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Re: [PATCH] Fix 8.2 regression in gdb.python/py-evthreads.exp w/ gdbserver (PR gdb/23379)
- From: Simon Marchi <simon dot marchi at ericsson dot com>
- To: Pedro Alves <palves at redhat dot com>, <gdb-patches at sourceware dot org>
- Date: Fri, 24 Aug 2018 14:52:59 -0400
- Subject: Re: [PATCH] Fix 8.2 regression in gdb.python/py-evthreads.exp w/ gdbserver (PR gdb/23379)
- References: <20180824174616.3306-1-palves@redhat.com>
On 2018-08-24 01:46 PM, Pedro Alves wrote:
> This commit fixes a 8.1->8.2 regression exposed by
> gdb.python/py-evthreads.exp when testing with
> --target_board=native-gdbserver.
>
> gdb.log shows:
>
> src/gdb/thread.c:93: internal-error: thread_info* inferior_thread(): Assertion `tp' failed.
> A problem internal to GDB has been detected,
> further debugging may prove unreliable.
> Quit this debugging session? (y or n) FAIL: gdb.python/py-evthreads.exp: run to breakpoint 1 (GDB internal error)
>
> A backtrace shows (frames #2 and #10 highlighted) that the assertion
> fails when GDB is setting up the connection to the remote target, in
> non-stop mode:
>
> #0 0x0000000000622ff0 in internal_error(char const*, int, char const*, ...) (file=0xc1ad98 "src/gdb/thread.c", line=93, fmt=0xc1ad20 "%s: Assertion `%s' failed.") at src/gdb/common/errors.c:54
> #1 0x000000000089567e in inferior_thread() () at src/gdb/thread.c:93
> = #2 0x00000000004da91d in get_event_thread() () at src/gdb/python/py-threadevent.c:38
> #3 0x00000000004da9b7 in create_thread_event_object(_typeobject*, _object*) (py_type=0x11574c0 <continue_event_object_type>, thread=0x0)
> at src/gdb/python/py-threadevent.c:60
> #4 0x00000000004bf6fe in create_continue_event_object() () at src/gdb/python/py-continueevent.c:27
> #5 0x00000000004bf738 in emit_continue_event(ptid_t) (ptid=...) at src/gdb/python/py-continueevent.c:40
> #6 0x00000000004c7d47 in python_on_resume(ptid_t) (ptid=...) at src/gdb/python/py-inferior.c:108
> #7 0x0000000000485bfb in std::_Function_handler<void (ptid_t), void (*)(ptid_t)>::_M_invoke(std::_Any_data const&, ptid_t&&) (__functor=..., __args#0=...) at /usr/include/c++/7/bits/std_function.h:316
> #8 0x000000000089b416 in std::function<void (ptid_t)>::operator()(ptid_t) const (this=0x12aa600, __args#0=...)
> at /usr/include/c++/7/bits/std_function.h:706
> #9 0x000000000089aa0e in gdb::observers::observable<ptid_t>::notify(ptid_t) const (this=0x118a7a0 <gdb::observers::target_resumed>, args#0=...)
> at src/gdb/common/observable.h:106
> = #10 0x0000000000896fbe in set_running(ptid_t, int) (ptid=..., running=1) at src/gdb/thread.c:880
> #11 0x00000000007f750f in remote_target::remote_add_thread(ptid_t, bool, bool) (this=0x12c5440, ptid=..., running=true, executing=true) at src/gdb/remote.c:2434
> #12 0x00000000007f779d in remote_target::remote_notice_new_inferior(ptid_t, int) (this=0x12c5440, currthread=..., executing=1)
> at src/gdb/remote.c:2515
> #13 0x00000000007f9c44 in remote_target::update_thread_list() (this=0x12c5440) at src/gdb/remote.c:3831
> #14 0x00000000007fb922 in remote_target::start_remote(int, int) (this=0x12c5440, from_tty=0, extended_p=0)
> at src/gdb/remote.c:4655
> #15 0x00000000007fd102 in remote_target::open_1(char const*, int, int) (name=0x1a4f45e "localhost:2346", from_tty=0, extended_p=0)
> at src/gdb/remote.c:5638
> #16 0x00000000007fbec1 in remote_target::open(char const*, int) (name=0x1a4f45e "localhost:2346", from_tty=0)
> at src/gdb/remote.c:4862
>
> So on frame #10, we're marking a newly-discovered thread as running,
> and that causes the Python API to emit a gdb.ContinueEvent.
