAvailable() and virNumaNodesetIsAvailable() into
> > qemuxml2argvmock.c without the #if WITH_NUMACTL conditional.
> > 
> 
> Right, libvirt's virNumaGetMaxNode gets inlined in
> libvirt's virNumaNodeIsAvailable, and the virNumaGetMaxNode
> defined in tests would not get used.
> 
> ACK to the original patch then. Please mention that this is
> caused by different handling of inlining by clang in a comment
> and/or the commit message.

Thanks, I'll re-word the commit message then. Meanwhile, I was playing
around with this over the weekend and it behaves really weird.

I decided not to use debugger to make sure nothing's caused any
additional side effects and added some debug printf's.

Specifically, I've added logging to all the virNumaGetMaxNode()
implementations, and I've also added some logging to virNumaNodeIsAvailable().

I fail to understand the result. Specifically, it produces the following
output:

virNumaGetMaxNode: mocked, maxnodesNum = 7
virNumaGetMaxNode() = -1
virNumaGetMaxNode: mocked, maxnodesNum = 7
virNumaGetMaxNode() = -1
virNumaGetMaxNode: mocked, maxnodesNum = 7
virNumaGetMaxNode() = -1
virNumaGetMaxNode: mocked, maxnodesNum = 7
virNumaGetMaxNode() = -1
virNumaGetMaxNode: mocked, maxnodesNum = 7
virNumaGetMaxNode() = -1
virNumaGetMaxNode: mocked, maxnodesNum = 7
virNumaNodeIsAvailable: max_node = -1

(I've added a look like
    for (int i = 0; i < 5; i++)
            printf("virNumaGetMaxNode() = %d\n", virNumaGetMaxNode());

So... it is calling the mocked version, but uses -1 as a result. When I
change the real implementation to return e.g. 42 instead of -1, I get
42, but I don't see its logging.

It doesn't change when I add ATTRIBUTE_NOINLINE for virNumaGetMaxNode.
I'm wondering I miss something obvious or maybe my system is screwed?

Debug ideas appreciated. Meanwhile, I'll try to better understand how
LD_PRELOAD works as well as objdump's asm format, but that might take a
while...

Roman Bogorodskiy


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