Re: [PATCH] ptrace on stopped processes (2.4)

["Mike Coleman" <mkc+dated+1012446540.067c74@mathdogs.com>]

vic <zandy@cs.wisc.edu> writes:
> From: Mike Coleman <mkc@mathdogs.com>:
> > Also, is this something that used to work?  Or would this be a change in the
> > semantics of ptrace?
> 
> This is a change of semantics at least going back to 2.2.

Okay.  Is it at least backward compatible?  Or are some tools expected to
break?

> > Unless I'm missing something (frequently the case), there are two cases here:
> > (1) the tracer wants to leave the tracee stopped, and (2) the tracer wants the
> > process to continue running in as natural a way as possible, meaning without
> > sending it a SIGCONT (which can cause the SIGCONT signal handler to execute).
> > As things currently stand, we have behavior (2), and (1) is not possible.
> > With your change, we'd have behavior (1), and (2) would not be possible.
> 
> I agree that the ability to do (2) should be preserved, but I don't
> see how this patch breaks it; do you have an example?

No, I was just going by reading the kernel code.  Can you describe how each of
(1) and (2) are accomplished by the ptracing program (with your patch)?

Mike