Re: [PATCH] preventing resuming of threads in gdbserver

[Michael Snyder <msnyder@redhat.com>]

Amit Kale wrote:
> Hi,
> 
> gdb lets other threads continue execution during single stepping when doing a 
> single step in remote mode. This behavior causes thread switches during step 
> or next commands. Native mode behavior is opposite of it. Attached patch 
> changes it and makes it similar to native mode.

Actually, letting other threads continue during single stepping
is the norm.  It happens on almost all multi-thread gdb targets.

Indeed, if you don't allow it to happen, you're risking deadlock,
and certainly changing the program behavior.

Moreover, a patch that changes the behavior of *all* remote targets
is going to be challenging to get approved.



On the other hand, there is a user-setable mode variable
called "scheduler-locking", which is meant to have the exact
effect you are looking for.  If you wanted to re-do your patch
so that it made this change conditionally, under the control of
that variable, it might be more acceptable.


> ------------------------------------------------------------------------
> 
> Index: gdb-cvs/gdb/remote.c
> ===================================================================
> --- gdb-cvs.orig/gdb/remote.c	2006-01-03 11:24:35.000000000 +0530
> +++ gdb-cvs/gdb/remote.c	2006-01-10 18:00:05.000000000 +0530
> @@ -2519,10 +2519,10 @@
>      {
>        /* Resume all threads, with preference for INFERIOR_PTID.  */
>        if (step && siggnal != TARGET_SIGNAL_0)
> -	outbuf = xstrprintf ("vCont;S%02x:%x;c", siggnal,
> +	outbuf = xstrprintf ("vCont;S%02x:%x", siggnal,
>  			     PIDGET (inferior_ptid));
>        else if (step)
> -	outbuf = xstrprintf ("vCont;s:%x;c", PIDGET (inferior_ptid));
> +	outbuf = xstrprintf ("vCont;s:%x", PIDGET (inferior_ptid));
>        else if (siggnal != TARGET_SIGNAL_0)
>  	outbuf = xstrprintf ("vCont;C%02x:%x;c", siggnal,
>  			     PIDGET (inferior_ptid));