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Re: [Qemu-devel] [PATCH] Fix qapi code generation wrt parallel build

From: Anthony Liguori
Subject: Re: [Qemu-devel] [PATCH] Fix qapi code generation wrt parallel build
Date: Tue, 27 Dec 2011 10:37:19 -0600
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.23) Gecko/20110922 Lightning/1.0b2 Thunderbird/3.1.15 
On 12/27/2011 08:02 AM, Avi Kivity wrote:

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<address@hidden>


Applied.  Thanks.

Regards,

Anthony Liguori


---
  Makefile                 |   20 +++++++++++---------
  scripts/qapi-commands.py |   30 +++++++++++++++++++++++++++---
  scripts/qapi-types.py    |   27 ++++++++++++++++++++++++---
  scripts/qapi-visit.py    |   27 ++++++++++++++++++++++++---
  4 files changed, 86 insertions(+), 18 deletions(-)

diff --git a/Makefile b/Makefile
index 2c03055..5958289 100644
--- a/Makefile
+++ b/Makefile
@@ -172,35 +172,37 @@ 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
diff --git a/scripts/qapi-commands.py b/scripts/qapi-commands.py
index 54d1f5d..bd7b207 100644
--- a/scripts/qapi-commands.py
+++ b/scripts/qapi-commands.py
@@ -372,7 +372,9 @@ def gen_command_def_prologue(prefix="", proxy=False):


  try:
-    opts, args = getopt.gnu_getopt(sys.argv[1:], "p:o:m", ["prefix=", "output-dir=", 
"type=", "middle"])
+    opts, args = getopt.gnu_getopt(sys.argv[1:], "chp:o:m",
+                                   ["source", "header", "prefix=",
+                                    "output-dir=", "type=", "middle"])
  except getopt.GetoptError, err:
      print str(err)
      sys.exit(1)
@@ -384,6 +386,9 @@ c_file = 'qmp-marshal.c'
  h_file = 'qmp-commands.h'
  middle_mode = False

+do_c = False
+do_h = False
+
  for o, a in opts:
      if o in ("-p", "--prefix"):
          prefix = a
@@ -393,10 +398,29 @@ for o, a in opts:
          dispatch_type = a
      elif o in ("-m", "--middle"):
          middle_mode = True
+    elif o in ("-c", "--source"):
+        do_h = True
+    elif o in ("-h", "--header"):
+        do_c = True
+
+if not do_c and not do_h:
+    do_c = True
+    do_h = True

  c_file = output_dir + prefix + c_file
  h_file = output_dir + prefix + h_file

+def maybe_open(really, name, opt):
+    class Null(object):
+        def write(self, str):
+            pass
+        def read(self):
+            return ''
+    if really:
+        return open(name, opt)
+    else:
+        return Null()
+
  try:
      os.makedirs(output_dir)
  except os.error, e:
@@ -408,8 +432,8 @@ commands = filter(lambda expr: expr.has_key('command'), 
exprs)
  commands = filter(lambda expr: not expr.has_key('gen'), commands)

  if dispatch_type == "sync":
-    fdecl = open(h_file, 'w')
-    fdef = open(c_file, 'w')
+    fdecl = maybe_open(do_h, h_file, 'w')
+    fdef = maybe_open(do_c, c_file, 'w')
      ret = gen_command_decl_prologue(header=basename(h_file), 
guard=guardname(h_file), prefix=prefix)
      fdecl.write(ret)
      ret = gen_command_def_prologue(prefix=prefix)
diff --git a/scripts/qapi-types.py b/scripts/qapi-types.py
index 267cb49..ae644bc 100644
--- a/scripts/qapi-types.py
+++ b/scripts/qapi-types.py
@@ -163,7 +163,8 @@ void qapi_free_%(type)s(%(c_type)s obj)


  try:
-    opts, args = getopt.gnu_getopt(sys.argv[1:], "p:o:", ["prefix=", 
"output-dir="])
+    opts, args = getopt.gnu_getopt(sys.argv[1:], "chp:o:",
+                                   ["source", "header", "prefix=", 
"output-dir="])
  except getopt.GetoptError, err:
      print str(err)
      sys.exit(1)
@@ -173,11 +174,22 @@ prefix = ""
  c_file = 'qapi-types.c'
  h_file = 'qapi-types.h'

+do_c = False
+do_h = False
+
  for o, a in opts:
      if o in ("-p", "--prefix"):
          prefix = a
      elif o in ("-o", "--output-dir"):
          output_dir = a + "/"
+    elif o in ("-c", "--source"):
+        do_h = True
+    elif o in ("-h", "--header"):
+        do_c = True
+
+if not do_c and not do_h:
+    do_c = True
+    do_h = True

  c_file = output_dir + prefix + c_file
  h_file = output_dir + prefix + h_file
@@ -188,8 +200,17 @@ except os.error, e:
      if e.errno != errno.EEXIST:
          raise

-fdef = open(c_file, 'w')
-fdecl = open(h_file, 'w')
+def maybe_open(really, name, opt):
+    class Null(object):
+        def write(self, str):
+            pass
+        def read(self):
+            return ''
+    if really:
+        return open(name, opt)
+
+fdef = maybe_open(do_c, c_file, 'w')
+fdecl = maybe_open(do_h, h_file, 'w')

  fdef.write(mcgen('''
  /* AUTOMATICALLY GENERATED, DO NOT MODIFY */
diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
index 62de83d..e9d0584 100644
--- a/scripts/qapi-visit.py
+++ b/scripts/qapi-visit.py
@@ -139,7 +139,8 @@ void visit_type_%(name)s(Visitor *m, %(name)s * obj, const 
char *name, Error **e
                  name=name)

  try:
-    opts, args = getopt.gnu_getopt(sys.argv[1:], "p:o:", ["prefix=", 
"output-dir="])
+    opts, args = getopt.gnu_getopt(sys.argv[1:], "chp:o:",
+                                   ["source", "header", "prefix=", 
"output-dir="])
  except getopt.GetoptError, err:
      print str(err)
      sys.exit(1)
@@ -149,11 +150,22 @@ prefix = ""
  c_file = 'qapi-visit.c'
  h_file = 'qapi-visit.h'

+do_c = False
+do_h = False
+
  for o, a in opts:
      if o in ("-p", "--prefix"):
          prefix = a
      elif o in ("-o", "--output-dir"):
          output_dir = a + "/"
+    elif o in ("-c", "--source"):
+        do_h = True
+    elif o in ("-h", "--header"):
+        do_c = True
+
+if not do_c and not do_h:
+    do_c = True
+    do_h = True

  c_file = output_dir + prefix + c_file
  h_file = output_dir + prefix + h_file
@@ -164,8 +176,17 @@ except os.error, e:
      if e.errno != errno.EEXIST:
          raise

-fdef = open(c_file, 'w')
-fdecl = open(h_file, 'w')
+def maybe_open(really, name, opt):
+    class Null(object):
+        def write(self, str):
+            pass
+        def read(self):
+            return ''
+    if really:
+        return open(name, opt)
+
+fdef = maybe_open(do_c, c_file, 'w')
+fdecl = maybe_open(do_h, h_file, 'w')

  fdef.write(mcgen('''
  /* THIS FILE IS AUTOMATICALLY GENERATED, DO NOT MODIFY */
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