> gdb.ContinueEvent is a gdb.ThreadEvent, and as such includes the event
> thread as the "inferior_thread" attribute. The problem is that when
> we get to frame #3/#4, we lost all references to the thread that is
> being marked as running. create_continue_event_object assumes that it
> is the current thread, which is not true in this case.
>
> Fix this by passing down the right thread in
> create_continue_event_object. Also remove
> create_thread_event_object's default argument and have the only other
> caller left pass down the right thread explicitly too.
>
> gdb/ChangeLog:
> yyyy-mm-dd Pedro Alves <palves@redhat.com>
>
> PR gdb/23379
> * python/py-continueevent.c: Include "gdbthread.h".
> (create_continue_event_object): Add intro comment. Add 'ptid'
> parameter. Use it to find thread to pass to
> create_thread_event_object.
> (emit_continue_event): Pass PTID down to
> create_continue_event_object.
> * python/py-event.h (py_get_event_thread): Declare.
> (create_thread_event_object): Remove default from 'thread'
> parameter.
> * python/py-stopevent.c (create_stop_event_object): Use
> py_get_event_thread.
> * python/py-threadevent.c (get_event_thread): Rename to ...
> (py_get_event_thread): ... this, and make extern.
> (create_thread_event_object): Assert that THREAD isn't null.
> Don't find the event thread here.
> ---
> gdb/python/py-continueevent.c | 31 ++++++++++++++++++++++++++++---
> gdb/python/py-event.h | 12 +++++++++++-
> gdb/python/py-stopevent.c | 2 +-
> gdb/python/py-threadevent.c | 22 +++++-----------------
> 4 files changed, 45 insertions(+), 22 deletions(-)
>
> diff --git a/gdb/python/py-continueevent.c b/gdb/python/py-continueevent.c
> index e5e922f0155..08d7da3cf2f 100644
> --- a/gdb/python/py-continueevent.c
> +++ b/gdb/python/py-continueevent.c
> @@ -20,11 +20,36 @@
> #include "defs.h"
> #include "py-event.h"
> #include "py-ref.h"
> +#include "gdbthread.h"
> +
> +/* Create a gdb.ContinueEvent event. gdb.ContinueEvent is-a
> + gdb.ThreadEvent, and thread events can either be thread specific or
> + process wide. If gdb is running in non-stop mode then the event is
> + thread specific (in which case the PTID thread is included in the
> + event), otherwise it is process wide (in which case PTID is
> + ignored). In either case a borrowed reference is returned. */
I think the last sentence is wrong. If we are returning a gdbpy_ref, doesn't
mean we are returning an owning reference? From what I understand, a borrowed
reference would be a naked pointer that you don't need to decref.
py_get_event_thread, from which this seems to have been copied from, does indeed
return a borrowed reference.
So it should say "a new reference is returned".
Ref: https://docs.python.org/3.7/c-api/intro.html, ctrl-f "borrow".
> static gdbpy_ref<>
> -create_continue_event_object (void)
> +create_continue_event_object (ptid_t ptid)
> {
> - return create_thread_event_object (&continue_event_object_type);
> + PyObject *py_thr = nullptr;
> +
> + if (non_stop)
> + {
> + thread_info *thr = find_thread_ptid (ptid);
> + if (thr != nullptr)
> + py_thr = (PyObject *) thread_to_thread_object (thr);
> + }
> + else
> + py_thr = Py_None;
> +
> + if (py_thr == nullptr)
> + {
> + PyErr_SetString (PyExc_RuntimeError, _("Could not find event thread"));
> + return nullptr;
> + }
> +
> + return create_thread_event_object (&continue_event_object_type, py_thr);
This and py_get_thread_event look very similar, could we use py_get_thread_event
from here? See the patch at the end of the message.
> }
>
> /* Callback function which notifies observers when a continue event occurs.
