Re: [PATCH] Fix for GDB failing to interrupt after run when no PID issued by stub

Yao Qi
2018-02-01T12:48:52Z

Omair Javaid <omair.javaid@linaro.org> writes:

> Heres the gdb log with run (no other command b/w connection and run):
> https://paste.ubuntu.com/26496015/
>

One thing suspicious to me is an empty reply to qXfer:threads:read

w $qXfer:threads:read::0,fff#03
r $l<?xml version="1.0"?>\n<threads>\n</threads>\n#02

OpenOCD claims support "qXfer:threads:read+;", but such reply above may
confuse GDB. In OpenOCD source, I find OpenOCD supports qXfer:threads
unconditionally, but I think it should be changed to support it when
"target->rtos != NULL". This may don't matter.

> Heres the gdb log with continue + run (after we issue a
> continue/interrupt cycle where inferior PID is set and
> inferior->control.stop_soon = NO_STOP_QUIETLY;)
> https://paste.ubuntu.com/26496048/
>

>
> The situation with OpenOCD happens because we ran and set inferior pid
> to null hoping to update it. Later in extended_remote_create_inferior
> called buy run command thread pid gets assigned but we are checking
> inferior->control.stop_soon just before we update the pid and thus it
> remains to STOP_QUIETLY for lifetime of the inferior as this flag is
> only altered by attach command handlers or during call of
> clear_proceed_status

I still don't understand why inferior->control.stop_soon remains
"STOP_QUIETLY", inferior::control::stop_soon is initialized to
NO_STOP_QUIETLY. I even don't see where it is changed to STOP_QUIETLY.

I can understand that GDB check inferior_ptid (try to set
inferior->control.stop_soon) first [1], and then update inferior_ptid
later [2],

if (!have_inferiors ())
{
/* Clean up from the last time we ran, before we mark the target
running again. This will mark breakpoints uninserted, and
get_offsets may insert breakpoints. */
init_thread_list ();
init_wait_for_inferior (); <-- [1]
}

/* vRun's success return is a stop reply. */
stop_reply = run_worked ? rs->buf : NULL;
add_current_inferior_and_thread (stop_reply); <-- [2]

However, current_inferior_ isn't changed at all, and
current_inferior_->control.stop_soon is not changed either
(NO_STOP_QUIETLY). Could you show me where inf->control.stop_soon is
changed from NO_STOP_QUIETLY?

--
Yao (齐尧)