Re: [TRIVIAL][PATCH] fix parallel builds for aic7xxx]

[Sam Ravnborg <sam@ravnborg.org>]

Hi Justin, John.

I agree with Justin that the patch for aic7xxx/Makefile looks a bit suspisious.
I have modifed it to use a phony target as serialisation point.
In this way it is more obvious what is actually happening.
The patch for aicasm/Makefile looked OK - included here as well to make the
patch complete.

I have tested this patch on UP only, with make -j4.
Before it broke in aicasm, now it succeeds.

Justin, does this look OK for you?


On Fri, Sep 05, 2003 at 09:36:25AM -0700, John Cherry wrote:
> Short story: 
> 
> The makefile changes separate targets with identical dependencies.  In
> the current Makefiles, things like "running the assembler" and "changing
> file names" happen multiple times in parallel when building with
> anything other than -j1.  Consider the following example Makefile:
> 
> targ: a b
> a b: x
>         touch a b
> x:
>         touch x
> clean:
>         rm a b x
> 
> Running the build with "make targ" yields:
> touch x
> touch a b
> 
> Running the build with "make -j2 targ" yields:
> touch x
> touch a b
> touch a b
> 
> Notice that the "touch a b" output is not only executed twice, but on an
> SMP machine, it could be run in parallel (with races).  These two
> patches separate the targets with the same dependencies and prevent
> these races.  I would actually consider this to be a bug in make, but
> that is another story.
Nope, consider the command to execute was: touch $@ - then it make all
sense again.

	Sam

===== drivers/scsi/aic7xxx/Makefile 1.21 vs edited =====
--- 1.21/drivers/scsi/aic7xxx/Makefile	Fri May  2 20:04:40 2003
+++ edited/drivers/scsi/aic7xxx/Makefile	Fri Sep  5 21:14:01 2003
@@ -58,7 +58,13 @@
 	-p $(obj)/aic7xxx_reg_print.c -i aic7xxx_osm.h
 
 ifeq ($(CONFIG_AIC7XXX_BUILD_FIRMWARE),y)
-$(aic7xxx-gen-y): $(src)/aic7xxx.seq $(src)/aic7xxx.reg $(obj)/aicasm/aicasm
+$(aic7xxx-gen-y): $(src)/aic7xxx.seq $(src)/aic7xxx.reg
+$(aic7xxx-gen-y): doaic7xasm
+
+.PHONY: doaic7xasm
+$(aic7xxx-gen-y): doaic7xasm
+
+doaic7xasm: $(obj)/aicasm/aicasm
 	$(obj)/aicasm/aicasm -I$(src) -r $(obj)/aic7xxx_reg.h \
 			      $(aicasm-7xxx-opts-y) -o $(obj)/aic7xxx_seq.h \
 			      $(src)/aic7xxx.seq
@@ -72,7 +78,12 @@
 	-p $(obj)/aic79xx_reg_print.c -i aic79xx_osm.h
 
 ifeq ($(CONFIG_AIC79XX_BUILD_FIRMWARE),y)
-$(aic79xx-gen-y): $(src)/aic79xx.seq $(src)/aic79xx.reg $(obj)/aicasm/aicasm
+$(aic79xx-gen-y): $(src)/aic79xx.seq $(src)/aic79xx.reg
+
+.PHONY: doaic79asm
+$(aic79xx-gen-y): doaic79asm
+
+doaic79asm: $(obj)/aicasm/aicasm
 	$(obj)/aicasm/aicasm -I$(src) -r $(obj)/aic79xx_reg.h \
 			      $(aicasm-79xx-opts-y) -o $(obj)/aic79xx_seq.h \
 			      $(src)/aic79xx.seq
===== drivers/scsi/aic7xxx/aicasm/Makefile 1.11 vs edited =====
--- 1.11/drivers/scsi/aic7xxx/aicasm/Makefile	Tue Mar 11 01:57:17 2003
+++ edited/drivers/scsi/aic7xxx/aicasm/Makefile	Fri Sep  5 21:02:54 2003
@@ -49,14 +49,18 @@
 clean:
 	rm -f $(clean-files)
 
-aicasm_gram.c aicasm_gram.h: aicasm_gram.y
+aicasm_gram.c: aicasm_gram.h 
+	mv $(<:.h=).tab.c $(<:.h=.c)
+
+aicasm_gram.h: aicasm_gram.y
 	$(YACC) $(YFLAGS) -b $(<:.y=) $<
-	mv $(<:.y=).tab.c $(<:.y=.c)
 	mv $(<:.y=).tab.h $(<:.y=.h)
 
-aicasm_macro_gram.c aicasm_macro_gram.h: aicasm_macro_gram.y
+aicasm_macro_gram.c: aicasm_macro_gram.h
+	mv $(<:.h=).tab.c $(<:.h=.c)
+
+aicasm_macro_gram.h: aicasm_macro_gram.y
 	$(YACC) $(YFLAGS) -b $(<:.y=) -p mm $<
-	mv $(<:.y=).tab.c $(<:.y=.c)
 	mv $(<:.y=).tab.h $(<:.y=.h)
 
 aicasm_scan.c: aicasm_scan.l