Re: [PATCH V2 0/5] Support tracepoints for ARM linux in GDBServer

[Antoine Tremblay <antoine dot tremblay at ericsson dot com>]

Yao Qi writes:

> On Tue, Nov 8, 2016 at 1:28 AM, Antoine Tremblay
> <antoine.tremblay@ericsson.com> wrote:
>>
>
>>>
>>> I am still testing arm-linux gdbserver without and with software
>>> single step.  I still see some intermittent regressions _with_
>>> software single step,
>>>
>>> +FAIL: gdb.threads/non-stop-fair-events.exp: signal_thread=8: thread 1
>>> broke out of loop (timeout)
>>> +FAIL: gdb.threads/schedlock.exp: schedlock=off: cmd=step: step to
>>> increment (1) (timeout)
>>>
>>
>> I have not seen that except when I get random SIGILLs, I'll try to run
>> these more often and see if I can reproduce it.
>>
>
> I have two boards for testing pandaboard (3.4.0-2-linaro-lt-omap)
> and chromebook (4.7.2).  I got non-stop-fair-events.exp timeout
> from time to time, you can get gdb.log here,
> http://people.linaro.org/~yao.qi/gdb/arm-linux-tracepoint/non-stop-fair-events/
>
> I can also see SIGILL or SIGSEGV in schedlock.exp,
> http://people.linaro.org/~yao.qi/gdb/arm-linux-tracepoint/schedlock/
>
> if I hack gdbserver/linux-low.c to disable software single step,
>  static int
>  can_software_single_step (void)
>  {
> -  return (the_low_target.get_next_pcs != NULL);
> +  return 0/*(the_low_target.get_next_pcs != NULL)*/;
>  }
>
> the fails goes away.
>

OK, thanks for the description, I can now reproduce it on my Odroid UX4
and I have a good idea where the problem is now (some cases of
installing the software breakpoitns are done without stopping the threads).

So I should be able to fix this soon.

>>> This reveals something wrong in software single step in GDBserver.
>>> I don't think we should bring tracepoint in until these regressions are
>>> fixed.I won't work on these regressions until next pre-release.  If
>>> you can reproduce them and help to fix them, that will be great.
>>
>> I will do my best to fix these issues asap,
>>
>> However I would very much like if we could still start the review
>> process on the tracing.
>
> I'll play with them, and give some review later.

Thank you very much, hopefully I'll have the fix for the issue by then
too.

Antoine