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From: Pedro Alves <pedro@codesourcery.com>
To: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Tejun Heo <tj@kernel.org>,
	oleg@redhat.com, jan.kratochvil@redhat.com,
	linux-kernel@vger.kernel.org, torvalds@linux-foundation.org,
	akpm@linux-foundation.org, indan@nul.nu, bdonlan@gmail.com
Subject: Re: [PATCH 03/10] ptrace: implement PTRACE_SEIZE
Date: Fri, 20 May 2011 09:56:22 +0100	[thread overview]
Message-ID: <201105200956.23320.pedro@codesourcery.com> (raw)
In-Reply-To: <201105200344.44520.vda.linux@googlemail.com>

On Friday 20 May 2011 02:44:44, Denys Vlasenko wrote:
> > > > In GDBs case, GDB will want to poke at memory
> > > > right after attaching
> > > 
> > > ...where "right after attaching" is defined as "when the first ptrace-stop
> > > is reported". Which will happen very soon.
> > 
> > Hmm?  Why would it happen very soon?
> > Isn't the point of SEIZE not 
> > interrupting that you'd not get any INTERRUPT or stop at all?
> > Where is the ptrace-stop coming from?
> 
> From PTRACE_INTERRUPT. Without it, tracee is running. 

> Ptrace API never allowed poking of running tracees.

Which is a bit lame.

> You need to stop it first.

That was my point...  I was just pointing out that GDB will end
up PTRACE_INTERRUPTing the target anyway.  Maybe we could extend
GDB's "observer" mode to be even more observer-only, and delay
reading the DSO list and whatever else GDB does on attach until
the first stop, or to user request.  Some archs need reading
registers as soon as possible in order to actually know which
arch variant we've attached to.  Anyway, this is GDBs business.
SEIZE not interrupting won't hurt GDB, and is obviously useful for
some use cases and tracers, _provided the race with SETOPTS is fixed_.

-- 
Pedro Alves

  reply	other threads:[~2011-05-20  8:56 UTC|newest]

