Re: [Qemu-block] [Qemu-devel] [PATCH for-2.9] mirror: Fix backwards mirror_yield parameters

[Daniel P. Berrange]

On Wed, Mar 15, 2017 at 06:18:35PM +0800, Stefan Hajnoczi wrote:
> On Fri, Mar 10, 2017 at 02:49:22PM -0600, Eric Blake wrote:
> > And here's where I'm stuck: the makefiles are broken.  Touching
> > scripts/tracetool/format/h.py does NOT cause tracetool to be re-run by a
> > mere 'make'; I've had to resort to 'make -B block/trace.h-timestamp' to
> > get things to rebuild.  And this is in spite of the fact that h.py
> > _should_ be getting listed in $(tracetool-y) by trace/Makefile.objs, and
> > $(tracetool-y) is listed as a dependency of %/trace.h-timestamp in the
> > top-level Makefile.  I would appreciate anyone with advice or an idea on
> > how to patch Makefile to get the dependency working without me having to
> > manually kick it.
> 
> Also CCing Daniel Berrange.  He recently touched the tracing Makefiles
> and may have ideas.

I've been looking at this and I'm damned if I understand what's broken.
All the required dependancies look to be expressed in the Makefile

  %/trace.h: %/trace.h-timestamp
  %/trace.h-timestamp: $(SRC_PATH)/%/trace-events $(tracetool-y)

and $(tracetool-y) expands to the list of source files

  tracetool-y = $(SRC_PATH)/scripts/tracetool.py
  tracetool-y += $(shell find $(SRC_PATH)/scripts/tracetool -name "*.py")


If I do 'touch hw/net/trace-events', then hw/net/trace.h gets rebuilt,
but if do 'touch scripts/tracetool.py' it doesn't get built. So somehow
make seems to be dropping the $(tracetool-y) deps despite being listed
against the %/trace-h-timestamp file, and despite earlier deps on
trace-events being honoured

Regards,
Daniel
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