From: Tejun Heo <tj@kernel.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>,
jan.kratochvil@redhat.com, linux-kernel@vger.kernel.org,
torvalds@linux-foundation.org, akpm@linux-foundation.org
Subject: Re: [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE_ATTACH
Date: Fri, 4 Feb 2011 11:53:43 +0100 [thread overview]
Message-ID: <20110204105343.GA12133@htj.dyndns.org> (raw)
In-Reply-To: <20110203214450.GA29496@redhat.com>
Hello, Oleg, Roland.
On Thu, Feb 03, 2011 at 10:44:50PM +0100, Oleg Nesterov wrote:
> On 02/03, Roland McGrath wrote:
> >
> > IMHO this sort of band-aid does not really help the overall situation.
> > It takes something that is intricate and fiddly and just fiddles it a
> > bit more. Userland will still have to handle older kernels where this
> > behavior is not there. If userland does anything that relies on this
> > new behavior, then it will have to try somehow to figure out which
> > kernel versions have which behavior and adapt, etc.
>
> Absolutely agreed.
>
> As I said, I am not sure this patch makes sense. I only sent it
> because I have to react to the bug report.
>
> > When the old behaviors are unhelpful like this, I think it is really
> > better to add new mechanisms instead.
>
> Agreed!
>
> Can't resist, let me repeat... imho ptrace is unfixable ;)
Hmm... I can't reproduce the problem here, but isn't the problematic
part here the mixing of ptrace and group stop and sliently
transforming group stop into ptrace and ptracer consuming the usual
exit code instead of the ptrace specific one?
Also, I don't agree with the notion that doing something entirely new
would magically solve all the problems. Improvements are achieved
through evolution. For ptrace, the situation definitely is aggravated
by the use of wait and weird interaction with group stop, but the
interaction is inherently complex for debugging facility and most
problems won't automatically go away with new interface.
Actually, I think such approach is significantly harmful to
improvements of the existing code base. Instead of encouraging
investigating the actual problems and making sensible tradeoffs, such
approach discourages making reasonable tradeoffs with the false
expectation that something in the future will magically solve the
problems. In a lot of cases, there are no unicorns. Proceeding
forward while managing damage at reasonable level is usually the right
way to go.
That said, well, there always are exceptions and maybe there are some
rainbow farting unicorns in the ptrace land.
Thanks.
--
tejun
next prev parent reply other threads:[~2011-02-04 10:53 UTC|newest]
Thread overview: 160+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-28 15:08 [PATCHSET] ptrace,signal: group stop / ptrace updates Tejun Heo
2011-01-28 15:08 ` [PATCH 01/10] signal: fix SIGCONT notification code Tejun Heo
2011-01-28 15:08 ` [PATCH 02/10] ptrace: remove the extra wake_up_process() from ptrace_detach() Tejun Heo
2011-01-28 18:46 ` Roland McGrath
2011-01-31 10:38 ` Tejun Heo
2011-02-01 10:26 ` [PATCH] ptrace: use safer wake up on ptrace_detach() Tejun Heo
