Restart remote application

[Petr Koloros <pko@sysgo.com>]

Hi all,

I'm having problems with restarting the remote application. Some time ago it
was advised to use extended protocol and 'run' command but it doesn't work.

(gdb) set debug remote 1
(gdb) target extended-remote 192.168.14.2:5555
.. a lot of packets ..
(gdb) run
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Sending packet: $k#6b...Ack
Starting program: /usr/bin/top 
Sending packet: $R0#82...Ack
Sending packet: $?#3f...Sending packet: $?#3f...Sending packet:
$?#3f...Sending packet: $?#3f...Timed out.
Timed out.
Timed out.


There is no answer from the gdbserver any more because it is in the endless
loop:

recv(4, "$k#6b", 8192, 0)               = 5
send(4, "+", 1, 0)                      = 1
--- SIGIO (I/O possible) @ 0 (0) ---
write(2, "Killing inferior\n", 17)      = 17
ptrace(PTRACE_KILL, 2706, 0, 0)         = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
waitpid(2706, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGKILL}], WNOHANG) = 2706

'k' command from the remote protocol causes the debugged application to be
killed.

write(2, "GDBserver restarting\n", 21)  = 21
rt_sigaction(SIGTTOU, {SIG_DFL}, {SIG_IGN}, 8) = 0
rt_sigaction(SIGTTIN, {SIG_DFL}, {SIG_IGN}, 8) = 0
clone(child_stack=0, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD,
child_tidptr=0xb7dc8b08) = 2709
write(2, "Process /usr/bin/top created; pi"..., 41) = 41
--- SIGCHLD (Child exited) @ 0 (0) ---
rt_sigaction(SIGTTOU, {SIG_IGN}, {SIG_DFL}, 8) = 0
rt_sigaction(SIGTTIN, {SIG_IGN}, {SIG_DFL}, 8) = 0
ioctl(2, TIOCGPGRP, [2706])             = 0
ioctl(2, TIOCSPGRP, [2709])             = 0
rt_sigaction(SIGIO, {0x804c080, [IO], SA_RESTART}, {SIG_IGN}, 8) = 0
rt_sigprocmask(SIG_UNBLOCK, [IO], NULL, 8) = 0
waitpid(-1, [{WIFSTOPPED(s) && WSTOPSIG(s) == SIGTRAP}], WNOHANG) = 2709
ptrace(PTRACE_GETREGS, 2709, 0, 0x8059650) = 0
ptrace(PTRACE_GETFPXREGS, 2709, 0, 0x8059698) = 0
ptrace(PTRACE_GETFPREGS, 2709, 0, 0x80598a0) = 0
ptrace(PTRACE_PEEKTEXT, 2709, 0xb7fe080c, [0]) = 0
rt_sigaction(SIGIO, {SIG_IGN}, {0x804c080, [IO], SA_RESTART}, 8) = 0

Then a 'restart' command arrives in the remote protocol

recv(4, "$R0#82", 8192, 0)              = 6
send(4, "+", 1, 0)                      = 1
--- SIGIO (I/O possible) @ 0 (0) ---
ptrace(PTRACE_KILL, 2709, 0, 0)         = 0
--- SIGCHLD (Child exited) @ 0 (0) ---
waitpid(2709, [{WIFSIGNALED(s) && WTERMSIG(s) == SIGKILL}], WNOHANG) = 2709

..  and because the pid was not cleaned up by extended_remote_mourn:

static void
extended_remote_mourn (void)
{
  /* We do _not_ want to mourn the target like this; this will
     remove the extended remote target  from the target stack,
     and the next time the user says "run" it'll fail.

     FIXME: What is the right thing to do here?  */
#if 0
  remote_mourn_1 (&extended_remote_ops);
#endif
}

ptrace(PTRACE_KILL, 2706, 0, 0)         = -1 ESRCH (No such process)
waitpid(2706, 0xbf877128, WNOHANG)      = -1 ECHILD (No child processes)
waitpid(2706, 0xbf877128, WNOHANG|__WCLONE) = -1 ECHILD (No child processes)

.. it just kills it again and wait for the status which never comes:

nanosleep({0, 1000000}, NULL)           = 0
waitpid(2706, 0xbf877128, WNOHANG)      = -1 ECHILD (No child processes)
waitpid(2706, 0xbf877128, WNOHANG|__WCLONE) = -1 ECHILD (No child processes)
nanosleep({0, 1000000}, NULL)           = 0
waitpid(2706, 0xbf877128, WNOHANG)      = -1 ECHILD (No child processes)
waitpid(2706, 0xbf877128, WNOHANG|__WCLONE) = -1 ECHILD (No child processes)

.. endless loop.

It worked in the past I believe and it doesn't now. Is there some other way
please?


Thanks for your help,

Petr Koloros