Re: [MI non-stop 03/11, RFA] Discard cleanup when deferring displaced step

[Pedro Alves <pedro at codesourcery dot com>]

A Saturday 28 June 2008 17:39:52, Vladimir Prus wrote:
> My MI non-stop tests (coming later in the series) revealed a bug in
> displaced stepping -- we fail to discard cleanup on an early exit path,
> which caused a call to normal_stop at very unfortunate time -- when a
> thread was running.
>

Ooops, my bad.  Thanks for catching this!

I think it would make sense to tag the thread as running at that point.
In the point of view of the frontend, it is running, but internally,
it is known to not be executing, until its turn in the displaced stepping
request queue arrives.  That is, the frontend should not allow inspecting
this thread as if it was running already, and interrupting it should make
it stop as soon as it tries to execute, not skip over it like ends up
happening currently.

To be clear, the user told the thread to resume, it just didn't resume
immediatelly due to an internal implementation detail.  (is_running (ptid)
&& !is_executing (ptid)) should be true at that early return.  Not a
serious issue to run to fix it (may need care if starting the
displaced step on it ends up failing), but,

Anyone disagrees in principle?

> OK?
>
> - Volodya
>
> 	* infrun.c (resume): Discard cleanups on early exit path.
> ---
>  gdb/infrun.c |   11 +++++++----
>  1 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/gdb/infrun.c b/gdb/infrun.c
> index cf23c18..e803d1b 100644
> --- a/gdb/infrun.c
> +++ b/gdb/infrun.c
> @@ -964,10 +964,13 @@ a command like `return' or `jump' to continue
> execution.")); && sig == TARGET_SIGNAL_0)
>      {
>        if (!displaced_step_prepare (inferior_ptid))
> -	/* Got placed in displaced stepping queue.  Will be resumed
> -	   later when all the currently queued displaced stepping
> -	   requests finish.  */
> -	return;
> +	{
> +	  /* Got placed in displaced stepping queue.  Will be resumed
> +	     later when all the currently queued displaced stepping
> +	     requests finish.  */
> +	  discard_cleanups (old_cleanups);
> +	  return;
> +	}
>      }
>
>    if (step && gdbarch_software_single_step_p (gdbarch))



-- 
Pedro Alves