> @@ -37,7 +62,7 @@ emit_continue_event (ptid_t ptid)
> if (evregpy_no_listeners_p (gdb_py_events.cont))
> return 0;
>
> - gdbpy_ref<> event (create_continue_event_object ());
> + gdbpy_ref<> event (create_continue_event_object (ptid));
> if (event != NULL)
> return evpy_emit_event (event.get (), gdb_py_events.cont);
> return -1;
> diff --git a/gdb/python/py-event.h b/gdb/python/py-event.h
> index 22bab108ed1..7a9a51ddb1c 100644
> --- a/gdb/python/py-event.h
> +++ b/gdb/python/py-event.h
> @@ -63,8 +63,18 @@ extern int evpy_emit_event (PyObject *event,
> eventregistry_object *registry);
>
> extern gdbpy_ref<> create_event_object (PyTypeObject *py_type);
> +
> +/* thread events can either be thread specific or process wide. If gdb is
> + running in non-stop mode then the event is thread specific, otherwise
> + it is process wide.
> + This function returns the currently stopped thread in non-stop mode and
> + Py_None otherwise. In each case it returns a borrowed reference. */
> +extern PyObject *py_get_event_thread ()
> + CPYCHECKER_RETURNS_BORROWED_REF;
> +
> extern gdbpy_ref<> create_thread_event_object (PyTypeObject *py_type,
> - PyObject *thread = nullptr);
> + PyObject *thread);
> +
> extern int emit_new_objfile_event (struct objfile *objfile);
> extern int emit_clear_objfiles_event (void);
>
> diff --git a/gdb/python/py-stopevent.c b/gdb/python/py-stopevent.c
> index 884e6e3ef8f..33b65f99b80 100644
> --- a/gdb/python/py-stopevent.c
> +++ b/gdb/python/py-stopevent.c
> @@ -23,7 +23,7 @@
> gdbpy_ref<>
> create_stop_event_object (PyTypeObject *py_type)
> {
> - return create_thread_event_object (py_type);
> + return create_thread_event_object (py_type, py_get_event_thread ());
> }
>
> /* Callback observers when a stop event occurs. This function will create a
> diff --git a/gdb/python/py-threadevent.c b/gdb/python/py-threadevent.c
> index d6aa9467b9a..1a115bad801 100644
> --- a/gdb/python/py-threadevent.c
> +++ b/gdb/python/py-threadevent.c
> @@ -20,17 +20,10 @@
> #include "infrun.h"
> #include "gdbthread.h"
>
> -/* thread events can either be thread specific or process wide. If gdb is
> - running in non-stop mode then the event is thread specific, otherwise
> - it is process wide.
> - This function returns the currently stopped thread in non-stop mode and
> - Py_None otherwise. In each case it returns a borrowed reference. */
> +/* See py-event.h. */
>
> -static PyObject *get_event_thread (void)
> - CPYCHECKER_RETURNS_BORROWED_REF;
> -
> -static PyObject *
> -get_event_thread (void)
> +PyObject *
> +py_get_event_thread ()
> {
> PyObject *thread;
>
> @@ -51,17 +44,12 @@ get_event_thread (void)
> gdbpy_ref<>
> create_thread_event_object (PyTypeObject *py_type, PyObject *thread)
> {
> + gdb_assert (thread != NULL);
> +
> gdbpy_ref<> thread_event_obj (create_event_object (py_type));
You mentioned at some point that you preferred
gdbpy_ref<> thread_event_obj = create_event_object (py_type);
over
gdbpy_ref<> thread_event_obj (create_event_object (py_type));
(which I agree with).
