On Tue, 03 Aug 2010 14:24:34 +0200, Oleg Nesterov wrote: > On 08/03, Jan Kratochvil wrote: > > On Wed, 28 Jul 2010 20:17:02 +0200, Oleg Nesterov wrote: > > Trying it with both /bin/sleep and a threaded testcase and I never got a > > crash > > (kernel-2.6.33.6-147.fc13.x86_64 as both host and KVM guest OS). > > To clarify, let me repeat: I never saw such a crash with the real > gdbserver, but this often happens in my testing.
I am also testing it with your ugdb.c and gdbstub. On Tue, 03 Aug 2010 15:14:36 +0200, Oleg Nesterov wrote: > On 08/03, Oleg Nesterov wrote: > > > > So I assumed it is always safe to resend the notification unless gdb already > > sent vStopped. Since it is not clear to me when it makes sense to resend it, > > currently gdbstub does re-send every time /proc/ugdb reports the new event > > (T00 in this case). I agree this is not optimal, but this looks correct to > > me. > > I'll change gdbstub to never resend the notification to avoid the problem. Yes, I has been now just writing you such reply. > But probably gdb should be fixed anyway. There are so many serious bugs in GDB affecting regular GDB usage... > To avoid the unnecessary details, consider the oversimplified example, > > $ sleep 10000& > [1] 2923 > > $ cat > SLEEP > set target-async on > set non-stop > target extended-remote :2000 > file /bin/sleep > attach 2923 > info registers > detach > ^D > > $ gdb <SLEEP > GNU gdb (GDB) 7.1 > Copyright (C) 2010 Free Software Foundation, Inc. > License GPLv3+: GNU GPL version 3 or later > <http://gnu.org/licenses/gpl.html> > This is free software: you are free to change and redistribute it. > There is NO WARRANTY, to the extent permitted by law. Type "show > copying" > and "show warranty" for details. > This GDB was configured as "x86_64-unknown-linux-gnu". > For bug reporting instructions, please see: > <http://www.gnu.org/software/gdb/bugs/>. > (gdb) (gdb) (gdb) Remote debugging using :2000 > (gdb) Reading symbols from /bin/sleep...(no debugging symbols > found)...done. > (gdb) Attached to process 2923 > [New Thread 2923.2923] > Target is executing. > (gdb) Detached from remote process 2923. > (gdb) quit > > And yes, gdb ignores %Stop and just detaches. But this is because > of another issue (which looks like a minor gdb bug to me), note the > > "Target is executing." > > above. This is the reply to "info registers". Why? OK, yes, it is > executing. Yes. > Then send vCont:t ? "attach PID" means attach and stop it, no? But it is not yet stopped that time. > Can't resist, I spent a lot of time trying to understand what is wrong. Nothing, you should wait till GDB reports the inferior has stopped. It is easy/normal in the GDB testsuite and by FE (Front Ends). I understand it is not convenient from -ex or -x argument. There could be probably some async-only command besides `interrupts', also some `wait-till-stopped'. > I tried to achieve the same results with /proc/ugdb doing > "$ gdb < BATCH_FILE" with the same commands. Maybe you can write a new *.exp testcase for such testing. Thanks, Jan