Thread overview: 88+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-05-16 18:17 [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and group stop notification, take#2 Tejun Heo
2011-05-16 18:17 ` [PATCH 01/10] signal: remove three noop tracehooks Tejun Heo
2011-05-17 16:22   ` Christoph Hellwig
2011-05-17 16:27     ` Tejun Heo
2011-05-18 18:45   ` Oleg Nesterov
2011-05-19 12:11     ` Tejun Heo
2011-05-19 16:10       ` Oleg Nesterov
2011-05-16 18:17 ` [PATCH 02/10] job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap Tejun Heo
2011-05-18 16:48   ` Oleg Nesterov
2011-05-18 16:57     ` Oleg Nesterov
2011-05-19 10:19     ` Tejun Heo
2011-05-19 16:19       ` Oleg Nesterov
2011-05-16 18:17 ` [PATCH 03/10] ptrace: implement PTRACE_SEIZE Tejun Heo
2011-05-18  0:40   ` Denys Vlasenko
2011-05-18  9:55     ` Tejun Heo
2011-05-18 10:44       ` Denys Vlasenko
2011-05-18 11:14         ` Tejun Heo
2011-05-19 14:17       ` Tejun Heo
2011-05-19 15:02         ` Tejun Heo
2011-05-19 19:31         ` Pedro Alves
2011-05-19 22:42           ` Denys Vlasenko
2011-05-19 23:00             ` Pedro Alves
2011-05-20  1:44               ` Denys Vlasenko
2011-05-20  8:56                 ` Pedro Alves [this message]
2011-05-20  9:12                   ` Tejun Heo
2011-05-20  9:07               ` Tejun Heo
2011-05-20  9:27                 ` Pedro Alves
2011-05-20  9:31                   ` Tejun Heo
2011-05-24  9:49                     ` Pedro Alves
2011-05-24 12:00                       ` Tejun Heo
2011-05-24 12:36                         ` Pedro Alves
2011-05-24 14:02                           ` Tejun Heo
2011-05-24 14:55                             ` Pedro Alves
2011-05-25 18:18                             ` Oleg Nesterov
2011-05-26  9:10                               ` Tejun Heo
2011-05-26 10:01                                 ` Pedro Alves
2011-05-26 10:11                                   ` Tejun Heo
2011-05-26 14:55                                 ` Oleg Nesterov
2011-05-23 13:09         ` Oleg Nesterov
2011-05-23 12:43       ` Oleg Nesterov
2011-05-24 10:28         ` Tejun Heo
2011-05-25 18:29           ` Oleg Nesterov
2011-05-26  9:14             ` Tejun Heo
2011-05-26 15:01               ` Oleg Nesterov
2011-05-27 18:21                 ` Tejun Heo
2011-05-30 19:22                   ` Oleg Nesterov
     [not found]                     ` <BANLkTimupSd774N-VBoswOj+Dza=5ofvWQ@mail.gmail.com>
2011-05-31 19:08                       ` Oleg Nesterov
2011-05-31 21:32                         ` Linus Torvalds
2011-06-01 20:04                           ` Oleg Nesterov
2011-06-01  5:34                         ` Tejun Heo
2011-06-01 20:08                           ` Oleg Nesterov
2011-06-02  5:01                             ` Tejun Heo
2011-05-18 18:17   ` Oleg Nesterov
2011-05-19 10:34     ` Tejun Heo
2011-05-16 18:17 ` [PATCH 04/10] ptrace: implement PTRACE_INTERRUPT Tejun Heo
2011-05-18 18:38   ` Oleg Nesterov
2011-05-19 12:07     ` Tejun Heo
2011-05-19 16:21       ` Oleg Nesterov
2011-05-16 18:17 ` [PATCH 05/10] ptrace: restructure ptrace_getsiginfo() Tejun Heo
2011-05-16 18:17 ` [PATCH 06/10] ptrace: add siginfo.si_pt_flags Tejun Heo
2011-05-16 18:17 ` [PATCH 07/10] ptrace: make group stop state visible via PTRACE_GETSIGINFO Tejun Heo
2011-05-19 16:27   ` Oleg Nesterov
2011-05-19 16:40     ` Tejun Heo
2011-05-16 18:17 ` [PATCH 08/10] ptrace: don't let PTRACE_SETSIGINFO override __SI_TRAP siginfo Tejun Heo
2011-05-16 18:17 ` [PATCH 09/10] ptrace: add JOBCTL_BLOCK_NOTIFY Tejun Heo
2011-05-19 16:32   ` Oleg Nesterov
2011-05-19 16:44     ` Tejun Heo
2011-05-19 16:48       ` Oleg Nesterov
2011-05-19 16:58         ` Tejun Heo
2011-05-16 18:17 ` [PATCH 10/10] ptrace: implement group stop notification for ptracer Tejun Heo
2011-05-19 16:32   ` Oleg Nesterov
2011-05-19 16:57     ` Tejun Heo
2011-05-19 17:13       ` Oleg Nesterov
2011-05-19 22:48         ` Denys Vlasenko
2011-05-20  8:59           ` Tejun Heo
2011-05-23 13:34             ` Oleg Nesterov
2011-05-20  8:46         ` Tejun Heo
2011-05-19 16:58     ` Oleg Nesterov
2011-05-23 11:45       ` Oleg Nesterov
2011-05-24 13:44         ` Tejun Heo
2011-05-24 15:44           ` Tejun Heo
2011-05-26 14:44           ` Oleg Nesterov
2011-05-28  7:32             ` Tejun Heo
2011-05-18 18:50 ` [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and group stop notification, take#2 Oleg Nesterov
2011-05-19 12:08   ` Tejun Heo
2011-05-19 15:04 ` Linus Torvalds
2011-05-19 15:19   ` Tejun Heo
2011-05-19 22:45   ` Denys Vlasenko

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