From: Oleg Nesterov <oleg@redhat.com>
To: Roland McGrath <roland@redhat.com>
Cc: Project Archer <archer@sourceware.org>
Subject: Re: ptrace improvement: PTRACE_O_INHERIT
Date: Fri, 11 Feb 2011 20:46:00 -0000 [thread overview]
Message-ID: <20110211203755.GA5367@redhat.com> (raw)
In-Reply-To: <20110211192423.78FFC1802A2@magilla.sf.frob.com>
On 02/11, Roland McGrath wrote:
>
> > What else? Say, should TIF_SYSCALL_TRACE be copied?
> > Suppose that we try adapt strace to this new option.
>
> Let's talk about the userland interface features here,
Ah, I didn't mean implementation details, sorry.
> For strace as it is, I don't think there is really any benefit to using
> PTRACE_O_INHERIT.
OK.
> Another feature that has made obvious sense for a long time is to have
> PTRACE_O_TRACESYSCALL instead of just PTRACE_SYSCALL
Yes, and that is why I asked about TIF_SYSCALL_TRACE. Because to me
PTRACE_SYSCALL looks like a property/option regardless of implementation
details.
But I agree, this was a bit off-topic.
> > Or. Suppose that clone() under PTRACE_O_INHERIT notifies the tracer
> > (sends SIGCHLD), and the new tracee gets the new PTRACE_O_INHERITed
> > mark. Then we can implement wait(W_WHO_WAS_CLONNED) which clears
> > PTRACE_O_INHERITed and reports the new tracee (just in case, this
> > doesn't need the stopped tracee).
>
> I don't really follow this idea at all, sorry.
I meant, we can intoduce the new W*** flag for do_wait(). If the new
tracee was PTRACE_O_INHERIT'ed, do_wait() returns its pid.
> > Not sure this makes any sense, but how "info treads" can work otherwise?
>
> It can always look as /proc/PID/task/ to enumerate threads.
Well yes, but /proc/PID/task/ is not convenient and reliable.
Especially if we do not trace all threads.
But, again, if this is fine to gdb - forget.
> > Not sure I really understand why this is the problem by itself. Yes, if
> > its ppid == 1, we know that the original parent was traced by us and then
> > it has gone.
>
> [... snip ...]
Hmm... Still can't understans right now, but this doesn't matter:
> > > So perhaps it would be better to have
> > > this be just PTRACE_O_THREAD_INHERIT, where it only applies to CLONE_THREAD
> > > clones.
> >
> > Or we can have both.
>
> Indeed. But I want to add things that GDB is really going to use, not go
> hog-wild on speculative features
Yes, yes, agreed.
Damn. I was so unclear. I tried to say: yes, I think PTRACE_O_THREAD_INHERIT
makes more sense. If nothing else, the tracer doesn't necessarily wants to
follow forks, this can create the unneeded overhead if it only wants to ptrace
the sub-threads.
IOW, I think that we should have both, or PTRACE_O_THREAD_INHERIT only.
Or, this option should take "clone_flags" as an argument.
Oleg.
next prev parent reply other threads:[~2011-02-11 20:46 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-03 22:39 ptrace improvement ideas Roland McGrath
2011-02-04 18:56 ` Oleg Nesterov
2011-02-04 18:58 ` Roland McGrath
2011-02-07 21:11 ` Jan Kratochvil
2011-02-08 1:58 ` Roland McGrath
2011-02-08 20:41 ` Jan Kratochvil
2011-02-09 2:48 ` Roland McGrath
2011-02-08 21:07 ` Oleg Nesterov
2011-02-08 23:18 ` hw_breakpoint userland interface Roland McGrath
2011-02-10 21:03 ` Oleg Nesterov
2011-02-10 21:14 ` Roland McGrath
2011-02-11 20:17 ` Oleg Nesterov
2011-02-10 20:00 ` ptrace improvement: PTRACE_O_INHERIT Oleg Nesterov
2011-02-11 19:24 ` Roland McGrath
2011-02-11 20:46 ` Oleg Nesterov [this message]
2011-02-12 0:59 ` Roland McGrath
2011-02-12 19:11 ` Oleg Nesterov
2011-02-14 19:31 ` Roland McGrath
2011-02-14 19:46 ` Oleg Nesterov
2011-02-15 0:36 ` Roland McGrath
2011-02-15 13:16 ` Oleg Nesterov
2011-02-15 21:43 ` Jan Kratochvil
2011-02-15 21:56 ` Roland McGrath
2011-02-16 19:42 ` Oleg Nesterov
2011-02-16 19:45 ` Roland McGrath
2011-02-16 20:09 ` Oleg Nesterov
2011-02-16 20:16 ` Roland McGrath
2011-02-19 19:48 ` Jan Kratochvil
2011-02-19 20:37 ` Oleg Nesterov
2011-02-20 8:18 ` Jan Kratochvil
2011-02-20 21:05 ` Oleg Nesterov
2011-02-21 19:54 ` Roland McGrath
2011-02-22 19:39 ` Oleg Nesterov
2011-02-22 20:49 ` Roland McGrath
2011-02-22 21:10 ` Oleg Nesterov
2011-02-22 22:16 ` Roland McGrath
2011-02-21 19:44 ` Roland McGrath
2011-02-15 22:02 ` Roland McGrath
2011-02-16 16:02 ` Jan Kratochvil
2011-02-16 18:28 ` Roland McGrath
2011-02-16 20:00 ` Oleg Nesterov
2011-02-16 20:07 ` Roland McGrath
2011-02-16 20:32 ` Oleg Nesterov
2011-02-16 19:48 ` Oleg Nesterov
2011-02-16 20:02 ` Roland McGrath
2011-02-16 20:15 ` Oleg Nesterov
2011-02-16 20:31 ` Roland McGrath
2011-02-16 21:04 ` Oleg Nesterov
2011-02-16 21:51 ` Roland McGrath
2011-02-16 19:38 ` Oleg Nesterov
2011-02-16 19:40 ` Roland McGrath
2011-02-15 22:17 ` Roland McGrath
2011-02-16 20:48 ` Oleg Nesterov
2011-02-16 11:31 ` ptrace improvement ideas (QPassSignals) Jan Kratochvil
2011-02-16 18:36 ` Roland McGrath
2011-02-16 20:21 ` Oleg Nesterov
2011-02-18 20:24 ` Oleg Nesterov
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