We have places where we call a blocking gdb_select expecting that a
Ctrl-C will unblock it. However, if the Ctrl-C is pressed just before
gdb_select, the SIGINT handler runs before gdb_select, and thus
gdb_select won't return.
For example gdb_readline_no_editing:
QUIT;
/* Wait until at least one byte of data is available. Control-C
can interrupt gdb_select, but not fgetc. */
FD_ZERO (&readfds);
FD_SET (fd, &readfds);
if (gdb_select (fd + 1, &readfds, NULL, NULL, NULL) == -1)
and stdio_file_read:
/* For the benefit of Windows, call gdb_select before reading from
the file. Wait until at least one byte of data is available.
Control-C can interrupt gdb_select, but not read. */
{
fd_set readfds;
FD_ZERO (&readfds);
FD_SET (stdio->fd, &readfds);
if (gdb_select (stdio->fd + 1, &readfds, NULL, NULL, NULL) == -1)
return -1;
}
return read (stdio->fd, buf, length_buf);
This is a race classically fixed with either the self-pipe trick, or
by blocking SIGINT and then using pselect instead of select.
Blocking SIGINT most of the time would mean that check_quit_flag (and
thus QUIT) would need to do a syscall every time it is called, which
sounds best avoided, since QUIT is called in many loops. Thus we take
the self-pipe trick route (wrapped in a serial event).
Instead of having all places that need this manually add an extra file
descriptor to the set of gdb_select's watched file descriptors, we
introduce a wrapper, interruptible_select, that does that.
The Windows version of gdb_select actually does not suffer from this,
because mingw-hdep.c:gdb_call_async_signal_handler sets a Windows
event that gdb_select always waits on. So this patch can be seen as
generalization of that technique. We can't remove that extra event
from mingw-hdep.c until we get rid of immediate_quit though.
gdb/ChangeLog:
2016-04-12 Pedro Alves <palves@redhat.com>
* defs.h: Extend QUIT-related comments to mention
interruptible_select.
(quit_serial_event_set, quit_serial_event_clear): Declare.
* event-top.c: Include "ser-event.h" and "gdb_select.h".
(quit_serial_event): New global.
(async_init_signals): Make quit_serial_event.
(quit_serial_event_set, quit_serial_event_clear)
(quit_serial_event_fd, interruptible_select): New functions.
* extension.c (set_quit_flag): Set the quit serial event.
(check_quit_flag): Clear the quit serial event.
* gdb_select.h (interruptible_select): New declaration.
* guile/scm-ports.c (ioscm_input_waiting): Use
interruptible_select instead of gdb_select.
* top.c (gdb_readline_no_editing): Likewise.
* ui-file.c (stdio_file_read): Likewise.
I see a timeout in gdb.base/random-signal.exp,
Continuing.^M
PASS: gdb.base/random-signal.exp: continue
^CPython Exception <type 'exceptions.KeyboardInterrupt'> <type
exceptions.KeyboardInterrupt'>: ^M
FAIL: gdb.base/random-signal.exp: stop with control-c (timeout)
it can be reproduced by running random-signal.exp with native-gdbserver
in a loop, like this, and the fail will be shown in about 20 runs,
$ (set -e; while true; do make check RUNTESTFLAGS="--target_board=native-gdbserver random-signal.exp"; done)
In the test, the program is being single-stepped for software watchpoint,
and in each internal stop, python unwinder sniffer is used,
#0 pyuw_sniffer (self=<optimised out>, this_frame=<optimised out>, cache_ptr=0xd554f8) at /home/yao/SourceCode/gnu/gdb/git/gdb/python/py-unwind.c:608
#1 0x00000000006a10ae in frame_unwind_try_unwinder (this_frame=this_frame@entry=0xd554e0, this_cache=this_cache@entry=0xd554f8, unwinder=0xecd540)
