old-cross-binutils/gdb/testsuite/gdb.threads/signal-command-multiple-signals-pending.c

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Always pass signals to the right thread 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.
2014-07-25 15:57:31 +00:00
/* This testcase is part of GDB, the GNU debugger.
Copyright 2014-2015 Free Software Foundation, Inc.
Always pass signals to the right thread 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.
2014-07-25 15:57:31 +00:00
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>
#include <signal.h>
pthread_barrier_t barrier;
sig_atomic_t got_sigusr1;
sig_atomic_t got_sigusr2;
void
handler_sigusr1 (int sig)
{
got_sigusr1 = 1;
}
void
handler_sigusr2 (int sig)
{
got_sigusr2 = 1;
}
void *
thread_function (void *arg)
{
volatile unsigned int count = 1;
pthread_barrier_wait (&barrier);
while (count++ != 0)
{
if (got_sigusr1 && got_sigusr2)
break;
usleep (1);
}
}
void
all_threads_started (void)
{
}
void
all_threads_signalled (void)
{
}
void
end (void)
{
}
int
main (void)
{
pthread_t child_thread[2];
int i;
signal (SIGUSR1, handler_sigusr1);
signal (SIGUSR2, handler_sigusr2);
pthread_barrier_init (&barrier, NULL, 3);
for (i = 0; i < 2; i++)
pthread_create (&child_thread[i], NULL, thread_function, NULL);
pthread_barrier_wait (&barrier);
all_threads_started ();
pthread_kill (child_thread[0], SIGUSR1);
pthread_kill (child_thread[1], SIGUSR2);
all_threads_signalled ();
for (i = 0; i < 2; i++)
pthread_join (child_thread[i], NULL);
end ();
return 0;
}