Re: The threads saga: watchpoints

[Daniel Jacobowitz <drow@mvista.com>]

On Fri, Mar 07, 2003 at 09:41:33AM -0500, Elena Zannoni wrote:
> Daniel Jacobowitz writes:
>  > It was pointed out to me today that watchpoints and threads really don't get
>  > along.  It's even in the manual:
>  > 
>  >      _Warning:_ In multi-thread programs, watchpoints have only limited
>  >      usefulness.  With the current watchpoint implementation, GDB can
>  >      only watch the value of an expression _in a single thread_.  If
>  >      you are confident that the expression can only change due to the
>  >      current thread's activity (and if you are also confident that no
>  >      other thread can become current), then you can use watchpoints as
>  >      usual.  However, GDB may not notice when a non-current thread's
>  >      activity changes the expression.
>  > 
>  > 
>  > I think some of our hardware breakpoint implementations have the same issue.
>  > 
>  > It seems to me that, in general, this should be pretty easy to fix.  But it
>  > requires some definite changes in the current infrastructure.  Shouldn't we
>  > be able to insert the watchpoint in all threads?
>  > 
>  > -- 
>  > Daniel Jacobowitz
>  > MontaVista Software                         Debian GNU/Linux Developer
> 
> 
> There was a discussion on this some time ago:
> 
> http://sources.redhat.com/ml/gdb-patches/2002-01/msg00383.html
> and follow-ups.

Thanks!  I missed that one.  I think that perhaps I should audit the
available hardware watchpoint mechanisms for similar problems...

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer