Re: [RFA 1/2] PR gdb/20604 - fix "quit" when an invalid expression is used

["Ulrich Weigand" <uweigand@de.ibm.com>]

Pedro Alves wrote:
> On 09/20/2016 11:45 PM, Tom Tromey wrote:
> >>>>>> "Pedro" == Pedro Alves <palves@redhat.com> writes:
> > 
> > Pedro> Hi Tom, the gdb code looks fine.  Some comments on the test.
> > 
> > Pedro> Could you try the new test with --host_board=local-remote-host.exp?  
> > Pedro> That should cover at least remote ssh testing, which is what
> > Pedro> most people use nowadays, anyway.  I'd be happy with that.
> > 
> > I tried this today and it worked for me.
> > 
> >>> +close $gdb_spawn_id
> > 
> > Pedro> Maybe just calling clear_gdb_spawn_id at the end is all that's
> > Pedro> necessary?
> > 
> > Seems like a good idea, I made this change locally.
> > 
> 
> OK, thanks.  Fell free to push.  We'll do something about it if it
> causes problems on real remote hosts.

I just noticed that this test case completely breaks my daily testing.
When running the quit.exp test, GDB will hang in a way that it isn't
even killed by the timeout logic, and will keep blocking further
execution forever.

Attaching to GDB shows it blocked in an ioctl with this backtrace
(which for some reason doesn't even include the quit path ...)

#0  0x0feea474 in tcsetattr () from /lib/libc.so.6
#1  0x102d7004 in _set_tty_settings (tty=0, tiop=0x10641adc) at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/readline/rltty.c:476
#2  0x102d70e0 in set_tty_settings (tty=<value optimized out>, tiop=<value optimized out>)
    at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/readline/rltty.c:490
#3  0x102d7530 in rl_deprep_terminal () at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/readline/rltty.c:688
#4  0x102ea2d4 in rl_callback_read_char () at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/readline/callback.c:215
#5  0x1017defc in gdb_rl_callback_read_char_wrapper (client_data=<value optimized out>)
    at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/event-top.c:173
#6  0x1017ecc4 in stdin_event_handler (error=<value optimized out>, client_data=0x10650018)
    at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/event-top.c:505
#7  0x1017d630 in handle_file_event (file_ptr=0x10749238, ready_mask=<value optimized out>)
    at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/event-loop.c:733
#8  0x1017d84c in gdb_wait_for_event (block=0) at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/event-loop.c:884
#9  0x1017dc18 in gdb_do_one_event () at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/event-loop.c:322
#10 0x1017dd20 in start_event_loop () at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/event-loop.c:371
#11 0x10175968 in captured_command_loop (data=<value optimized out>) at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/main.c:325
#12 0x101714a8 in catch_errors(catch_errors_ftype *, void *, char *, ._43) (func=0x10175930 <captured_command_loop(void*)>, func_args=0x0, errstring=0x104ccb4c "", 
    mask=RETURN_MASK_ALL) at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/exceptions.c:236
#13 0x10176f54 in captured_main (args=<value optimized out>) at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/main.c:1145
#14 gdb_main (args=<value optimized out>) at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/main.c:1155
#15 0x10006e28 in main (argc=<value optimized out>, argv=<value optimized out>) at /home/uweigand/dailybuild/spu-tc-2016-10-25/binutils-gdb-head/binutils-gdb/gdb/gdb.c:32

Note that when running GDB directly, quit works fine.  The problem
occurs only when running GDB under the DejaGNU framework.

Does this ring any bells?  Any thoughts what could cause this?

Bye,
Ulrich

-- 
  Dr. Ulrich Weigand
  GNU/Linux compilers and toolchain
  Ulrich.Weigand@de.ibm.com