705096250d
Currently, GDB can pass a signal to the wrong thread in several
different but related scenarios.
E.g., if thread 1 stops for signal SIGFOO, the user switches to thread
2, and then issues "continue", SIGFOO is actually delivered to thread
2, not thread 1. This obviously messes up programs that use
pthread_kill to send signals to specific threads.
This has been a known issue for a long while. Back in 2008 when I
made stop_signal be per-thread (2020b7ab), I kept the behavior -- see
code in 'proceed' being removed -- wanting to come back to it later.
The time has finally come now.
The patch fixes this -- on resumption, intercepted signals are always
delivered to the thread that had intercepted them.
Another example: if thread 1 stops for a breakpoint, the user switches
to thread 2, and then issues "signal SIGFOO", SIGFOO is actually
delivered to thread 1, not thread 2, because 'proceed' first switches
to thread 1 to step over its breakpoint... If the user deletes the
breakpoint before issuing "signal FOO", then the signal is delivered
to thread 2 (the current thread).
"signal SIGFOO" can be used for two things: inject a signal in the
program while the program/thread had stopped for none, bypassing
"handle nopass"; or changing/suppressing a signal the program had
stopped for. These scenarios are really two faces of the same coin,
and GDB can't really guess what the user is trying to do. GDB might
have intercepted signals in more than one thread even (see the new
signal-command-multiple-signals-pending.exp test). At least in the
inject case, it's obviously clear to me that the user means to deliver
the signal to the currently selected thread, so best is to make the
command's behavior consistent and easy to explain.
Then, if the user is trying to suppress/change a signal the program
had stopped for instead of injecting a new signal, but, the user had
changed threads meanwhile, then she will be surprised that with:
(gdb) continue
Thread 1 stopped for signal SIGFOO.
(gdb) thread 2
(gdb) signal SIGBAR
... GDB actually delivers SIGFOO to thread 1, and SIGBAR to thread 2
(with scheduler-locking off, which is the default, because then
"signal" or any other resumption command resumes all threads).
So the patch makes GDB detect that, and ask for confirmation:
(gdb) thread 1
[Switching to thread 1 (Thread 10979)]
(gdb) signal SIGUSR2
Note:
Thread 3 previously stopped with signal SIGUSR2, User defined signal 2.
Thread 2 previously stopped with signal SIGUSR1, User defined signal 1.
Continuing thread 1 (the current thread) with specified signal will
still deliver the signals noted above to their respective threads.
Continue anyway? (y or n)
All these scenarios are covered by the new tests.
Tested on x86_64 Fedora 20, native and gdbserver.
gdb/
2014-07-25 Pedro Alves <palves@redhat.com>
* NEWS: Mention signal passing and "signal" command changes.
* gdbthread.h (struct thread_suspend_state) <stop_signal>: Extend
comment.
* breakpoint.c (until_break_command): Adjust clear_proceed_status
call.
* infcall.c (run_inferior_call): Adjust clear_proceed_status call.
* infcmd.c (proceed_thread_callback, continue_1, step_once)
(jump_command): Adjust clear_proceed_status call.
(signal_command): Warn if other thread that are resumed have
signals that will be delivered. Adjust clear_proceed_status call.
(until_next_command, finish_command)
(proceed_after_attach_callback, attach_command_post_wait)
(attach_command): Adjust clear_proceed_status call.
* infrun.c (proceed_after_vfork_done): Likewise.
(proceed_after_attach_callback): Adjust comment.
(clear_proceed_status_thread): Clear stop_signal if not in pass
state.
(clear_proceed_status_callback): Delete.
(clear_proceed_status): New 'step' parameter. Only clear the
proceed status of threads the command being prepared is about to
resume.
(proceed): If passed in an explicit signal, override stop_signal
with it. Don't pass the last stop signal to the thread we're
resuming.
(init_wait_for_inferior): Adjust clear_proceed_status call.
(switch_back_to_stepped_thread): Clear the signal if it should not
be passed.
* infrun.h (clear_proceed_status): New 'step' parameter.
(user_visible_resume_ptid): Add comment.
* linux-nat.c (linux_nat_resume_callback): Don't check whether the
signal is in pass state.
* remote.c (append_pending_thread_resumptions): Likewise.
* mi/mi-main.c (proceed_thread): Adjust clear_proceed_status call.
gdb/doc/
2014-07-25 Pedro Alves <palves@redhat.com>
Eli Zaretskii <eliz@gnu.org>
* gdb.texinfo (Signaling) <signal command>: Explain what happens
with multi-threaded programs.
gdb/testsuite/
2014-07-25 Pedro Alves <palves@redhat.com>
* gdb.threads/signal-command-handle-nopass.c: New file.
* gdb.threads/signal-command-handle-nopass.exp: New file.
* gdb.threads/signal-command-multiple-signals-pending.c: New file.
* gdb.threads/signal-command-multiple-signals-pending.exp: New file.
* gdb.threads/signal-delivered-right-thread.c: New file.
* gdb.threads/signal-delivered-right-thread.exp: New file.
