Fix qapi code generation wrt parallel build

Make's multiple output syntax

  x.c x.h: x.template
       gen < x.template

actually invokes the command once for x.c and once for x.h (with differing $@
in each invocation).  During a parallel build, the two commands may be invoked
in parallel; this opens up a race, where the second invocation trashes a file
supposedly produced during the first, and now in use by a dependent command.

The various qapi code generators are susceptible to this; fix by making them
generate just one file per invocation.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 11 insertions, 9 deletions

diff --git a/Makefile b/Makefile
index 368eeae9b0..0838bc4474 100644
--- a/Makefile
+++ b/Makefile
@@ -173,35 +173,37 @@ qapi-dir := $(BUILD_DIR)/qapi-generated
 test-qmp-input-visitor.o test-qmp-output-visitor.o test-qmp-commands.o qemu-ga$(EXESUF): QEMU_CFLAGS += -I $(qapi-dir)
 qemu-ga$(EXESUF): LIBS = $(LIBS_QGA)
 
+gen-out-type = $(subst .,-,$@)
+
 $(qapi-dir)/test-qapi-types.c $(qapi-dir)/test-qapi-types.h :\
 $(SRC_PATH)/qapi-schema-test.json $(SRC_PATH)/scripts/qapi-types.py
-	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-types.py -o "$(qapi-dir)" -p "test-" < $<, "  GEN   $@")
+	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-types.py $(gen-out-type) -o "$(qapi-dir)" -p "test-" < $<, "  GEN   $@")
 $(qapi-dir)/test-qapi-visit.c $(qapi-dir)/test-qapi-visit.h :\
 $(SRC_PATH)/qapi-schema-test.json $(SRC_PATH)/scripts/qapi-visit.py
-	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-visit.py -o "$(qapi-dir)" -p "test-" < $<, "  GEN   $@")
+	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-visit.py $(gen-out-type) -o "$(qapi-dir)" -p "test-" < $<, "  GEN   $@")
 $(qapi-dir)/test-qmp-commands.h $(qapi-dir)/test-qmp-marshal.c :\
 $(SRC_PATH)/qapi-schema-test.json $(SRC_PATH)/scripts/qapi-commands.py
-	    $(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-commands.py -o "$(qapi-dir)" -p "test-" < $<, "  GEN   $@")
+	    $(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-commands.py $(gen-out-type) -o "$(qapi-dir)" -p "test-" < $<, "  GEN   $@")
 
 $(qapi-dir)/qga-qapi-types.c $(qapi-dir)/qga-qapi-types.h :\
 $(SRC_PATH)/qapi-schema-guest.json $(SRC_PATH)/scripts/qapi-types.py
-	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-types.py -o "$(qapi-dir)" -p "qga-" < $<, "  GEN   $@")
+	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-types.py $(gen-out-type) -o "$(qapi-dir)" -p "qga-" < $<, "  GEN   $@")
 $(qapi-dir)/qga-qapi-visit.c $(qapi-dir)/qga-qapi-visit.h :\
 $(SRC_PATH)/qapi-schema-guest.json $(SRC_PATH)/scripts/qapi-visit.py
-	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-visit.py -o "$(qapi-dir)" -p "qga-" < $<, "  GEN   $@")
+	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-visit.py $(gen-out-type) -o "$(qapi-dir)" -p "qga-" < $<, "  GEN   $@")
 $(qapi-dir)/qga-qmp-commands.h $(qapi-dir)/qga-qmp-marshal.c :\
 $(SRC_PATH)/qapi-schema-guest.json $(SRC_PATH)/scripts/qapi-commands.py
-	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-commands.py -o "$(qapi-dir)" -p "qga-" < $<, "  GEN   $@")
+	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-commands.py $(gen-out-type) -o "$(qapi-dir)" -p "qga-" < $<, "  GEN   $@")
 
 qapi-types.c qapi-types.h :\
 $(SRC_PATH)/qapi-schema.json $(SRC_PATH)/scripts/qapi-types.py
-	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-types.py -o "." < $<, "  GEN   $@")
+	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-types.py $(gen-out-type) -o "." < $<, "  GEN   $@")
 qapi-visit.c qapi-visit.h :\
 $(SRC_PATH)/qapi-schema.json $(SRC_PATH)/scripts/qapi-visit.py
-	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-visit.py -o "."  < $<, "  GEN   $@")
+	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-visit.py $(gen-out-type) -o "."  < $<, "  GEN   $@")
 qmp-commands.h qmp-marshal.c :\
 $(SRC_PATH)/qapi-schema.json $(SRC_PATH)/scripts/qapi-commands.py
-	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-commands.py -m -o "." < $<, "  GEN   $@")
+	$(call quiet-command,$(PYTHON) $(SRC_PATH)/scripts/qapi-commands.py $(gen-out-type) -m -o "." < $<, "  GEN   $@")
 
 test-qmp-output-visitor.o: $(addprefix $(qapi-dir)/, test-qapi-types.c test-qapi-types.h test-qapi-visit.c test-qapi-visit.h) $(qapi-obj-y)
 test-qmp-output-visitor: test-qmp-output-visitor.o $(qobject-obj-y) $(qapi-obj-y) $(tools-obj-y) $(qapi-dir)/test-qapi-visit.o $(qapi-dir)/test-qapi-types.o