old-cross-binutils/gdb/testsuite/gdb.threads/reconnect-signal.c

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[remote/gdbserver] Don't lose signals when reconnecting. Currently, when GDB connects in all-stop mode, GDBserver always responds to the status packet with a GDB_SIGNAL_TRAP, even if the program is actually stopped for some other signal. (gdb) tar rem ... ... (gdb) c Program received signal SIGUSR1, User defined signal 1. (gdb) disconnect (gdb) tar rem ... (gdb) c (Or a GDB crash instead of an explicit disconnect.) This results in the program losing that signal on that last continue, because gdb will tell the target to resume with no signal (to suppress the GDB_SIGNAL_TRAP, due to 'handle SISGTRAP nopass'), and that will actually suppress the real signal the program had stopped for (SIGUSR1). To fix that, I think we should make GDBserver report the real signal the thread had stopped for in response to the status packet: @item ? @cindex @samp{?} packet Indicate the reason the target halted. The reply is the same as for step and continue. But, that raises the question -- which thread are we reporting the status for? Due to how the RSP in all-stop works, we can only report one status. The status packet's response is a stop reply packet, so it includes the thread identifier, so it's not a problem packet-wise. However, GDBserver is currently always reporting the status for first thread in the thread list, even though that may well not be the thread that got the signal that caused the program to stop. So the next logical step would be to report the status for the last_ptid/last_status thread (the last event reported to gdb), if it's still around; and if not, fallback to some other thread. There's an issue on the GDB side with that, though... GDB currently always adds the thread reported in response to the status query as the first thread in its list. That means that if we start with e.g., (gdb) info threads 3 Thread 1003 ... * 2 Thread 1002 ... 1 Thread 1001 ... And reconnect: (gdb) disconnect (gdb) tar rem ... We end up with: (gdb) info threads 3 Thread 1003 ... 2 Thread 1001 ... * 1 Thread 1002 ... Not a real big issue, but it's reasonably fixable, by having GDB fetch/sync the thread list before fetching the status/'?', and then using the status to select the right thread as current on the GDB side. Holes in the thread numbers are squashed before/after reconnection (e.g., 2,3,5 becomes 1,2,3), but the order is preserved, which I think is both good, and good enough. However (yes, there's more...), the previous GDB that was connected might have had gdbserver running in non-stop mode, or could have left gdbserver doing disconnected tracing (which also forces non-stop), and if the new gdb/connection is in all-stop mode, we can end up with more than one thread with a signal to report back to gdb. As we can only report one thread/status (in the all-stop RSP variant; the non-stop variant doesn't have this issue), we get to do what we do at every other place we have this situation -- leave events we can't report right now as pending, so that the next resume picks them up. Note all this ammounts to a QoI change, within the existing framework. There's really no RSP change here. The only user visible change (other than that the signal is program is stopped at isn't lost / is passed to the program), is in "info program", that now can show the signal the program stopped for. Of course, the next resume will respect the pass/nopass setting for the signal in question. It'd be reasonable to have the initial connection tell the user the program was stopped with a signal, similar to when we load a core to debug, but I'm leaving that out for a future change. I think we'll need to either change how handle_inferior_event & co handle stop_soon, or maybe bypass them completely (like fork-child.c:startup_inferior) for that. Tested on x86_64 Fedora 17. gdb/gdbserver/ 2014-01-08 Pedro Alves <palves@redhat.com> * gdbthread.h (struct thread_info) <status_pending_p>: New field. * server.c (visit_actioned_threads, handle_pending_status): New function. (handle_v_cont): Factor out parts to ... (resume): ... this new function. If in all-stop, and a thread being resumed has a pending status, report it without actually resuming. (myresume): Adjust to use the new 'resume' function. (clear_pending_status_callback, set_pending_status_callback) (find_status_pending_thread_callback): New functions. (handle_status): Handle the case of multiple threads having interesting statuses to report. Report threads' real last signal instead of always reporting GDB_SIGNAL_TRAP. Look for a thread with an interesting thread to report the status for, instead of always reporting the status of the first thread. gdb/ 2014-01-08 Pedro Alves <palves@redhat.com> * remote.c (remote_add_thread): Add threads silently if starting up. (remote_notice_new_inferior): If in all-stop, and starting up, don't call notice_new_inferior. (get_current_thread): New function, factored out from ... (add_current_inferior_and_thread): ... this. Adjust. (remote_start_remote) <all-stop>: Fetch the thread list. If we found any thread, then select the remote's current thread as GDB's current thread too. gdb/testsuite/ 2014-01-08 Pedro Alves <palves@redhat.com> * gdb.threads/reconnect-signal.c: New file. * gdb.threads/reconnect-signal.exp: New file.
2014-01-08 18:55:51 +00:00
/* This testcase is part of GDB, the GNU debugger.
Copyright 2013-2016 Free Software Foundation, Inc.