192 lines
6.7 KiB
C
192 lines
6.7 KiB
C
/* Copyright (C) 1986-2014 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef INFRUN_H
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#define INFRUN_H 1
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#include "ptid.h"
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#include "symtab.h"
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struct target_waitstatus;
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struct frame_info;
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struct address_space;
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/* True if we are debugging run control. */
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extern unsigned int debug_infrun;
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/* True if we are debugging displaced stepping. */
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extern int debug_displaced;
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/* Nonzero if we want to give control to the user when we're notified
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of shared library events by the dynamic linker. */
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extern int stop_on_solib_events;
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/* Are we simulating synchronous execution? This is used in async gdb
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to implement the 'run', 'continue' etc commands, which will not
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redisplay the prompt until the execution is actually over. */
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extern int sync_execution;
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/* True if execution commands resume all threads of all processes by
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default; otherwise, resume only threads of the current inferior
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process. */
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extern int sched_multi;
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/* When set, stop the 'step' command if we enter a function which has
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no line number information. The normal behavior is that we step
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over such function. */
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extern int step_stop_if_no_debug;
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/* If set, the inferior should be controlled in non-stop mode. In
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this mode, each thread is controlled independently. Execution
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commands apply only to the selected thread by default, and stop
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events stop only the thread that had the event -- the other threads
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are kept running freely. */
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extern int non_stop;
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/* When set (default), the target should attempt to disable the
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operating system's address space randomization feature when
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starting an inferior. */
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extern int disable_randomization;
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/* Reverse execution. */
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enum exec_direction_kind
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{
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EXEC_FORWARD,
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EXEC_REVERSE
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};
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/* The current execution direction. This should only be set to enum
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exec_direction_kind values. It is only an int to make it
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compatible with make_cleanup_restore_integer. */
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extern int execution_direction;
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/* Save register contents here when executing a "finish" command or
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are about to pop a stack dummy frame, if-and-only-if
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proceed_to_finish is set. Thus this contains the return value from
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the called function (assuming values are returned in a
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register). */
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extern struct regcache *stop_registers;
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extern void start_remote (int from_tty);
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/* Clear out all variables saying what to do when inferior is
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continued or stepped. First do this, then set the ones you want,
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then call `proceed'. STEP indicates whether we're preparing for a
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step/stepi command. */
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extern void clear_proceed_status (int step);
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extern void proceed (CORE_ADDR, enum gdb_signal, int);
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/* The `resume' routine should only be called in special circumstances.
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Normally, use `proceed', which handles a lot of bookkeeping. */
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extern void resume (int, enum gdb_signal);
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/* Return a ptid representing the set of threads that we will proceed,
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in the perspective of the user/frontend. */
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extern ptid_t user_visible_resume_ptid (int step);
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extern void wait_for_inferior (void);
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extern void normal_stop (void);
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extern void get_last_target_status (ptid_t *ptid,
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struct target_waitstatus *status);
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extern void prepare_for_detach (void);
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extern void fetch_inferior_event (void *);
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extern void init_wait_for_inferior (void);
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extern void insert_step_resume_breakpoint_at_sal (struct gdbarch *,
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struct symtab_and_line ,
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struct frame_id);
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extern void follow_inferior_reset_breakpoints (void);
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/* Returns true if we're trying to step past the instruction at
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ADDRESS in ASPACE. */
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extern int stepping_past_instruction_at (struct address_space *aspace,
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CORE_ADDR address);
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extern void set_step_info (struct frame_info *frame,
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struct symtab_and_line sal);
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/* Several print_*_reason helper functions to print why the inferior
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has stopped to the passed in UIOUT. */
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/* Signal received, print why the inferior has stopped. */
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extern void print_signal_received_reason (struct ui_out *uiout,
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enum gdb_signal siggnal);
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/* Print why the inferior has stopped. We are done with a
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step/next/si/ni command, print why the inferior has stopped. */
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extern void print_end_stepping_range_reason (struct ui_out *uiout);
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/* The inferior was terminated by a signal, print why it stopped. */
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extern void print_signal_exited_reason (struct ui_out *uiout,
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enum gdb_signal siggnal);
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/* The inferior program is finished, print why it stopped. */
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extern void print_exited_reason (struct ui_out *uiout, int exitstatus);
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/* Reverse execution: target ran out of history info, print why the
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inferior has stopped. */
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extern void print_no_history_reason (struct ui_out *uiout);
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extern void print_stop_event (struct target_waitstatus *ws);
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extern int signal_stop_state (int);
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extern int signal_print_state (int);
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extern int signal_pass_state (int);
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extern int signal_stop_update (int, int);
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extern int signal_print_update (int, int);
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extern int signal_pass_update (int, int);
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extern void update_signals_program_target (void);
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/* Clear the convenience variables associated with the exit of the
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inferior. Currently, those variables are $_exitcode and
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$_exitsignal. */
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extern void clear_exit_convenience_vars (void);
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/* Dump LEN bytes at BUF in hex to FILE, followed by a newline. */
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extern void displaced_step_dump_bytes (struct ui_file *file,
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const gdb_byte *buf, size_t len);
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extern struct displaced_step_closure *get_displaced_step_closure_by_addr
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(CORE_ADDR addr);
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extern void update_observer_mode (void);
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extern void signal_catch_update (const unsigned int *);
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/* In some circumstances we allow a command to specify a numeric
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signal. The idea is to keep these circumstances limited so that
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users (and scripts) develop portable habits. For comparison,
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POSIX.2 `kill' requires that 1,2,3,6,9,14, and 15 work (and using a
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numeric signal at all is obsolescent. We are slightly more lenient
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and allow 1-15 which should match host signal numbers on most
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systems. Use of symbolic signal names is strongly encouraged. */
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enum gdb_signal gdb_signal_from_command (int num);
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#endif /* INFRUN_H */
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