From: Jan Kratochvil <jan.kratochvil@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Roland McGrath <roland@redhat.com>,
Project Archer <archer@sourceware.org>
Subject: Re: ptrace improvement: PTRACE_O_INHERIT
Date: Sat, 19 Feb 2011 19:48:00 -0000 [thread overview]
Message-ID: <20110219194758.GA8994@host1.dyn.jankratochvil.net> (raw)
In-Reply-To: <20110216200110.GA17601@redhat.com>
On Wed, 16 Feb 2011 21:01:10 +0100, Oleg Nesterov wrote:
> On 02/16, Roland McGrath wrote:
> > If the process-wide PID (tgid) is not reused
> > ...
> > then tgkill does protect completely against TID reuse.
>
> How? sooner or later the process which creates/destroys a thread
> in a loop will reuse some pid number.
(a) GDB tracks separately threads (libpthread-managed) and LWPs (TIDs).
(So the libthread_db TD_DEATH notification is offtopic for this mail.)
(b) For LWPs it does not use PTRACE_O_TRACEEXIT.
/* Do not enable PTRACE_O_TRACEEXIT until GDB is more prepared to support
read-only process state. */
(I do not know more regarding this comment.)
Therefore it occasionally uses tkill (TID, 0) instead of PTRACE_O_TRACEEXIT.
It uses PTRACE_O_TRACECLONE so it should see a reusal of thread TID in the same
PID, although it seems to me it will just create a duplicate {PID, TID}.
Just currently there are enough bugreports about users hitting threading races
of GDB in real world so we do not have to think about more race possibilities.
Thanks,
Jan
next prev parent reply other threads:[~2011-02-19 19:48 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
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 [this message]
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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