> if (thread_event_obj == NULL)
> return NULL;
>
> - if (thread == NULL)
> - {
> - thread = get_event_thread ();
> - if (!thread)
> - return NULL;
> - }
> -
> if (evpy_add_attribute (thread_event_obj.get (),
> "inferior_thread",
> thread) < 0)
>
Proposed changes:
>From 6b789cb151b5160fca3e3c90d47fb921e3d7697e Mon Sep 17 00:00:00 2001
From: Simon Marchi <simon.marchi@ericsson.com>
Date: Fri, 24 Aug 2018 14:26:23 -0400
Subject: [PATCH] Use py_get_event_thread in create_continue_event_object
---
gdb/python/py-continueevent.c | 18 +++---------------
gdb/python/py-event.h | 2 +-
gdb/python/py-stopevent.c | 3 ++-
gdb/python/py-threadevent.c | 16 ++++++++++------
4 files changed, 16 insertions(+), 23 deletions(-)
diff --git a/gdb/python/py-continueevent.c b/gdb/python/py-continueevent.c
index 08d7da3..c011b71 100644
--- a/gdb/python/py-continueevent.c
+++ b/gdb/python/py-continueevent.c
@@ -32,22 +32,10 @@
static gdbpy_ref<>
create_continue_event_object (ptid_t ptid)
{
- PyObject *py_thr = nullptr;
-
- if (non_stop)
- {
- thread_info *thr = find_thread_ptid (ptid);
- if (thr != nullptr)
- py_thr = (PyObject *) thread_to_thread_object (thr);
- }
- else
- py_thr = Py_None;
+ PyObject *py_thr = py_get_event_thread (ptid);
if (py_thr == nullptr)
- {
- PyErr_SetString (PyExc_RuntimeError, _("Could not find event thread"));
- return nullptr;
- }
+ return nullptr;
return create_thread_event_object (&continue_event_object_type, py_thr);
}
@@ -62,7 +50,7 @@ emit_continue_event (ptid_t ptid)
if (evregpy_no_listeners_p (gdb_py_events.cont))
return 0;
- gdbpy_ref<> event (create_continue_event_object (ptid));
+ gdbpy_ref<> event = create_continue_event_object (ptid);
if (event != NULL)
return evpy_emit_event (event.get (), gdb_py_events.cont);
return -1;
diff --git a/gdb/python/py-event.h b/gdb/python/py-event.h
index 7a9a51d..56003e8 100644
--- a/gdb/python/py-event.h
+++ b/gdb/python/py-event.h
@@ -69,7 +69,7 @@ extern gdbpy_ref<> create_event_object (PyTypeObject *py_type);
it is process wide.
This function returns the currently stopped thread in non-stop mode and
Py_None otherwise. In each case it returns a borrowed reference. */
-extern PyObject *py_get_event_thread ()
+extern PyObject *py_get_event_thread (ptid_t ptid)
CPYCHECKER_RETURNS_BORROWED_REF;
extern gdbpy_ref<> create_thread_event_object (PyTypeObject *py_type,
diff --git a/gdb/python/py-stopevent.c b/gdb/python/py-stopevent.c
index 33b65f9..f6bd207 100644
--- a/gdb/python/py-stopevent.c
+++ b/gdb/python/py-stopevent.c
@@ -23,7 +23,8 @@
gdbpy_ref<>
create_stop_event_object (PyTypeObject *py_type)
{
- return create_thread_event_object (py_type, py_get_event_thread ());
+ return create_thread_event_object (py_type,
+ py_get_event_thread (inferior_ptid));
}
/* Callback observers when a stop event occurs. This function will create a
diff --git a/gdb/python/py-threadevent.c b/gdb/python/py-threadevent.c
index 1a115ba..1bc2fb0 100644
--- a/gdb/python/py-threadevent.c
+++ b/gdb/python/py-threadevent.c
@@ -23,22 +23,26 @@
/* See py-event.h. */
PyObject *
-py_get_event_thread ()
+py_get_event_thread (ptid_t ptid)
{
- PyObject *thread;
+ PyObject *pythread;
if (non_stop)
- thread = (PyObject *) thread_to_thread_object (inferior_thread ());
+ {
+ thread_info *thread = find_thread_ptid (ptid);
+ if (thread != nullptr)
+ pythread = (PyObject *) thread_to_thread_object (thread);
+ }
else
- thread = Py_None;
+ pythread = Py_None;
- if (!thread)
+ if (!pythread)
{
PyErr_SetString (PyExc_RuntimeError, "Could not find event thread");
return NULL;
}
- return thread;
+ return pythread;
}
gdbpy_ref<>
--
2.7.4