revng.daemon: prevent shutdown crash

Change the behavior of `revng daemon` to avoid a crash at shutdown
caused by `rp_shutdown` not being called due to the pointer of
`rp_manager` not being freed.

python/revng/api/_capi.py

@@ -16,6 +16,12 @@ from revng.support import AnyPaths, get_root, to_iterable
 from revng.support.collect import collect_files, collect_libraries, collect_one
 
 
+# This counter is used to count the pointers released by PipelineC, since
+# calling rp_shutdown before all pointers are freed leads to a crash
+# This will count (atomically) the pointers created by PipelineC and decrements
+# once the pointer is freed by `ffi.gc`. Once the API signals that it will no
+# longer do anything (by calling `mark_end`) then once the counter reaches 0
+# the callback can be invoked which will safely call rp_shutdown.
 class AtomicCounterWithCallback:
     """Simple atomic counter, will call callback once mark_end has been called
     and the counter reaches zero"""
@@ -39,6 +45,8 @@ class AtomicCounterWithCallback:
     def mark_end(self):
         with self.lock:
             self.ending = True
+            if self.counter == 0:
+                self.callback()
 
 
 class ApiWrapper:

python/revng/api/analysis.py

@@ -75,7 +75,7 @@ class AnalysesList(Sequence[Analysis]):
         return _api.rp_analyses_list_count(self._analyses_list)
 
     def _get_analysis(self, index: int) -> Analysis:
-        _analysis = _api.rp_manager_get_analysis(self._manager, self._analyses_list, index)
+        _analysis = _api.rp_manager_get_analysis(self._manager._manager, self._analyses_list, index)
         return Analysis(_analysis)
 
     @overload

python/revng/api/manager.py

@@ -427,7 +427,7 @@ class Manager:
 
     def _analyses_list_get(self, index: int) -> AnalysesList:
         _analyses_list = _api.rp_manager_get_analyses_list(self._manager, index)
-        return AnalysesList(_analyses_list, self._manager)
+        return AnalysesList(_analyses_list, self)
 
     def analyses_lists(self) -> Generator[AnalysesList, None, None]:
         return make_generator(self._analyses_list_count(), self._analyses_list_get)

python/revng/daemon/__init__.py

@@ -105,7 +105,7 @@ def make_startlette() -> Starlette:
         }
 
     routes = [
-        Route("/", generate_demo_page(manager, DEBUG), methods=["GET"]),
+        Route("/", generate_demo_page(manager.workdir, DEBUG), methods=["GET"]),
         Route("/status", status, methods=["GET"]),
         Mount(
             "/graphql",
@@ -129,6 +129,7 @@ def make_startlette() -> Starlette:
         store_result = manager.save()
         if not store_result:
             logging.warning("Failed to store manager's containers")
+        manager._manager = None
         capi_shutdown()
 
     return Starlette(

python/revng/daemon/demo_webpage.py

@@ -8,18 +8,16 @@ from starlette.requests import Request
 from starlette.responses import PlainTextResponse
 from starlette.templating import Jinja2Templates
 
-from revng.api import Manager
-
 module_dir = Path(__file__).parent.resolve()
 templates = Jinja2Templates(directory=module_dir / "templates")
 
 
-def generate_demo_page(manager: Manager, debug: bool):
+def generate_demo_page(workdir: Path, debug: bool):
     if debug:
 
         async def dev_demo_page(request: Request):
             return templates.TemplateResponse(
-                "index.html", {"request": request, "manager": manager}
+                "index.html", {"request": request, "workdir": workdir}
             )
 
         return dev_demo_page

python/revng/daemon/templates/index.html

@@ -9,7 +9,7 @@
     </div>
     <div>
         Welcome to revng!<br />
-        Working directory is {{ manager.workdir }}
+        Working directory is {{ workdir }}
     </div>
 
     <div>