[remote/gdbserver] Don't lose signals when reconnecting. Currently, when GDB connects in all-stop mode, GDBserver always responds to the status packet with a GDB_SIGNAL_TRAP, even if the program is actually stopped for some other signal. (gdb) tar rem ... ... (gdb) c Program received signal SIGUSR1, User defined signal 1. (gdb) disconnect (gdb) tar rem ... (gdb) c (Or a GDB crash instead of an explicit disconnect.) This results in the program losing that signal on that last continue, because gdb will tell the target to resume with no signal (to suppress the GDB_SIGNAL_TRAP, due to 'handle SISGTRAP nopass'), and that will actually suppress the real signal the program had stopped for (SIGUSR1). To fix that, I think we should make GDBserver report the real signal the thread had stopped for in response to the status packet: @item ? @cindex @samp{?} packet Indicate the reason the target halted. The reply is the same as for step and continue. But, that raises the question -- which thread are we reporting the status for? Due to how the RSP in all-stop works, we can only report one status. The status packet's response is a stop reply packet, so it includes the thread identifier, so it's not a problem packet-wise. However, GDBserver is currently always reporting the status for first thread in the thread list, even though that may well not be the thread that got the signal that caused the program to stop. So the next logical step would be to report the status for the last_ptid/last_status thread (the last event reported to gdb), if it's still around; and if not, fallback to some other thread. There's an issue on the GDB side with that, though... GDB currently always adds the thread reported in response to the status query as the first thread in its list. That means that if we start with e.g., (gdb) info threads 3 Thread 1003 ... * 2 Thread 1002 ... 1 Thread 1001 ... And reconnect: (gdb) disconnect (gdb) tar rem ... We end up with: (gdb) info threads 3 Thread 1003 ... 2 Thread 1001 ... * 1 Thread 1002 ... Not a real big issue, but it's reasonably fixable, by having GDB fetch/sync the thread list before fetching the status/'?', and then using the status to select the right thread as current on the GDB side. Holes in the thread numbers are squashed before/after reconnection (e.g., 2,3,5 becomes 1,2,3), but the order is preserved, which I think is both good, and good enough. However (yes, there's more...), the previous GDB that was connected might have had gdbserver running in non-stop mode, or could have left gdbserver doing disconnected tracing (which also forces non-stop), and if the new gdb/connection is in all-stop mode, we can end up with more than one thread with a signal to report back to gdb. As we can only report one thread/status (in the all-stop RSP variant; the non-stop variant doesn't have this issue), we get to do what we do at every other place we have this situation -- leave events we can't report right now as pending, so that the next resume picks them up. Note all this ammounts to a QoI change, within the existing framework. There's really no RSP change here. The only user visible change (other than that the signal is program is stopped at isn't lost / is passed to the program), is in "info program", that now can show the signal the program stopped for. Of course, the next resume will respect the pass/nopass setting for the signal in question. It'd be reasonable to have the initial connection tell the user the program was stopped with a signal, similar to when we load a core to debug, but I'm leaving that out for a future change. I think we'll need to either change how handle_inferior_event & co handle stop_soon, or maybe bypass them completely (like fork-child.c:startup_inferior) for that. Tested on x86_64 Fedora 17. gdb/gdbserver/ 2014-01-08 Pedro Alves <palves@redhat.com> * gdbthread.h (struct thread_info) <status_pending_p>: New field. * server.c (visit_actioned_threads, handle_pending_status): New function. (handle_v_cont): Factor out parts to ... (resume): ... this new function. If in all-stop, and a thread being resumed has a pending status, report it without actually resuming. (myresume): Adjust to use the new 'resume' function. (clear_pending_status_callback, set_pending_status_callback) (find_status_pending_thread_callback): New functions. (handle_status): Handle the case of multiple threads having interesting statuses to report. Report threads' real last signal instead of always reporting GDB_SIGNAL_TRAP. Look for a thread with an interesting thread to report the status for, instead of always reporting the status of the first thread. gdb/ 2014-01-08 Pedro Alves <palves@redhat.com> * remote.c (remote_add_thread): Add threads silently if starting up. (remote_notice_new_inferior): If in all-stop, and starting up, don't call notice_new_inferior. (get_current_thread): New function, factored out from ... (add_current_inferior_and_thread): ... this. Adjust. (remote_start_remote) <all-stop>: Fetch the thread list. If we found any thread, then select the remote's current thread as GDB's current thread too. gdb/testsuite/ 2014-01-08 Pedro Alves <palves@redhat.com> * gdb.threads/reconnect-signal.c: New file. * gdb.threads/reconnect-signal.exp: New file.
2014-01-08 18:55:51 +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 <pthread.h>
#include <signal.h>
#include <unistd.h>
static pthread_t thread_2;
sig_atomic_t unlocked;
/* The test has three threads, and it's always thread 2 that gets the
signal, to avoid spurious passes in case the remote side happens to
always pick the first or the last thread in the list as the
current/status thread on reconnection. */
static void *
start2 (void *arg)
{
unsigned int count;
pthread_kill (thread_2, SIGUSR1);
for (count = 1; !unlocked && count != 0; count++)
usleep (1);
return NULL;
}
static void *
start (void *arg)
{
pthread_t thread;
pthread_create (&thread, NULL, start2, NULL);
pthread_join (thread, NULL);
return NULL;
}
void
handle (int sig)
{
unlocked = 1;
}
int
main ()
{
signal (SIGUSR1, handle);
pthread_create (&thread_2, NULL, start, NULL);
pthread_join (thread_2, NULL);
return 0;
}