[Xen-devel] [PATCH] Makefile targets generating several files at once

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

In a few places in the tree the Makefiles have constructs like this:
   one_file another_file:
       $(COMMAND_WHICH_GENERATES_BOTH_AT_ONCE)
This is wrong, because make will run _two copies_ of the same command
at once.  This generally causes races and hard-to-reproduce build
failures.

Notably, `make -j4' at the top level will build stubdom libxc twice
simultaneously!

In this patch we replace the occurrences of this construct with the
correct idiom:
   one_file: another_file
   another_file:
       $(COMMAND_WHICH_GENERATES_BOTH_AT_ONCE)

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>

diff -r b8d2a4134a68 stubdom/Makefile
--- a/stubdom/Makefile  Wed Mar 03 17:41:58 2010 +0000
+++ b/stubdom/Makefile  Fri Mar 05 11:53:37 2010 +0000
@@ -265,8 +265,10 @@
 
 .PHONY: libxc
 libxc: libxc-$(XEN_TARGET_ARCH)/libxenctrl.a 
libxc-$(XEN_TARGET_ARCH)/libxenguest.a
-libxc-$(XEN_TARGET_ARCH)/libxenctrl.a libxc-$(XEN_TARGET_ARCH)/libxenguest.a:: 
cross-zlib
+libxc-$(XEN_TARGET_ARCH)/libxenctrl.a: cross-zlib
        CPPFLAGS="$(TARGET_CPPFLAGS)" CFLAGS="$(TARGET_CFLAGS)" $(MAKE) -C 
libxc-$(XEN_TARGET_ARCH)
+
+ libxc-$(XEN_TARGET_ARCH)/libxenguest.a: libxc-$(XEN_TARGET_ARCH)/libxenctrl.a
 
 #######
 # ioemu
diff -r b8d2a4134a68 tools/flask/policy/Makefile
--- a/tools/flask/policy/Makefile       Wed Mar 03 17:41:58 2010 +0000
+++ b/tools/flask/policy/Makefile       Fri Mar 05 11:53:37 2010 +0000
@@ -166,7 +166,8 @@
 #
 # Load the binary policy
 #
-reload tmp/load: $(LOADPATH) $(FCPATH)
+tmp/load: reload
+reload: $(LOADPATH) $(FCPATH)
        @echo "Loading $(NAME) $(LOADPATH)"
        $(QUIET) $(LOADPOLICY) $(LOADPATH)
        @touch tmp/load
@@ -205,7 +206,8 @@
 # extract attributes and put them first. extract post te stuff
 # like genfscon and put last.  portcon, nodecon, and netifcon
 # is delayed since they are generated by m4
-tmp/all_attrs_types.conf tmp/only_te_rules.conf tmp/all_post.conf: 
tmp/all_te_files.conf tmp/post_te_files.conf
+tmp/all_attrs_types.conf tmp/all_post.conf: tmp/only_te_rules.conf
+tmp/only_te_rules.conf: tmp/all_te_files.conf tmp/post_te_files.conf
        $(QUIET) grep ^attribute tmp/all_te_files.conf > 
tmp/all_attrs_types.conf || true
        $(QUIET) grep '^type ' tmp/all_te_files.conf >> tmp/all_attrs_types.conf
        $(QUIET) cat tmp/post_te_files.conf > tmp/all_post.conf
diff -r b8d2a4134a68 tools/xenstat/libxenstat/Makefile
--- a/tools/xenstat/libxenstat/Makefile Wed Mar 03 17:41:58 2010 +0000
+++ b/tools/xenstat/libxenstat/Makefile Fri Mar 05 11:53:37 2010 +0000
@@ -107,7 +107,8 @@
 # Python bindings
 PYTHON_VERSION=2.3
 PYTHON_FLAGS=-I/usr/include/python$(PYTHON_VERSION) -lpython$(PYTHON_VERSION)
-$(PYSRC) $(PYMOD): bindings/swig/xenstat.i
+$(PYMOD): $(PYSRC)
+$(PYSRC): bindings/swig/xenstat.i
        swig -python $(SWIG_FLAGS) -outdir $(@D) -o $(PYSRC) $<
 
 $(PYLIB): $(PYSRC)
@@ -128,7 +129,8 @@
 
 # Perl bindings
 PERL_FLAGS=`perl -MConfig -e 'print "$$Config{ccflags} 
-I$$Config{archlib}/CORE";'`
-$(PERLSRC) $(PERLMOD): bindings/swig/xenstat.i
+$(PERLMOD): $(PERLSRC)
+$(PERLSRC): bindings/swig/xenstat.i
        swig -perl $(SWIG_FLAGS) -outdir $(@D) -o $(PERLSRC) $<
 
 $(PERLLIB): $(PERLSRC)

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