Re: [bug?] [patch] target remote and multiprocess+

[Luis Machado <lgustavo@codesourcery.com>]

Hi,

On 11/23/2016 02:55 AM, Matthias Pfaller wrote:
> To make sure I'm not totally wrong I did run an (unpatched) gdbserver
> (7.11.1) -multi on my host machine. Then I connected with
> extended-remote and created two inferiors. After a disconnect and a
> reconnect gdbserver responds with the following inferior/thread list:
>
> l<threads>\n<thread id="p29ae.29ae" core="3" name="xterm"/>\n<thread
> id="p3dcf.3dcf" core="1" name="xterm"/>\n</threads>\n
>
> But doing a "info inferiors" will show:
> (gdb) info inferiors
>   Num  Description       Executable
> * 1    process 15823     /usr/uti/xterm
>
> and info threads:
> (gdb) info threads
> Sending packet: $qXfer:threads:read::0,fff#03...Packet received:
> l<threads>\n<thread id="p29ae.29ae" core="3" name="xterm"/>\n<thread
> id="p3dcf.3dcf" core="1" name="xterm"/>\n</threads>\n
>   Id   Target Id         Frame
>   1    Thread 10670.10670 "xterm"
> ../../gdb/thread.c:1447: internal-error: switch_to_thread: Assertion
> `inf != NULL' failed.
> A problem internal to GDB has been detected,
> further debugging may prove unreliable.
> Quit this debugging session? (y or n)
>
> (note that this is the host system's gdb 7.11.1)
> So attaching to a target with multiple running inferiors just doesn't
> work at the moment.
>
> Now I tried with gdb-7.12 and my patches applied:
>
> (gdb) set non-stop on
> (gdb) target remote localhost:29979
> Remote debugging using localhost:29979
> Reading /usr/uti/xterm from remote target...
> warning: File transfers from remote targets can be slow. Use "set
> sysroot" to access files locally instead.
> Reading /usr/uti/xterm from remote target...
> Reading symbols from target:/usr/uti/xterm...(no debugging symbols
> found)...done.
> Python Exception <type 'exceptions.NameError'> Installation error:
> gdb.execute_unwinders function is missing:
>
> Thread 1.1 "xterm" stopped.
> 0x00007ffff7ddac80 in ?? ()
> Python Exception <type 'exceptions.NameError'> Installation error:
> gdb.execute_unwinders function is missing:
>
> Thread 2.1 "xterm" stopped.
> 0x00007ffff7ddac80 in ?? ()
> (gdb) info threads
>   Id   Target Id         Frame
>   1.1  Thread 10670.10670 "xterm" Python Exception <type
> 'exceptions.NameError'> Installation error: gdb.execute_unwinders
> function is missing:
> 0x00007ffff7ddac80 in ?? ()
> * 2.1  Thread 15823.15823 "xterm" Python Exception <type
> 'exceptions.NameError'> Installation error: gdb.execute_unwinders
> function is missing:
> 0x00007ffff7ddac80 in ?? ()
> (gdb) info inferiors
>   Num  Description       Executable
>   1    process 10670     target:/usr/uti/xterm
> * 2    process 15823     target:/usr/uti/xterm
>
> So I think this is at least not worse than what gdb was doing before...
> Is there a chance to get this patch into gdb?
>
> Matthias
>

I think i misunderstood your initial explanation. So the patch in 
questions attempts to fix the internal error plus the fact that GDB 
doesn't show more than one inferior when connecting to a gdbserver that 
is controlling multiple inferiors?

If so, indeed it is a bug and i still see it on master GDB. I'd send the 
patch to gdb-patches so we can properly review it.

Also, did you run the gdb testsuite to make sure your patch did not 
introduce regressions comparing against the unpatch gdb testsuite run?

You can run the testsuite like this:

make check-gdb (top-level) or make-gdb

You should also run the testsuite against gdbserver like this:

make check-gdb RUNTESTFLAGS="--target_board native-gdbserver"