at /home/yao/SourceCode/gnu/gdb/git/gdb/frame-unwind.c:107
#2 0x00000000006a143f in frame_unwind_find_by_frame (this_frame=this_frame@entry=0xd554e0, this_cache=this_cache@entry=0xd554f8)
at /home/yao/SourceCode/gnu/gdb/git/gdb/frame-unwind.c:163
#3 0x000000000069dc6b in compute_frame_id (fi=0xd554e0) at /home/yao/SourceCode/gnu/gdb/git/gdb/frame.c:454
#4 get_prev_frame_if_no_cycle (this_frame=this_frame@entry=0xd55410) at /home/yao/SourceCode/gnu/gdb/git/gdb/frame.c:1781
#5 0x000000000069fdb9 in get_prev_frame_always_1 (this_frame=0xd55410) at /home/yao/SourceCode/gnu/gdb/git/gdb/frame.c:1955
#6 get_prev_frame_always (this_frame=this_frame@entry=0xd55410) at /home/yao/SourceCode/gnu/gdb/git/gdb/frame.c:1971
#7 0x00000000006a04b1 in get_prev_frame (this_frame=this_frame@entry=0xd55410) at /home/yao/SourceCode/gnu/gdb/git/gdb/frame.c:2213
when GDB goes to python extension, or other language extension, the
SIGINT handler is changed, and is restored when GDB leaves extension
language. GDB only stays in extension language for a very short period
in this case, but if ctrl-c is pressed at that moment, python extension
will handle the SIGINT, and exceptions.KeyboardInterrupt is shown.
Language extension is used in GDB side rather than inferior side,
so GDB should only change SIGINT handler for extension language when
the terminal is ours (not inferior's). This is what this patch does.
With this patch applied, I run random-signal.exp in a loop for 18
hours, and no fail is shown.
gdb:
2016-01-08 Yao Qi <yao.qi@linaro.org>
* extension.c: Include target.h.
(set_active_ext_lang): Only call install_gdb_sigint_handler,
check_quit_flag, and set_quit_flag if target_terminal_is_ours
returns false.
(restore_active_ext_lang): Likewise.
* target.c (target_terminal_is_ours): New function.
* target.h (target_terminal_is_ours): Declare.
This fixes 14 build errors like these in C++ mode:
src/gdb/extension.c: In function ‘void install_sigint_handler(const signal_handler*)’:
src/gdb/extension.c:698:41: error: invalid conversion from ‘void (*)()’ to ‘__sighandler_t {aka void (*)(int)}’ [-fpermissive]
signal (SIGINT, handler_state->handler);
^
In file included from build-gnulib/import/signal.h:52:0,
from ../../src/gdb/extension.c:24:
/usr/include/signal.h:102:23: error: initializing argument 2 of ‘void (* signal(int, __sighandler_t))(int)’ [-fpermissive]
extern __sighandler_t signal (int __sig, __sighandler_t __handler)
^
Instead of this everywhere:
- RETSIGTYPE (*handle_sigint_for_compare) () = handle_sigint;
+ RETSIGTYPE (*handle_sigint_for_compare) (int) = handle_sigint;
Use sighandler_t (a GNU extension). That's OK to use unconditionaly
because gnulib's signal.h replacement makes sure that it is available.
gdb/ChangeLog:
2015-08-27 Pedro Alves <palves@redhat.com>
* cp-support.c (gdb_demangle): Use sighandler_t. Remove cast.
* extension-priv.h: Include signal.h.
(struct signal_handler) <handler>: Change type to sighandler_t.
* extension.c (install_gdb_sigint_handler): Use sighandler_t.
* inflow.c (sigint_ours, sigquit_ours): Change type to
sighandler_t.
(child_terminal_inferior): Remove casts.
(child_terminal_ours_1, new_tty): Use sighandler_t. Remove casts.
(osig): Change type to sighandler_t.
* nto-procfs.c (ofunc): Change type to sighandler_t.
(procfs_wait): Remove casts.
* remote-m32r-sdi.c (m32r_wait, m32r_load): Use sighandler_t.
* remote-sim.c (gdbsim_wait): Use sighandler_t.
