[PATCH v4 3/3] meson: generate trace events for qmp commands

[Vladimir Sementsov-Ogievskiy]

1. Add --no-trace-events to suppress trace events generation in some
   cases, and make trace events be generated by default.
2. Add corresponding .trace-events files as outputs in qapi_files
   custom target
3. Define global qapi_trace_events list of .trace-events file targets,
   to fill in trace/qapi.build and to use in trace/meson.build
4. In trace/meson.build use the new array as an additional source of
   .trace_events files to be processed

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 docs/devel/qapi-code-gen.rst | 23 +++++++++++++++++++++--
 meson.build                  |  3 +++
 qapi/meson.build             |  7 +++++++
 qga/meson.build              | 11 ++++++++++-
 scripts/qapi/main.py         | 10 +++++++---
 tests/meson.build            | 11 ++++++++++-
 trace/meson.build            | 11 ++++++++---
 7 files changed, 66 insertions(+), 10 deletions(-)

diff --git a/docs/devel/qapi-code-gen.rst b/docs/devel/qapi-code-gen.rst
index a3b5473089..a3430740bd 100644
--- a/docs/devel/qapi-code-gen.rst
+++ b/docs/devel/qapi-code-gen.rst
@@ -1619,7 +1619,10 @@ Code generated for commands
 
 These are the marshaling/dispatch functions for the commands defined
 in the schema.  The generated code provides qmp_marshal_COMMAND(), and
-declares qmp_COMMAND() that the user must implement.
+declares qmp_COMMAND() that the user must implement.  The generated code
+contains trace events code.  Corresponding .trace-events file with list
+of trace events is generated too, and should be parsed by trace generator
+later to generate trace event code, see `tracing <tracing.html>`.
 
 The following files are generated:
 
@@ -1630,6 +1633,9 @@ The following files are generated:
  ``$(prefix)qapi-commands.h``
      Function prototypes for the QMP commands specified in the schema
 
+ ``$(prefix)qapi-commands.trace-events``
+     Trace events file for trace generator, see `tracing <tracing.html>`.
+
  ``$(prefix)qapi-init-commands.h``
      Command initialization prototype
 
@@ -1689,14 +1695,27 @@ Example::
             goto out;
         }
 
+        if (trace_event_get_state_backends(TRACE_QMP_ENTER_MY_COMMAND)) {
+            g_autoptr(GString) req_json = qobject_to_json(QOBJECT(args));
+
+            trace_qmp_enter_my_command(req_json->str);
+        }
+
         retval = qmp_my_command(arg.arg1, &err);
-        error_propagate(errp, err);
         if (err) {
+            trace_qmp_exit_my_command(error_get_pretty(err), false);
+            error_propagate(errp, err);
             goto out;
         }
 
         qmp_marshal_output_UserDefOne(retval, ret, errp);
 
+        if (trace_event_get_state_backends(TRACE_QMP_EXIT_MY_COMMAND)) {
+            g_autoptr(GString) ret_json = qobject_to_json(*ret);
+
+            trace_qmp_exit_my_command(ret_json->str, true);
+        }
+
     out:
         visit_free(v);
         v = qapi_dealloc_visitor_new();
diff --git a/meson.build b/meson.build
index 833fd6bc4c..e0cfafe8d9 100644
--- a/meson.build
+++ b/meson.build
@@ -41,6 +41,7 @@ qemu_icondir = get_option('datadir') / 'icons'
 
 config_host_data = configuration_data()
 genh = []
+qapi_trace_events = []
 
 target_dirs = config_host['TARGET_DIRS'].split()
 have_linux_user = false
@@ -2557,6 +2558,8 @@ if 'CONFIG_VHOST_USER' in config_host
   vhost_user = libvhost_user.get_variable('vhost_user_dep')
 endif
 
+# NOTE: the trace/ subdirectory needs the qapi_trace_events variable
+# that is filled in by qapi/.
 subdir('qapi')
 subdir('qobject')
 subdir('stubs')
diff --git a/qapi/meson.build b/qapi/meson.build
index c0c49c15e4..656ef0e039 100644
--- a/qapi/meson.build
+++ b/qapi/meson.build
@@ -114,6 +114,7 @@ foreach module : qapi_all_modules
       'qapi-events-@0@.h'.format(module),
       'qapi-commands-@0@.c'.format(module),
       'qapi-commands-@0@.h'.format(module),
+      'qapi-commands-@0@.trace-events'.format(module),
     ]
   endif
   if module.endswith('-target')
@@ -137,6 +138,9 @@ foreach output : qapi_util_outputs
   if output.endswith('.h')
     genh += qapi_files[i]
   endif
+  if output.endswith('.trace-events')
+    qapi_trace_events += qapi_files[i]
+  endif
   util_ss.add(qapi_files[i])
   i = i + 1
 endforeach
@@ -145,6 +149,9 @@ foreach output : qapi_specific_outputs + 
qapi_nonmodule_outputs
   if output.endswith('.h')
     genh += qapi_files[i]
   endif
+  if output.endswith('.trace-events')
+    qapi_trace_events += qapi_files[i]
+  endif
   specific_ss.add(when: 'CONFIG_SOFTMMU', if_true: qapi_files[i])
   i = i + 1
 endforeach
diff --git a/qga/meson.build b/qga/meson.build
index cfb1fbc085..1f2818a1b9 100644
--- a/qga/meson.build
+++ b/qga/meson.build
@@ -15,10 +15,19 @@ qga_qapi_outputs = [
   'qga-qapi-visit.h',
 ]
 
