Re: ptrace improvement: PTRACE_O_INHERIT

[Roland McGrath <roland@redhat.com>]

> Could PTRACE_ATTACH_NOSTOP+PTRACE_DETACH_NOSTOP? act on the whole PID at once
> if PTRACE_O_THREAD_INHERIT is applied - already during PTRACE_ATTACH_NOSTOP?
> It is a bit overloading the *_NOSTOP meaning but it is a new PTRACE_* op.

This is an obviously desireable feature.  I considered it when making my
suggestions, but stopped short of suggesting it because I think it may have
substantially difficult implementation issues in the kernel.  It may well
be that that detach-group is not really very hard to do at all (that
probably being asynchronous detach, not requiring stopped tracees, and not
supporting any parting-signal feature).  Perhaps attach-group is also more
tractable than I thought from a brief consideration of the implementation
issues.  Oleg will have to study it and give his opinions.  It was my guess
that even if it's pretty doable, the attach-group implementation will be
sufficiently hairy that the kernel community would demand that we do some
simpler incremental changes first before attempting it (such as what I
proposed for ATTACH_NOSTOP, which eliminates the SIGSTOP and rolls in
atomic option-setting).


Thanks,
Roland