* utils.c (wait_to_die_with_timeout): Use sighandler_t.
* defs.h (enum lval_type): New enumerator "lval_xcallable".
* extension-priv.h (struct extension_language_ops): Add the
xmethod interface.
* extension.c (new_xmethod_worker, clone_xmethod_worker,
get_matching_xmethod_workers, get_xmethod_argtypes,
invoke_xmethod, free_xmethod_worker,
free_xmethod_worker_vec): New functions.
* extension.h: #include "common/vec.h".
New function declarations.
(struct xmethod_worker): New struct.
(VEC (xmethod_worker_ptr)): New vector type.
(xmethod_worker_ptr): New typedef.
(xmethod_worker_vec): Likewise.
* gdbtypes.c (gdbtypes_post_init): Initialize "xmethod" field of
builtin_type.
* gdbtypes.h (enum type_code): New enumerator TYPE_CODE_XMETHOD.
(struct builtin_type): New field "xmethod".
* valarith.c (value_ptradd): Assert that the value argument is not
lval_xcallable.
* valops.c (value_must_coerce_to_target): Return 0 for
lval_xcallable values.
* value.c (struct value): New field XM_WORKER in the field
LOCATION.
(value_address, value_raw_address): Return 0 for lval_xcallable
values.
(set_value_address): Assert that the value is not an
lval_xcallable.
(value_free): Free the associated xmethod worker when freeing
lval_xcallable values.
(set_value_component_location): Assert that the WHOLE value is not
lval_xcallable.
(value_of_xmethod, call_xmethod): New functions.
* value.h: Declare "struct xmethod_worker".
Declare new functions value_of_xmethod, call_xmethod.
* configure.ac (libpython checking): Remove all but python.o from
CONFIG_OBS. Remove all but python.c from CONFIG_SRCS.
* configure: Regenerate.
* Makefile.in (SFILES): Add extension.c.
(HFILES_NO_SRCDIR): Add extension.h, extension-priv.h
(COMMON_OBS): Add extension.o.
* extension.h: New file.
* extension-priv.h: New file.
* extension.c: New file.
* python/python-internal.h: #include "extension.h".
(gdbpy_auto_load_enabled): Declare.
(gdbpy_apply_val_pretty_printer): Declare.
(gdbpy_apply_frame_filter): Declare.
(gdbpy_preserve_values): Declare.
(gdbpy_breakpoint_cond_says_stop): Declare.
(gdbpy_breakpoint_has_cond): Declare.
(void source_python_script_for_objfile): Delete.
* python/python.c: #include "extension-priv.h".
Delete inclusion of "observer.h".
(extension_language_python): Moved here and renamed from
script_language_python in py-auto-load.c.
Redefined to be of type extension_language_defn.
(python_extension_script_ops): New global.
(python_extension_ops): New global.
(struct python_env): New member previous_active.
(restore_python_env): Call restore_active_ext_lang.
(ensure_python_env): Call set_active_ext_lang.
(gdbpy_clear_quit_flag): Renamed from clear_quit_flag, made static.
New arg extlang.
(gdbpy_set_quit_flag): Renamed from set_quit_flag, made static.
New arg extlang.
(gdbpy_check_quit_flag): Renamed from check_quit_flag, made static.
New arg extlang.
(gdbpy_eval_from_control_command): Renamed from
eval_python_from_control_command, made static. New arg extlang.
(gdbpy_source_script) Renamed from source_python_script, made static.
New arg extlang.
(gdbpy_before_prompt_hook): Renamed from before_prompt_hook. Change
result to int. New arg extlang.
(gdbpy_source_objfile_script): Renamed from
source_python_script_for_objfile, made static. New arg extlang.
(gdbpy_start_type_printers): Renamed from start_type_printers, made
static. New args extlang, extlang_printers. Change result type to
"void".
(gdbpy_apply_type_printers): Renamed from apply_type_printers, made
static. New arg extlang. Rename arg printers to extlang_printers
and change type to ext_lang_type_printers *.
