From: Tejun Heo <tj@kernel.org>
To: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Oleg Nesterov <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, pedro@codesourcery.com
Subject: Re: [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and group stop notification, take#4
Date: Fri, 3 Jun 2011 10:34:23 +0900 [thread overview]
Message-ID: <20110603013423.GB14872@mtj.dyndns.org> (raw)
In-Reply-To: <201106022309.44663.vda.linux@googlemail.com>
Hello, Oleg, Denys.
On Thu, Jun 02, 2011 at 11:09:44PM +0200, Denys Vlasenko wrote:
> > and signr is roughly calculated as
> >
> > if (group_stop_count || SIGNAL_STOP_STOPPED)
> > signr = jobctl & JOBCTL_STOP_SIGMASK;
> > else if (JOBCTL_TRAP_NOTIFY)
> > signr = SIGCONT;
> > else
> > signr = SIGTRAP; // PTRACE_INTERRUPT
> >
> > In this case we can avoid all siginfo changes. The tracer does wait(status)
> > anyway, it can see the state without GETSIGINFO. The only problem, the tracer
> > should be careful to avoid the confusion with ptrace_signal(), it should
> > check status & (PTRACE_EVENT_STOP << 16).
> >
> > What do you think?
Yeap, it makes sense.
> This should alleviate Linus' concerns that we are suffering from unnecessary
> featuritis - that we invent API which is significantly different
> from existing one, and as such users will not use it.
>
> Existing API doesn't use GETSIGINFO data per se to distinguish group-stop from
> signal-delivery-stop, it uses the fact that GETSIGINFO fails on group-stop.
> (Well, arguably it's not a "designed" API, more like "accidentally created API",
> but nevertheless it exists right now). Oleg's proposal means that the new way
> may be makde to work very similarly.
Okay, you want to preserve %NULL SIGINFO on all STOP traps. Dropping
si_pt_flags and using exit_code makes sense but I think we'll be
better off enabling GETSIGINFO. The affected part of code has to be
changed anyway and with %NULL GETSIGINFO we effectively would have
driven ourselves into corner if more information needs to be added
later on. Don't current users unconditionally issue CONT(sig) anyway?
> The less we deverge in handling of group-stop from existing API while fixing it,
> the better. If the only thing strace needs to change is to issue PTRACE_LISTEN
> instead of PTRACE_CONT on group-stop, then it's wonderful.
>
> I understand that this patchset doesn't do exactly that yet, but it appears
> it can be achieved relatively easy by a future change. Don't take this
> as a request to respin the patchset yet again.
Heh, don't worry about re-spinning. It's only take#4 now after all. :)
Thanks.
--
tejun
next prev parent reply other threads:[~2011-06-03 1:34 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-29 23:12 [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and group stop notification, take#4 Tejun Heo
2011-05-29 23:12 ` [PATCH 01/17] ptrace: remove silly wait_trap variable from ptrace_attach() Tejun Heo
2011-06-01 18:47 ` Oleg Nesterov
2011-06-02 5:03 ` Tejun Heo
2011-06-02 11:39 ` [PATCH UPDATED " Tejun Heo
2011-05-29 23:12 ` [PATCH 02/17] job control: rename signal->group_stop and flags to jobctl and update them Tejun Heo
2011-05-29 23:12 ` [PATCH 03/17] ptrace: ptrace_check_attach(): rename @kill to @ignore_state and add comments Tejun Heo
2011-05-29 23:12 ` [PATCH 04/17] ptrace: relocate set_current_state(TASK_TRACED) in ptrace_stop() Tejun Heo
2011-05-29 23:12 ` [PATCH 05/17] job control: introduce JOBCTL_PENDING_MASK and task_clear_jobctl_pending() Tejun Heo
2011-05-29 23:12 ` [PATCH 06/17] job control: make task_clear_jobctl_pending() clear TRAPPING automatically Tejun Heo
2011-05-29 23:12 ` [PATCH 07/17] job control: introduce task_set_jobctl_pending() Tejun Heo
2011-05-29 23:12 ` [PATCH 08/17] ptrace: use bit_waitqueue for TRAPPING instead of wait_chldexit Tejun Heo
2011-06-02 11:41 ` [PATCH UPDATED " Tejun Heo
2011-05-29 23:12 ` [PATCH 09/17] signal: remove three noop tracehooks Tejun Heo
2011-05-29 23:12 ` [PATCH 10/17] job control: introduce JOBCTL_TRAP_STOP and use it for group stop trap Tejun Heo
2011-05-29 23:12 ` [PATCH 11/17] ptrace: implement PTRACE_SEIZE Tejun Heo
2011-06-01 19:01 ` Oleg Nesterov
2011-06-01 19:55 ` Oleg Nesterov
2011-06-02 5:13 ` Tejun Heo
2011-06-02 11:43 ` [PATCH UPDATED " Tejun Heo
2011-05-29 23:12 ` [PATCH 12/17] ptrace: implement PTRACE_INTERRUPT Tejun Heo
2011-05-29 23:12 ` [PATCH 13/17] ptrace: add siginfo.si_pt_flags Tejun Heo
2011-05-29 23:12 ` [PATCH 14/17] ptrace: make group stop state visible via PTRACE_GETSIGINFO Tejun Heo
2011-05-29 23:12 ` [PATCH 15/17] ptrace: don't let PTRACE_SETSIGINFO override __SI_TRAP siginfo Tejun Heo
2011-05-29 23:12 ` [PATCH 16/17] ptrace: implement TRAP_NOTIFY and use it for group stop events Tejun Heo
2011-05-29 23:12 ` [PATCH 17/17] ptrace: implement PTRACE_LISTEN Tejun Heo
2011-06-02 17:33 ` Oleg Nesterov
2011-06-13 14:10 ` Tejun Heo
2011-06-13 20:33 ` Oleg Nesterov
2011-06-14 6:45 ` Tejun Heo
2011-05-30 15:42 ` [PATCHSET ptrace] ptrace: implement PTRACE_SEIZE/INTERRUPT and group stop notification, take#4 Oleg Nesterov
2011-06-01 5:39 ` Tejun Heo
2011-06-02 12:31 ` Tejun Heo
2011-06-02 14:51 ` Denys Vlasenko
2011-06-03 1:24 ` Tejun Heo
2011-06-03 10:25 ` Pedro Alves
2011-06-16 8:38 ` Tejun Heo
2011-06-16 9:56 ` Pedro Alves
2011-06-17 19:08 ` Oleg Nesterov
2011-06-03 11:57 ` Denys Vlasenko
2011-06-03 12:11 ` Pedro Alves
2011-06-03 14:12 ` Denys Vlasenko
2011-06-03 15:24 ` Pedro Alves
2011-06-03 15:46 ` Oleg Nesterov
2011-06-02 18:27 ` Oleg Nesterov
2011-06-02 21:09 ` Denys Vlasenko
2011-06-03 1:34 ` Tejun Heo [this message]
2011-06-03 11:37 ` Denys Vlasenko
2011-06-03 11:58 ` Denys Vlasenko
2011-06-03 15:37 ` Oleg Nesterov
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