+# We don't generate trace-events, just because it's not simple. For do it,
+# we also should add .trace-events file into qga_qapi_outputs, and than
+# add corresponding element of qga_qapi_files into qapi_trace_events
+# global list, which is processed than in trace/meson.build.
+# This means, that we'll have to move subdir('qga') above subdir('trace')
+# in root meson.build. But that in turn will break the dependency of
+# qga on qemuutil (which depends on trace_ss).
+# So, resolving these dependencies and drop --no-trace-events is a TODO.
 qga_qapi_files = custom_target('QGA QAPI files',
                                output: qga_qapi_outputs,
                                input: 'qapi-schema.json',
-                               command: [ qapi_gen, '-o', 'qga', '-p', 'qga-', 
'@INPUT0@' ],
+                               command: [ qapi_gen, '-o', 'qga', '-p', 'qga-', 
'@INPUT0@',
+                                          '--no-trace-events' ],
                                depend_files: qapi_gen_depends)
 
 qga_ss = ss.source_set()
diff --git a/scripts/qapi/main.py b/scripts/qapi/main.py
index 2e61409f04..d53e5b800c 100644
--- a/scripts/qapi/main.py
+++ b/scripts/qapi/main.py
@@ -32,7 +32,8 @@ def generate(schema_file: str,
              output_dir: str,
              prefix: str,
              unmask: bool = False,
-             builtins: bool = False) -> None:
+             builtins: bool = False,
+             add_trace_events: bool = False) -> None:
     """
     Generate C code for the given schema into the target directory.
 
@@ -49,7 +50,7 @@ def generate(schema_file: str,
     schema = QAPISchema(schema_file)
     gen_types(schema, output_dir, prefix, builtins)
     gen_visit(schema, output_dir, prefix, builtins)
-    gen_commands(schema, output_dir, prefix, False)
+    gen_commands(schema, output_dir, prefix, add_trace_events)
     gen_events(schema, output_dir, prefix)
     gen_introspect(schema, output_dir, prefix, unmask)
 
@@ -74,6 +75,8 @@ def main() -> int:
     parser.add_argument('-u', '--unmask-non-abi-names', action='store_true',
                         dest='unmask',
                         help="expose non-ABI names in introspection")
+    parser.add_argument('--no-trace-events', action='store_true',
+                        help="suppress adding trace events to qmp marshals")
     parser.add_argument('schema', action='store')
     args = parser.parse_args()
 
@@ -88,7 +91,8 @@ def main() -> int:
                  output_dir=args.output_dir,
                  prefix=args.prefix,
                  unmask=args.unmask,
-                 builtins=args.builtins)
+                 builtins=args.builtins,
+                 add_trace_events=not args.no_trace_events)
     except QAPIError as err:
         print(f"{sys.argv[0]}: {str(err)}", file=sys.stderr)
         return 1
diff --git a/tests/meson.build b/tests/meson.build
index 3f3882748a..b4b95cc198 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -31,13 +31,22 @@ test_qapi_outputs = [
   'test-qapi-visit.h',
 ]
 
+# We don't generate trace-events, just because it's not simple. For do it,
+# we also should add .trace-events file into test_qapi_outputs, and than
+# add corresponding element of test_qapi_files into qapi_trace_events
+# global list, which is processed than in trace/meson.build.
+# This means, that we'll have to move subdir('tests') above subdir('trace')
+# in root meson.build. But that in turn will break the dependency of
+# tests on qemuutil (which depends on trace_ss).
+# So, resolving these dependencies and drop --no-trace-events is a TODO.
 test_qapi_files = custom_target('Test QAPI files',
                                 output: test_qapi_outputs,
                                 input: 
files('qapi-schema/qapi-schema-test.json',
                                              
'qapi-schema/include/sub-module.json',
                                              
'qapi-schema/sub-sub-module.json'),
                                 command: [ qapi_gen, '-o', 
meson.current_build_dir(),
-                                           '-b', '-p', 'test-', '@INPUT0@' ],
+                                           '-b', '-p', 'test-', '@INPUT0@',
+                                           '--no-trace-events' ],
                                 depend_files: qapi_gen_depends)
 
 # meson doesn't like generated output in other directories
diff --git a/trace/meson.build b/trace/meson.build
index 573dd699c6..c4794a1f2a 100644
--- a/trace/meson.build
+++ b/trace/meson.build
@@ -2,10 +2,15 @@
 specific_ss.add(files('control-target.c'))
 
 trace_events_files = []
-foreach dir : [ '.' ] + trace_events_subdirs
-  trace_events_file = meson.project_source_root() / dir / 'trace-events'
+foreach item : [ '.' ] + trace_events_subdirs + qapi_trace_events
+  if item in qapi_trace_events
+    trace_events_file = item
+    group_name = item.full_path().split('/')[-1].underscorify()
+  else
+    trace_events_file = meson.project_source_root() / item / 'trace-events'
+    group_name = item == '.' ? 'root' : item.underscorify()
+  endif
   trace_events_files += [ trace_events_file ]
-  group_name = dir == '.' ? 'root' : dir.underscorify()
   group = '--group=' + group_name
   fmt = '@0@-' + group_name + '.@1@'
 
-- 
2.31.1