(gdbpy_free_type_printers): Renamed from free_type_printers, made
static. Replace argument arg with extlang, extlang_printers.
(!HAVE_PYTHON, eval_python_from_control_command): Delete.
(!HAVE_PYTHON, source_python_script): Delete.
(!HAVE_PYTHON, gdbpy_should_stop): Delete.
(!HAVE_PYTHON, gdbpy_breakpoint_has_py_cond): Delete.
(!HAVE_PYTHON, start_type_printers): Delete.
(!HAVE_PYTHON, apply_type_printers): Delete.
(!HAVE_PYTHON, free_type_printers): Delete.
(_initialize_python): Delete call to observer_attach_before_prompt.
(finalize_python): Set/restore active extension language.
(gdbpy_finish_initialization) Renamed from
finish_python_initialization, made static. New arg extlang.
(gdbpy_initialized): New function.
* python/python.h: #include "extension.h". Delete #include
"value.h", "mi/mi-cmds.h".
(extension_language_python): Declare.
(GDBPY_AUTO_FILE_NAME): Delete.
(enum py_bt_status): Moved to extension.h and renamed to
ext_lang_bt_status.
(enum frame_filter_flags): Moved to extension.h.
(enum py_frame_args): Moved to extension.h and renamed to
ext_lang_frame_args.
(finish_python_initialization): Delete.
(eval_python_from_control_command): Delete.
(source_python_script): Delete.
(apply_val_pretty_printer): Delete.
(apply_frame_filter): Delete.
(preserve_python_values): Delete.
(gdbpy_script_language_defn): Delete.
(gdbpy_should_stop, gdbpy_breakpoint_has_py_cond): Delete.
(start_type_printers, apply_type_printers, free_type_printers): Delete.
* auto-load.c: #include "extension.h".
(GDB_AUTO_FILE_NAME): Delete.
(auto_load_gdb_scripts_enabled): Make public. New arg extlang.
(script_language_gdb): Delete, moved to extension.c and renamed to
extension_language_gdb.
(source_gdb_script_for_objfile): Delete.
(auto_load_pspace_info): New member unsupported_script_warning_printed.
(loaded_script): Change type of language member to
struct extension_language_defn *.
(init_loaded_scripts_info): Initialize
unsupported_script_warning_printed.
(maybe_add_script): Make static. Change type of language arg to
struct extension_language_defn *.
(clear_section_scripts): Reset unsupported_script_warning_printed.
(auto_load_objfile_script_1): Rewrite to use extension language API.
(auto_load_objfile_script): Make public. Remove support-compiled-in
and auto-load-enabled checks, moved to auto_load_scripts_for_objfile.
(source_section_scripts): Rewrite to use extension language API.
(load_auto_scripts_for_objfile): Rewrite to use
auto_load_scripts_for_objfile.
(collect_matching_scripts_data): Change type of language member to
struct extension_language_defn *.
(auto_load_info_scripts): Change type of language arg to
struct extension_language_defn *.
(unsupported_script_warning_print): New function.
(script_not_found_warning_print): Make static.
(_initialize_auto_load): Rewrite construction of scripts-directory
help.
* auto-load.h (struct objfile): Add forward decl.
(struct script_language): Delete.
(struct auto_load_pspace_info): Add forward decl.
(struct extension_language_defn): Add forward decl.
(maybe_add_script): Delete.
(auto_load_objfile_script): Declare.
(script_not_found_warning_print): Delete.
(auto_load_info_scripts): Update prototype.
(auto_load_gdb_scripts_enabled): Declare.
* python/py-auto-load.c (gdbpy_auto_load_enabled): Renamed from
auto_load_python_scripts_enabled and made public.
(script_language_python): Delete, moved to python.c.
(gdbpy_script_language_defn): Delete.
(info_auto_load_python_scripts): Update to use
extension_language_python.
* breakpoint.c (condition_command): Replace call to
gdbpy_breakpoint_has_py_cond with call to get_breakpoint_cond_ext_lang.
