[Qemu-devel] [PATCH] Makefile: fix up parallel building under MSYS+MinGW

[Qemu-devel] [PATCH] Makefile: fix up parallel building under MSYS+MinGW

[Vasily Efimov]

This patch enables parallel building of QEMU in MSYS+MinGW environment.
Currently an attempt to build QEMU in parallel fails on generation of
version.lo (and version.o too).

The cause of the failure is that when listing prerequisites "Makefile"
references "config-host.h" by absolute path in some rules and by relative
path in others. Make cannot figure out that these references points to the
same file which leads to the race: the generation of "version.*" which
requires "$(BUILD_DIR)/config-host.h" is launched in parallel with the
generation of "config-host.h" needed by other "Makefile" targets.

This patch removes "$(BUILD_DIR)/" prefix from corresponding prerequisite
of "version.*". There is no other prerequisites "$(BUILD_DIR)/config-host.h"
found.

Also note that not every version of MSYS is able to build QEMU in parallel,
see: "http://sourceforge.net/p/mingw/bugs/1950/". The suggested version is
1.0.17.

Signed-off-by: Vasily Efimov <real@ispras.ru>
---
 Makefile | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 6817c6f..b0d8c07 100644
--- a/Makefile
+++ b/Makefile
@@ -197,9 +197,9 @@ ALL_SUBDIRS=$(TARGET_DIRS) $(patsubst %,pc-bios/%, $(ROMS))
 
 recurse-all: $(SUBDIR_RULES) $(ROMSUBDIR_RULES)
 
-$(BUILD_DIR)/version.o: $(SRC_PATH)/version.rc $(BUILD_DIR)/config-host.h | $(BUILD_DIR)/version.lo
+$(BUILD_DIR)/version.o: $(SRC_PATH)/version.rc config-host.h | $(BUILD_DIR)/version.lo
 	$(call quiet-command,$(WINDRES) -I$(BUILD_DIR) -o $@ $<,"  RC    version.o")
-$(BUILD_DIR)/version.lo: $(SRC_PATH)/version.rc $(BUILD_DIR)/config-host.h
+$(BUILD_DIR)/version.lo: $(SRC_PATH)/version.rc config-host.h
 	$(call quiet-command,$(WINDRES) -I$(BUILD_DIR) -o $@ $<,"  RC    version.lo")
 
 Makefile: $(version-obj-y) $(version-lobj-y)
-- 
1.9.5.msysgit.0

Re: [Qemu-devel] [PATCH] Makefile: fix up parallel building under MSYS+MinGW

[Paolo Bonzini]

On 18/02/2015 13:59, Vasily Efimov wrote:
> This patch enables parallel building of QEMU in MSYS+MinGW environment.
> Currently an attempt to build QEMU in parallel fails on generation of
> version.lo (and version.o too).
> 
> The cause of the failure is that when listing prerequisites "Makefile"
> references "config-host.h" by absolute path in some rules and by relative
> path in others. Make cannot figure out that these references points to the
> same file which leads to the race: the generation of "version.*" which
> requires "$(BUILD_DIR)/config-host.h" is launched in parallel with the
> generation of "config-host.h" needed by other "Makefile" targets.
> 
> This patch removes "$(BUILD_DIR)/" prefix from corresponding prerequisite
> of "version.*". There is no other prerequisites "$(BUILD_DIR)/config-host.h"
> found.
> 
> Also note that not every version of MSYS is able to build QEMU in parallel,
> see: "http://sourceforge.net/p/mingw/bugs/1950/". The suggested version is
> 1.0.17.
> 
> Signed-off-by: Vasily Efimov <real@ispras.ru>
> ---
>  Makefile | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/Makefile b/Makefile
> index 6817c6f..b0d8c07 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -197,9 +197,9 @@ ALL_SUBDIRS=$(TARGET_DIRS) $(patsubst %,pc-bios/%, $(ROMS))
>  
>  recurse-all: $(SUBDIR_RULES) $(ROMSUBDIR_RULES)
>  
> -$(BUILD_DIR)/version.o: $(SRC_PATH)/version.rc $(BUILD_DIR)/config-host.h | $(BUILD_DIR)/version.lo
> +$(BUILD_DIR)/version.o: $(SRC_PATH)/version.rc config-host.h | $(BUILD_DIR)/version.lo
>  	$(call quiet-command,$(WINDRES) -I$(BUILD_DIR) -o $@ $<,"  RC    version.o")
> -$(BUILD_DIR)/version.lo: $(SRC_PATH)/version.rc $(BUILD_DIR)/config-host.h
> +$(BUILD_DIR)/version.lo: $(SRC_PATH)/version.rc config-host.h
>  	$(call quiet-command,$(WINDRES) -I$(BUILD_DIR) -o $@ $<,"  RC    version.lo")
>  
>  Makefile: $(version-obj-y) $(version-lobj-y)
> 

Applied, thanks.

Paolo

Re: [Qemu-devel] [PATCH] Makefile: fix up parallel building under MSYS+MinGW

[Peter Maydell]

On 18 February 2015 at 21:59, Vasily Efimov <real@ispras.ru> wrote:
> This patch enables parallel building of QEMU in MSYS+MinGW environment.
> Currently an attempt to build QEMU in parallel fails on generation of
> version.lo (and version.o too).
>
> The cause of the failure is that when listing prerequisites "Makefile"
> references "config-host.h" by absolute path in some rules and by relative
> path in others. Make cannot figure out that these references points to the
> same file which leads to the race: the generation of "version.*" which
> requires "$(BUILD_DIR)/config-host.h" is launched in parallel with the
> generation of "config-host.h" needed by other "Makefile" targets.

Thanks for looking into this -- I'd run into the problem a couple
of times but not been able to track down why it was happening...

-- PMM