2011-02-01 13:40 ` Oleg Nesterov
2011-02-01 15:07 ` Tejun Heo
2011-02-01 19:17 ` Oleg Nesterov
2011-02-02 5:31 ` Roland McGrath
2011-02-02 10:35 ` Tejun Heo
2011-02-02 0:27 ` Andrew Morton
2011-02-02 5:33 ` Roland McGrath
2011-02-02 5:38 ` Andrew Morton
2011-02-02 10:34 ` Tejun Heo
2011-02-02 19:33 ` Andrew Morton
2011-02-02 20:01 ` Tejun Heo
2011-02-02 21:40 ` Oleg Nesterov
2011-02-02 5:29 ` Roland McGrath
2011-02-02 5:28 ` [PATCH 02/10] ptrace: remove the extra wake_up_process() from ptrace_detach() Roland McGrath
2011-01-28 15:08 ` [PATCH 03/10] signal: remove superflous try_to_freeze() loop in do_signal_stop() Tejun Heo
2011-01-28 18:46 ` Roland McGrath
2011-01-28 15:08 ` [PATCH 04/10] ptrace: kill tracehook_notify_jctl() Tejun Heo
2011-01-28 21:09 ` Roland McGrath
2011-01-28 15:08 ` [PATCH 05/10] ptrace: add @why to ptrace_stop() Tejun Heo
2011-01-28 18:48 ` Roland McGrath
2011-01-28 15:08 ` [PATCH 06/10] signal: fix premature completion of group stop when interfered by ptrace Tejun Heo
2011-01-28 21:22 ` Roland McGrath
2011-01-31 11:00 ` Tejun Heo
2011-02-02 5:44 ` Roland McGrath
2011-02-02 10:56 ` Tejun Heo
2011-01-28 15:08 ` [PATCH 07/10] signal: use GROUP_STOP_PENDING to stop once for a single group stop Tejun Heo
2011-01-28 15:08 ` [PATCH 08/10] ptrace: participate in group stop from ptrace_stop() iff the task is trapping for " Tejun Heo
2011-01-28 21:30 ` Roland McGrath
2011-01-31 11:26 ` Tejun Heo
2011-02-02 5:57 ` Roland McGrath
2011-02-02 10:53 ` Tejun Heo
2011-02-03 10:02 ` Tejun Heo
2011-02-01 19:36 ` Oleg Nesterov
2011-01-28 15:08 ` [PATCH 09/10] ptrace: make do_signal_stop() use ptrace_stop() if the task is being ptraced Tejun Heo
2011-01-28 15:08 ` [PATCH 10/10] ptrace: clean transitions between TASK_STOPPED and TRACED Tejun Heo
2011-02-03 20:41 ` [PATCH 0/1] (Was: ptrace: clean transitions between TASK_STOPPED and TRACED) Oleg Nesterov
2011-02-03 20:41 ` [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE_ATTACH Oleg Nesterov
2011-02-03 21:36 ` Roland McGrath
2011-02-03 21:44 ` Oleg Nesterov
2011-02-04 10:53 ` Tejun Heo [this message]
2011-02-04 13:04 ` Oleg Nesterov
2011-02-04 14:48 ` Tejun Heo
2011-02-04 17:06 ` Oleg Nesterov
2011-02-05 13:39 ` Tejun Heo
2011-02-07 13:42 ` Oleg Nesterov
2011-02-07 14:11 ` Tejun Heo
2011-02-07 15:37 ` Oleg Nesterov
2011-02-07 16:31 ` Tejun Heo
2011-02-07 17:48 ` Oleg Nesterov
2011-02-09 14:18 ` Tejun Heo
2011-02-09 14:21 ` Tejun Heo
2011-02-09 21:25 ` Oleg Nesterov
2011-02-13 23:01 ` Denys Vlasenko
2011-02-14 9:03 ` Jan Kratochvil
2011-02-14 11:39 ` Denys Vlasenko
2011-02-14 17:32 ` Oleg Nesterov
2011-02-14 16:01 ` Oleg Nesterov
2011-02-26 3:59 ` Pavel Machek
2011-02-14 15:51 ` Oleg Nesterov
2011-02-14 14:50 ` Tejun Heo
2011-02-14 18:53 ` Oleg Nesterov
2011-02-13 22:25 ` Denys Vlasenko
2011-02-14 15:13 ` Tejun Heo
2011-02-14 16:15 ` Oleg Nesterov
2011-02-14 16:33 ` Tejun Heo
2011-02-14 17:23 ` Oleg Nesterov
2011-02-14 17:20 ` Denys Vlasenko
2011-02-14 17:30 ` Tejun Heo
2011-02-14 17:45 ` Oleg Nesterov
2011-02-14 17:54 ` Denys Vlasenko
2011-02-21 15:16 ` Tejun Heo
2011-02-21 15:28 ` Oleg Nesterov