(bpstat_check_breakpoint_conditions): Replace call to gdbpy_should_stop
with call to breakpoint_ext_lang_cond_says_stop.
* python/py-breakpoint.c (gdbpy_breakpoint_cond_says_stop): Renamed
from gdbpy_should_stop. Change result type to enum scr_bp_stop.
New arg slang. Return SCR_BP_STOP_UNSET if py_bp_object is NULL.
(gdbpy_breakpoint_has_cond): Renamed from gdbpy_breakpoint_has_py_cond.
New arg slang.
(local_setattro): Print name of extension language with existing
stop condition.
* valprint.c (val_print, value_print): Update to call
apply_ext_lang_val_pretty_printer.
* cp-valprint.c (cp_print_value): Update call to
apply_ext_lang_val_pretty_printer.
* python/py-prettyprint.c: Remove #ifdef HAVE_PYTHON.
(gdbpy_apply_val_pretty_printer): Renamed from
apply_val_pretty_printer. New arg extlang.
(!HAVE_PYTHON, apply_val_pretty_printer): Delete.
* cli/cli-cmds.c (source_script_from_stream): Rewrite to use
extension language API.
* cli/cli-script.c (execute_control_command): Update to call
eval_ext_lang_from_control_command.
* mi/mi-cmd-stack.c (mi_cmd_stack_list_frames): Update to use
enum ext_lang_bt_status values. Update call to
apply_ext_lang_frame_filter.
(mi_cmd_stack_list_locals): Ditto.
(mi_cmd_stack_list_args): Ditto.
(mi_cmd_stack_list_variables): Ditto.
* mi/mi-main.c: Delete #include "python/python-internal.h".
Add #include "extension.h".
(mi_cmd_list_features): Replace reference to python internal variable
gdb_python_initialized with call to ext_lang_initialized_p.
* stack.c (backtrace_command_1): Update to use enum ext_lang_bt_status.
Update to use enum ext_lang_frame_args. Update to call
apply_ext_lang_frame_filter.
* python/py-framefilter.c (extract_sym): Update to use enum
ext_lang_bt_status.
(extract_value, py_print_type, py_print_value): Ditto.
(py_print_single_arg, enumerate_args, enumerate_locals): Ditto.
(py_mi_print_variables, py_print_locals, py_print_args): Ditto.
(py_print_frame): Ditto.
(gdbpy_apply_frame_filter): Renamed from apply_frame_filter.
New arg extlang. Update to use enum ext_lang_bt_status.
* top.c (gdb_init): Delete #ifdef HAVE_PYTHON call to
finish_python_initialization. Replace with call to
finish_ext_lang_initialization.
* typeprint.c (do_free_global_table): Update to call
free_ext_lang_type_printers.
(create_global_typedef_table): Update to call
start_ext_lang_type_printers.
(find_global_typedef): Update to call apply_ext_lang_type_printers.
* typeprint.h (struct ext_lang_type_printers): Add forward decl.
(type_print_options): Change type of global_printers from "void *"
to "struct ext_lang_type_printers *".
* value.c (preserve_values): Update to call preserve_ext_lang_values.
* python/py-value.c: Remove #ifdef HAVE_PYTHON.
(gdbpy_preserve_values): Renamed from preserve_python_values.
New arg extlang.
(!HAVE_PYTHON, preserve_python_values): Delete.
* utils.c (quit_flag): Delete, moved to extension.c.
(clear_quit_flag, set_quit_flag, check_quit_flag): Delete, moved to
extension.c.
* eval.c: Delete #include "python/python.h".
* main.c: Delete #include "python/python.h".
* defs.h: Update comment.
testsuite/
* gdb.python/py-breakpoint.exp (test_bkpt_eval_funcs): Update expected
output.
* gdb.gdb/python-interrupts.exp: New file.
Trevor Saunders
Pedro Alves
Yao Qi
Joel Brobecker
Doug Evans
Doug Evans
Siva Chandra