Re: Race in ptrace.

[Salman Qazi <sqazi@google.com>]

On Thu, Feb 11, 2010 at 12:55 PM, Roland McGrath <roland@redhat.com> wrote:
>> What I don't agree with is that when we send SIGCONT later with
>> "kill", we wake up the child at all.  It may make sense to someone who
>> has access to the kernel source code, but from a user's point of view
>> this is a surprise.  The signal is intercepted and should not have an
>> effect on the child.
>
> This is the behavior of SIGCONT and doesn't really have anything to do with
> ptrace.  Once you have let the SIGSTOP through, the process is in job
> control stop just like if you'd sent a SIGSTOP without using ptrace at all.
>
> The distinction that is confusing you is that *generating* SIGCONT is what
> resumes the process, not *delivering* it.  Another example is that if your
> process has SIGCONT blocked or ignored, SIGCONT still wakes it up.  Another
> example is that SIGCONT wakes up all the threads in a process, before one
> of those threads delivers the SIGCONT (i.e. runs a handler).

Thanks for the clarification.  This is exactly the bit of information
I was missing.

>
>
> Thanks,
> Roland
>