Re: [Xen-devel] [XEN PATCH for-4.13] xen: Fix race to build arch/x86/efi/relocs-dummy.o

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Tue, Nov 19, 2019 at 05:32:53PM +0100, Jan Beulich wrote:
> On 19.11.2019 17:27, Jan Beulich wrote:
> > On 14.11.2019 19:05, Anthony PERARD wrote:
> >> With $(TARGET).efi depending on efi/relocs-dummy.o, arch/x86/Makefile
> >> will attempt to build that object. This result in the dependency file
> >> been generated with relocs-dummy.o depending on efi/relocs-dummy.o.
> >>
> >> Then, when arch/x86/efi/Makefile tries to build relocs-dummy.o, well
> >> efi/relocs-dummy.S doesn't exist.
> >>
> >> Have only one makefile responsible for building relocs-dummy.o.
> > 
> > On a system with too old a tool chain for the EFI build to get
> > enabled I now get about a dozen instances per build of
> > 
> > nm: 'efi/relocs-dummy.o': No such file
> > 
> > I don't suppose you did try out your change in such an oldish
> > environment? I assume the problem are these two lines:
> > 
> > $(TARGET).efi: VIRT_BASE = 0x$(shell $(NM) efi/relocs-dummy.o | sed -n 's, 
> > A VIRT_START$$,,p')
> > $(TARGET).efi: ALT_BASE = 0x$(shell $(NM) efi/relocs-dummy.o | sed -n 's, A 
> > ALT_START$$,,p')
> > 
> > I'm not sure it is well defined when make would evaluate such
> > target specific variable assignments (i.e. I'm not sure this
> > doesn't point out an issue even on EFI capable tool chains).
> > Then again these not using := should cause them to get
> > evaluated only upon use, i.e. never.
> 
> Ah, this was wrong - the $(guard) prefix causes them to get
> evaluated even when xen.efi cannot be built. So I guess this is
> just a cosmetic issue then, which would however still be nice
> to see addressed.

That $(guard) thing is weird, and can probably be replace now.

I'll try to remove that thing, and also avoid having $(TARGET).efi
depending on efi/relocs-dummy.o when it isn't going to be built (when
XEN_BUILD_EFI=n).

-- 
Anthony PERARD

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