From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: vda.linux@googlemail.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: [PATCH 17/17] ptrace: implement PTRACE_LISTEN
Date: Mon, 13 Jun 2011 22:33:41 +0200 [thread overview]
Message-ID: <20110613203341.GA15695@redhat.com> (raw)
In-Reply-To: <20110613141023.GA8141@htj.dyndns.org>
Hello Tejun,
On 06/13, Tejun Heo wrote:
>
> On Thu, Jun 02, 2011 at 07:33:30PM +0200, Oleg Nesterov wrote:
> > > + /*
> > > + * If NOTIFY is set, it means event happened between start
> > > + * of this trap and now. Trigger re-trap immediately.
> > > + */
> > > + if (child->jobctl & JOBCTL_TRAP_NOTIFY)
> > > + signal_wake_up(child, true);
> >
> > Again, I won't insist if you prefer signal_wake_up(), but afaics
> > wake_up_state(__TASK_TRACED) should be enough.
>
> Re-trapping from attach/detach paths are already using
> signal_wake_up()
because attach sets TRAP_STOP which contributes to recalc_sigpending().
If JOBCTL_TRAP_NOTIFY is set, TIF_SIGPENDING should be already set as
well by the same reason. And in any case ptrace_stop() does
recalc_sigpending_tsk() before return, TIF_SIGPENDING is never really
needed when we are going to wake up the TASK_TRACED task.
However,
> and I think it would be better to keep it consistent.
OK, I don't really mind, up to you.
> > OK. The only thing I can't understand is why prepare_signal(SIGCONT)
> > calls ptrace_trap_notify() unconditionally. How about
> >
> > if (likely(!(t->ptrace & PT_SEIZED)))
> > wake_up_state(t, __TASK_STOPPED);
> > - else
> > + else if (why)
> > ptrace_trap_notify(t);
> >
> > ?
>
> I'm having a Deja Vu.
Me too...
> Did I reply to this already? Anyways, here are
> my rationales.
>
> * Tracer should be able to handle seemingly spurious notifications.
> ...
> SIGCONT always generating notification is correct
Yes, I didn't say this is wrong.
> and I don't see
> good reasons to optimize it. Moreover, I think it doesn't hurt to
> have a way to reliably trigger spurious notification.
Well. I don't really understand why, but OK. Let's keep it this way.
> * If we're gonna optimize out SIGCONT processing if the target process
> doesn't need it, the proper way would be testing stopped state and
> exit before walking through the group list.
We can't, at least we need rm_from_queue(SIG_KERNEL_STOP_MASK) and
task_clear_jobctl_pending().
> However, I think it's
> done the current way for a reason - always trying to wake up on
> SIGCONT is more robust in case something went out of sync
Hmm. I am wondering if we can ever see why == 0 && __TASK_STOPPED with
the recent fixes...
> So, I'd like to keep this one as it currently is.
OK.
Oleg.
next prev parent reply other threads:[~2011-06-13 20:35 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 [this message]
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
2011-06-03 11:37 ` Denys Vlasenko
2011-06-03 11:58 ` Denys Vlasenko
2011-06-03 15:37 ` Oleg Nesterov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20110613203341.GA15695@redhat.com \
--to=oleg@redhat.com \
--cc=akpm@linux-foundation.org \
--cc=bdonlan@gmail.com \
--cc=indan@nul.nu \
--cc=jan.kratochvil@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=pedro@codesourcery.com \
--cc=tj@kernel.org \
--cc=torvalds@linux-foundation.org \
--cc=vda.linux@googlemail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).