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Subject: Re: [PATCH 3/7] PCI PM: Fix saving of device state in
 pci_legacy_suspend
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: michael@ellerman.id.au
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Date: Thu, 05 Feb 2009 12:29:23 +1100
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> > Yup, missed that change in the patch. In fact, I even missed the
> > existence of a WARN_ONCE that takes those text arguments... baaaah. I
> > suppose I should try to read more of lkml :-)
> 
> But don't expect to see them on powerpc, they never make it to the
> console.

Allright, that's the problem with our implementation of WARN using a
conditional trap, we don't carry all the variable arguments for the
printf over.

I'm tempted to turn our implementation back to normal C code with an if
and a branch out of line, but Michael seems to say that even with
appropriate use of unlikely() etc... gcc decides to generate the worst
possible code every single time ...

<rant>
such as always inlining the whole printf mumbo jumbo and having the
not-warning case branch over it, not -all- CPUs have good branch
prediction dude, so the icache is going to scream but gcc folks know
better of course....
</rant>

Anyway, I'll see Michael what exactly the situation is here and if we
can fix it a way or another.

Ben.