2011-02-21 16:11 ` [pseudo patch] ptrace should respect the group stop Oleg Nesterov
2011-02-22 16:24 ` [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE_ATTACH Tejun Heo
2011-02-24 21:08 ` Oleg Nesterov
2011-02-25 15:45 ` Tejun Heo
2011-02-25 17:42 ` Roland McGrath
2011-02-28 15:23 ` Oleg Nesterov
2011-02-14 17:51 ` Oleg Nesterov
2011-02-14 18:55 ` Denys Vlasenko
2011-02-14 19:01 ` Oleg Nesterov
2011-02-14 19:42 ` Denys Vlasenko
2011-02-14 20:01 ` Oleg Nesterov
2011-02-15 15:24 ` Tejun Heo
2011-02-15 15:58 ` Oleg Nesterov
2011-02-15 17:31 ` Roland McGrath
2011-02-15 20:27 ` Oleg Nesterov
2011-02-18 17:02 ` Tejun Heo
2011-02-18 19:37 ` Oleg Nesterov
2011-02-21 16:22 ` Tejun Heo
2011-02-21 16:49 ` Oleg Nesterov
2011-02-21 16:59 ` Tejun Heo
2011-02-23 19:31 ` Oleg Nesterov
2011-02-25 15:10 ` Tejun Heo
2011-02-24 20:29 ` Oleg Nesterov
2011-02-25 15:51 ` Tejun Heo
2011-02-26 2:48 ` Denys Vlasenko
2011-02-28 12:56 ` Tejun Heo
2011-02-28 13:16 ` Denys Vlasenko
2011-02-28 13:29 ` Tejun Heo
2011-02-28 13:41 ` Denys Vlasenko
2011-02-28 13:53 ` Tejun Heo
2011-02-28 14:25 ` Denys Vlasenko
2011-02-28 14:39 ` Tejun Heo
2011-02-28 16:48 ` Oleg Nesterov
2011-02-28 14:36 ` Oleg Nesterov
2011-02-16 21:51 ` Jan Kratochvil
2011-02-17 3:37 ` Denys Vlasenko
2011-02-17 19:19 ` Oleg Nesterov
2011-02-18 21:11 ` Jan Kratochvil
2011-02-19 20:16 ` Oleg Nesterov
2011-02-17 16:49 ` Oleg Nesterov
2011-02-17 18:58 ` Roland McGrath
2011-02-17 19:33 ` Oleg Nesterov
2011-02-18 21:34 ` Jan Kratochvil
2011-02-19 20:06 ` Oleg Nesterov
2011-02-20 9:40 ` Jan Kratochvil
2011-02-20 17:06 ` Denys Vlasenko
2011-02-20 17:48 ` Oleg Nesterov
2011-02-20 19:10 ` Jan Kratochvil
2011-02-20 19:16 ` Oleg Nesterov
2011-02-20 17:16 ` Oleg Nesterov
2011-02-20 18:52 ` Jan Kratochvil
2011-02-20 20:38 ` Oleg Nesterov
2011-02-20 21:06 ` `(T) stopped' preservation after _exit() [Re: [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE_ATTACH] Jan Kratochvil
2011-02-20 21:19 ` Oleg Nesterov
2011-02-20 21:20 ` [PATCH 1/1] ptrace: make sure do_wait() won't hang after PTRACE_ATTACH Jan Kratochvil
2011-02-21 14:23 ` Oleg Nesterov
2011-02-23 16:44 ` Jan Kratochvil
2011-02-14 15:31 ` Oleg Nesterov
2011-02-14 17:24 ` Denys Vlasenko
2011-02-14 17:39 ` Oleg Nesterov
2011-02-14 17:57 ` Denys Vlasenko
2011-02-14 18:00 ` Oleg Nesterov
2011-02-14 18:06 ` Oleg Nesterov
2011-02-14 18:59 ` Denys Vlasenko
2011-02-13 21:24 ` Denys Vlasenko
2011-02-14 15:06 ` Oleg Nesterov
2011-02-14 15:19 ` Tejun Heo
2011-02-14 16:20 ` Oleg Nesterov
2011-02-14 17:05 ` Denys Vlasenko
2011-02-14 17:18 ` Oleg Nesterov
2011-01-28 16:54 ` [PATCHSET] ptrace,signal: group stop / ptrace updates Ingo Molnar
2011-01-28 17:41 ` Thomas Gleixner
2011-01-28 18:04 ` Anca Emanuel
2011-01-28 18:36 ` Mathieu Desnoyers
2011-01-28 17:55 ` Oleg Nesterov
2011-01-28 18:29 ` Bash not reacting to Ctrl-C Ingo Molnar
2011-02-05 20:34 ` Oleg Nesterov
2011-02-07 13:08 ` Oleg Nesterov
2011-02-09 6:17 ` Michael Witten
2011-02-09 14:53 ` Ingo Molnar
2011-02-09 19:37 ` Michael Witten
2011-02-11 14:41 ` Pavel Machek
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