From 971db5e21e35e1ad0d124b954ce13d463b887b6c Mon Sep 17 00:00:00 2001 From: Tom Tromey Date: Sat, 8 Jun 2019 08:15:57 -0600 Subject: [PATCH] Use run_on_main_thread in gdb.post_event This changes gdb.post_event to use the new run_on_main_thread function. This is somewhat tricky because the Python GIL must be held while manipulating reference counts. 2019-11-26 Tom Tromey * python/python.c (class gdbpy_gil): New. (struct gdbpy_event): Add constructor, destructor, operator(). (gdbpy_post_event): Use run_on_main_thread. (gdbpy_initialize_events): Remove. (do_start_initialization): Update. Change-Id: Ie4431e60f328dae48bd96b6c6a8e875e70bda1de --- gdb/ChangeLog | 8 +++ gdb/python/python.c | 135 +++++++++++++++++++++----------------------- 2 files changed, 71 insertions(+), 72 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index 289cbce640b..0c5aab26d30 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,11 @@ +2019-11-26 Tom Tromey + + * python/python.c (class gdbpy_gil): New. + (struct gdbpy_event): Add constructor, destructor, operator(). + (gdbpy_post_event): Use run_on_main_thread. + (gdbpy_initialize_events): Remove. + (do_start_initialization): Update. + 2019-11-26 Tom Tromey * NEWS: Add entry. diff --git a/gdb/python/python.c b/gdb/python/python.c index 1cc5ebb7a73..2f4fb0fe10d 100644 --- a/gdb/python/python.c +++ b/gdb/python/python.c @@ -28,14 +28,13 @@ #include "value.h" #include "language.h" #include "event-loop.h" -#include "serial.h" #include "readline/tilde.h" #include "python.h" #include "extension-priv.h" #include "cli/cli-utils.h" #include #include "location.h" -#include "ser-event.h" +#include "run-on-main-thread.h" /* Declared constants and enum for python stack printing. */ static const char python_excp_none[] = "none"; @@ -940,63 +939,81 @@ gdbpy_source_script (const struct extension_language_defn *extlang, /* Posting and handling events. */ +/* A helper class to save and restore the GIL, but without touching + the other globals that are handled by gdbpy_enter. */ + +class gdbpy_gil +{ +public: + + gdbpy_gil () + : m_state (PyGILState_Ensure ()) + { + } + + ~gdbpy_gil () + { + PyGILState_Release (m_state); + } + + DISABLE_COPY_AND_ASSIGN (gdbpy_gil); + +private: + + PyGILState_STATE m_state; +}; + /* A single event. */ struct gdbpy_event { - /* The Python event. This is just a callable object. */ - PyObject *event; - /* The next event. */ - struct gdbpy_event *next; -}; + gdbpy_event (gdbpy_ref<> &&func) + : m_func (func.release ()) + { + } -/* All pending events. */ -static struct gdbpy_event *gdbpy_event_list; -/* The final link of the event list. */ -static struct gdbpy_event **gdbpy_event_list_end; + gdbpy_event (gdbpy_event &&other) + : m_func (other.m_func) + { + other.m_func = nullptr; + } -/* So that we can wake up the main thread even when it is blocked in - poll(). */ -static struct serial_event *gdbpy_serial_event; + gdbpy_event (const gdbpy_event &other) + : m_func (other.m_func) + { + gdbpy_gil gil; + Py_XINCREF (m_func); + } + + ~gdbpy_event () + { + gdbpy_gil gil; + Py_XDECREF (m_func); + } -/* The file handler callback. This reads from the internal pipe, and - then processes the Python event queue. This will always be run in - the main gdb thread. */ + gdbpy_event &operator= (const gdbpy_event &other) = delete; -static void -gdbpy_run_events (int error, gdb_client_data client_data) -{ - gdbpy_enter enter_py (get_current_arch (), current_language); + void operator() () + { + gdbpy_enter enter_py (get_current_arch (), current_language); - /* Clear the event fd. Do this before flushing the events list, so - that any new event post afterwards is sure to re-awake the event - loop. */ - serial_event_clear (gdbpy_serial_event); + gdbpy_ref<> call_result (PyObject_CallObject (m_func, NULL)); + if (call_result == NULL) + gdbpy_print_stack (); + } - while (gdbpy_event_list) - { - /* Dispatching the event might push a new element onto the event - loop, so we update here "atomically enough". */ - struct gdbpy_event *item = gdbpy_event_list; - gdbpy_event_list = gdbpy_event_list->next; - if (gdbpy_event_list == NULL) - gdbpy_event_list_end = &gdbpy_event_list; - - gdbpy_ref<> call_result (PyObject_CallObject (item->event, NULL)); - if (call_result == NULL) - gdbpy_print_stack (); +private: - Py_DECREF (item->event); - xfree (item); - } -} + /* The Python event. This is just a callable object. Note that + this is not a gdbpy_ref<>, because we have to take particular + care to only destroy the reference when holding the GIL. */ + PyObject *m_func; +}; /* Submit an event to the gdb thread. */ static PyObject * gdbpy_post_event (PyObject *self, PyObject *args) { - struct gdbpy_event *event; PyObject *func; - int wakeup; if (!PyArg_ParseTuple (args, "O", &func)) return NULL; @@ -1008,38 +1025,13 @@ gdbpy_post_event (PyObject *self, PyObject *args) return NULL; } - Py_INCREF (func); - - /* From here until the end of the function, we have the GIL, so we - can operate on our global data structures without worrying. */ - wakeup = gdbpy_event_list == NULL; - - event = XNEW (struct gdbpy_event); - event->event = func; - event->next = NULL; - *gdbpy_event_list_end = event; - gdbpy_event_list_end = &event->next; - - /* Wake up gdb when needed. */ - if (wakeup) - serial_event_set (gdbpy_serial_event); + gdbpy_ref<> func_ref = gdbpy_ref<>::new_reference (func); + gdbpy_event event (std::move (func_ref)); + run_on_main_thread (event); Py_RETURN_NONE; } -/* Initialize the Python event handler. */ -static int -gdbpy_initialize_events (void) -{ - gdbpy_event_list_end = &gdbpy_event_list; - - gdbpy_serial_event = make_serial_event (); - add_file_handler (serial_event_fd (gdbpy_serial_event), - gdbpy_run_events, NULL); - - return 0; -} - /* This is the extension_language_ops.before_prompt "method". */ @@ -1704,7 +1696,6 @@ do_start_initialization () || gdbpy_initialize_linetable () < 0 || gdbpy_initialize_thread () < 0 || gdbpy_initialize_inferior () < 0 - || gdbpy_initialize_events () < 0 || gdbpy_initialize_eventregistry () < 0 || gdbpy_initialize_py_events () < 0 || gdbpy_initialize_event () < 0 -- 2.30.2