build: remove use of MAKELEVEL optimization in submodule handling

The Makefile attempts to optimize the handling of submodules by using MAKELEVEL
to only check the submodule status when running from the top level make
invokation. This causes problems for people who are using a makefile of their
own to in turn invoke QEMU's makefile, as MAKELEVEL is already set to 1 (or
more) when QEMU's makefile runs.

This optimization should not really be needed, since the git-submodule.sh
script is already used to detect if a submodule update is required. This by
removing the MAKELEVEL check, we at most add an extra 'git-submodule.sh status'
call to each make level, the overhead of which is lost in noise of building
QEMU.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---

NB this is on top of https://lists.gnu.org/archive/html/qemu-devel/2017-11/msg00449.html

 Makefile | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

On Mon,  6 Nov 2017 11:41:34 +0000
"Daniel P. Berrange" <berrange@redhat.com> wrote:

> The Makefile attempts to optimize the handling of submodules by using MAKELEVEL
> to only check the submodule status when running from the top level make
> invokation. This causes problems for people who are using a makefile of their
> own to in turn invoke QEMU's makefile, as MAKELEVEL is already set to 1 (or
> more) when QEMU's makefile runs.
> 
> This optimization should not really be needed, since the git-submodule.sh
> script is already used to detect if a submodule update is required. This by
> removing the MAKELEVEL check, we at most add an extra 'git-submodule.sh status'
> call to each make level, the overhead of which is lost in noise of building
> QEMU.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
> 

Heh, I had come up with a similar patch based on master and nearly the
same commit message. :)

Reviewed-by: Greg Kurz <groug@kaod.org>

> NB this is on top of https://lists.gnu.org/archive/html/qemu-devel/2017-11/msg00449.html
> 

I could check that this patch applied on top of the series mentioned above
fixes the issue for me.

Tested-by: Greg Kurz <groug@kaod.org>

>  Makefile | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index a92d7b8e14..0496c5057a 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -18,12 +18,11 @@ git-submodule-update:
>  
>  .PHONY: git-submodule-update
>  
> -ifeq (0,$(MAKELEVEL))
> -  git_module_status := $(shell \
> -    cd '$(SRC_PATH)' && \
> -    GIT="$(GIT)" ./scripts/git-submodule.sh status $(GIT_SUBMODULES); \
> -    echo $$?; \
> -  )
> +git_module_status := $(shell \
> +  cd '$(SRC_PATH)' && \
> +  GIT="$(GIT)" ./scripts/git-submodule.sh status $(GIT_SUBMODULES); \
> +  echo $$?; \
> +)
>  
>  ifeq (1,$(git_module_status))
>  ifeq (no,$(GIT_UPDATE))
> @@ -42,7 +41,6 @@ git-submodule-update:
>            "GIT","$(GIT_SUBMODULES)")
>  endif
>  endif
> -endif
>  
>  .git-submodule-status: git-submodule-update config-host.mak
>

On 11/06/2017 05:41 AM, Daniel P. Berrange wrote:
> The Makefile attempts to optimize the handling of submodules by using MAKELEVEL
> to only check the submodule status when running from the top level make
> invokation. This causes problems for people who are using a makefile of their

s/invokation/invocation/

> own to in turn invoke QEMU's makefile, as MAKELEVEL is already set to 1 (or
> more) when QEMU's makefile runs.
> 
> This optimization should not really be needed, since the git-submodule.sh
> script is already used to detect if a submodule update is required. This by

s/This/Thus/

> removing the MAKELEVEL check, we at most add an extra 'git-submodule.sh status'
> call to each make level, the overhead of which is lost in noise of building
> QEMU.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
> 
> NB this is on top of https://lists.gnu.org/archive/html/qemu-devel/2017-11/msg00449.html

Or in wording understood by patchew:

Based-on:
https://lists.gnu.org/archive/html/qemu-devel/2017-11/msg00449.html

Reviewed-by: Eric Blake <eblake@redhat.com>