Re: Single stepping and threads

[Michael Snyder <Michael.Snyder@palmsource.com>]

On Wed, 2006-11-29 at 08:36 -0500, Daniel Jacobowitz wrote:
> On Wed, Nov 29, 2006 at 01:40:49PM +0100, Mark Kettenis wrote:
> > Are you talking about stepi or step?
> > For step we should be very careful, since on some platforms the dynamic
> > linker may play games with locks and we risk a deadlock if we don't let
> > the other threads run.
> 
> That's the second part of the question :-)  The current setting of
> "set scheduler-locking" applies to whenever proceed() is told to step,
> rather than when the user says "step".  So it affects stepi always and
> step within a source line, but not step over a function. 

That was intentional -- a compromise between more stringent locking, 
and the tendency to deadlock.

The idea was, "a function call is too long to keep the scheduler
locked, unles you insist on locking it down completely (schedlock on)".


>  I talked
> about "stepping" over prologues and over functions without debug info;
> I hadn't thought about skipping shared library trampolines, but I
> can definitely see how that would be a problem.
> 
> I don't like the user interface here; we say "step" and it will
> sometimes run one thread and sometimes run all threads and it's hard to
> explain which.  But we may not be able to do better without adding
> unacceptable risk of deadlocks :-(
>