From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: roland@redhat.com, linux-kernel@vger.kernel.org,
torvalds@linux-foundation.org, akpm@linux-foundation.org,
rjw@sisk.pl, jan.kratochvil@redhat.com
Subject: Re: [PATCH 10/16] ptrace: clean transitions between TASK_STOPPED and TRACED
Date: Wed, 22 Dec 2010 17:00:16 +0100 [thread overview]
Message-ID: <20101222160016.GA11722@redhat.com> (raw)
In-Reply-To: <20101222151429.GC8061@htj.dyndns.org>
On 12/22, Tejun Heo wrote:
>
> On Wed, Dec 22, 2010 at 12:39:48PM +0100, Oleg Nesterov wrote:
> >
> > sys_ptrace() only works for the single thread who did PTRACE_ATTACH,
> > but do_wait() should work for its sub-threads.
> >
> > 1. the tracer knows that the tracee is stopped
> >
> > 2. the tracer does ptrace(ATTACH)
> >
> > 3. the tracer's sub-thread does do_wait()
> >
> > Note! Personally I think we can ignore this "problem", I do not
> > think it can break anything except some specialized test-case.
>
> But if ptrace(ATTACH) doesn't return until the transition is complete
> when the task is already stopped, the tracer's sub-thread's do_wait()
> will behave exactly the same. The only difference would be that
> ptrace(ATTACH) may now block and/or is failed by a signal delivery.
>
> How would #3 behave differently if STOPPED -> TRACED transition is
> guaranteed to be complete by the end of #2?
Ahhh, sorry. I meant, two threads can do 2. and 3. at the same time.
But let me repeat, it is not that I think we should worry. I mentioned
this only because I think it is better to discuss everything we can,
even the really minor things.
Oleg.
next prev parent reply other threads:[~2010-12-22 16:07 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-06 16:56 [PATCHSET] ptrace,signal: sane interaction between ptrace and job control signals, take#2 Tejun Heo
2010-12-06 16:56 ` [PATCH 01/16] signal: fix SIGCONT notification code Tejun Heo
2010-12-06 16:56 ` [PATCH 02/16] signal: fix CLD_CONTINUED notification target Tejun Heo
2010-12-20 14:58 ` Oleg Nesterov
2010-12-21 16:31 ` Tejun Heo
2010-12-06 16:56 ` [PATCH 03/16] signal: remove superflous try_to_freeze() loop in do_signal_stop() Tejun Heo
2010-12-20 14:59 ` Oleg Nesterov
2010-12-06 16:56 ` [PATCH 04/16] ptrace: kill tracehook_notify_jctl() Tejun Heo
2010-12-20 14:59 ` Oleg Nesterov
2010-12-21 17:00 ` Tejun Heo
2010-12-06 16:56 ` [PATCH 05/16] ptrace: add @why to ptrace_stop() Tejun Heo
2010-12-06 16:56 ` [PATCH 06/16] signal: fix premature completion of group stop when interfered by ptrace Tejun Heo
2010-12-20 15:00 ` Oleg Nesterov
2010-12-21 17:04 ` Tejun Heo
2010-12-06 16:56 ` [PATCH 07/16] signal: use GROUP_STOP_PENDING to stop once for a single group stop Tejun Heo
2010-12-06 16:56 ` [PATCH 08/16] ptrace: participate in group stop from ptrace_stop() iff the task is trapping for " Tejun Heo
2010-12-06 16:56 ` [PATCH 09/16] ptrace: make do_signal_stop() use ptrace_stop() if the task is being ptraced Tejun Heo
2010-12-23 12:26 ` Oleg Nesterov
2010-12-23 13:53 ` Tejun Heo
2010-12-23 16:06 ` Oleg Nesterov
2010-12-23 16:33 ` Tejun Heo
2011-01-17 22:09 ` Roland McGrath
2011-01-27 13:56 ` Tejun Heo
2011-01-28 20:30 ` Roland McGrath
2011-01-31 14:39 ` Tejun Heo
2010-12-06 16:56 ` [PATCH 10/16] ptrace: clean transitions between TASK_STOPPED and TRACED Tejun Heo
2010-12-20 15:00 ` Oleg Nesterov
2010-12-21 17:31 ` Tejun Heo
2010-12-21 17:32 ` Tejun Heo
2010-12-22 10:54 ` Tejun Heo
2010-12-22 11:39 ` Oleg Nesterov
2010-12-22 15:14 ` Tejun Heo
2010-12-22 16:00 ` Oleg Nesterov [this message]
2010-12-22 16:21 ` Tejun Heo
2010-12-06 16:56 ` [PATCH 11/16] signal: prepare for CLD_* notification changes Tejun Heo
2010-12-20 16:21 ` Oleg Nesterov
2010-12-20 16:23 ` Oleg Nesterov
2010-12-21 17:35 ` Tejun Heo
2010-12-06 16:57 ` [PATCH 12/16] ptrace: make group stop notification reliable against ptrace Tejun Heo
2010-12-20 17:34 ` Oleg Nesterov
2010-12-21 17:43 ` Tejun Heo
2010-12-22 11:54 ` Oleg Nesterov
2010-12-22 15:26 ` Tejun Heo
2010-12-22 16:02 ` Oleg Nesterov
2010-12-06 16:57 ` [PATCH 13/16] ptrace: reorganize __ptrace_unlink() and ptrace_untrace() Tejun Heo
2010-12-20 18:15 ` Oleg Nesterov
2010-12-21 17:54 ` Tejun Heo
2010-12-06 16:57 ` [PATCH 14/16] ptrace: make SIGCONT notification reliable against ptrace Tejun Heo
2010-12-20 19:43 ` Oleg Nesterov
2010-12-21 17:48 ` Tejun Heo
2010-12-22 12:16 ` Oleg Nesterov
2010-12-21 17:25 ` Oleg Nesterov
2010-12-22 10:35 ` Tejun Heo
2010-12-06 16:57 ` [PATCH 15/16] ptrace: make sure SIGNAL_NOTIFY_CONT is checked after ptrace_signal() Tejun Heo
2010-12-06 16:57 ` [PATCH 16/16] ptrace: remove the extra wake_up_process() from ptrace_detach() Tejun Heo
2010-12-07 0:10 ` Roland McGrath
2010-12-07 13:43 ` Tejun Heo
2010-12-21 17:54 ` Oleg Nesterov
2010-12-22 10:36 ` Tejun Heo
2010-12-14 17:36 ` [PATCHSET] ptrace,signal: sane interaction between ptrace and job control signals, take#2 Oleg Nesterov
2010-12-14 17:46 ` Tejun Heo
2010-12-22 15:20 ` Oleg Nesterov
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