Re: [PATCH] Bail out of processing stop if hook-stop resumes target / changes context

[Yao Qi <qiyaoltc at gmail dot com>]

Pedro Alves <palves@redhat.com> writes:

>>> -  if (stop_command)
>>> -    catch_errors (hook_stop_stub, stop_command,
>>> -		  "Error while running hook_stop:\n", RETURN_MASK_ALL);
>>> +  if (stop_command != NULL)
>>> +    {
>>> +      struct stop_context *saved_context = save_stop_context ();
>>> +      struct cleanup *old_chain
>>> +	= make_cleanup (release_stop_context_cleanup, saved_context);
>>> +
>>> +      catch_errors (hook_stop_stub, stop_command,
>>> +		    "Error while running hook_stop:\n", RETURN_MASK_ALL);
>>> +
>>> +      /* If the stop hook resumes the target, then there's no point in
>>> +	 trying to notify about the previous stop; its context is
>>> +	 gone.  Likewise if the command switches thread or inferior --
>>> +	 the observers would print a stop for the wrong
>>> +	 thread/inferior.  */
>>> +      if (stop_context_changed (saved_context))
>>> +	{
>>> +	  do_cleanups (old_chain);
>>> +	  return 1;
>>> +	}
>>> +      do_cleanups (old_chain);
>>> +    }
>> 
>> I am wondering why don't we let interpreter in async to execute
>> stop_command, and we simply return here.  In this way, we don't have to
>> know whether stop_command resumes the target or switches the thread.
>> Once there is no event from event loop, the target really stops and
>> hook-stop is already executed.
>
> Not sure I understood the suggestion -- I don't see how that would end
> up being different.  If the hook-stop does "continue&", then we still need
> to know that the target was resumed.  Likewise if the hook-stop just
> does "thread N" and thus switches to another thread -- there's no
> execution involved in that case so seems to me interpreter async/sync
> makes no difference.

I was thinking that why do we need stop_id or stop_context here.  We can
let interpreter to execute hook-stop commands in an async way, and GDB
reads events out of event loop, until all events are consumed.  In this
way, do we still need stop_id or stop_context?

-- 
Yao (éå)