LKML Archive on
help / color / mirror / Atom feed
From: Oleg Nesterov <>
To: Jan Kiszka <>
Cc: Roland McGrath <>,
	Linux Kernel Mailing List <>
Subject: Re: SIGTRAP vs. sys_exit_group race
Date: Thu, 16 Oct 2008 18:57:27 +0200	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

Roland, what do you think?

On 10/06, Jan Kiszka wrote:
> --- a/kernel/signal.c
> +++ b/kernel/signal.c
> @@ -1528,10 +1528,11 @@ static void ptrace_stop(int exit_code, i
>  		spin_unlock_irq(&current->sighand->siglock);
>  		arch_ptrace_stop(exit_code, info);
>  		spin_lock_irq(&current->sighand->siglock);
> -		if (sigkill_pending(current))
> -			return;
>  	}
> +	if (sigkill_pending(current))
> +		return;
> +

Personally, I think this change is good anyway. The tracee shouldn't
sleep in TASK_TRACED with the pending SIGKILL.

And the current code is confusing, imho. Why do we check sigkill_pending()
under arch_ptrace_stop_needed() ? Yes, it unlocks ->siglock and can sleep,
so SIGKILL can come in between. But it is quite possible that SIGKILL is
already pending when we enter ptrace_stop().

The only problem I can see this patch adds a user-visible change, even
if this change looks good to me. For example, if we send SIGKILL to
the thread group, the tracee will not send PTRACE_EVENT_EXIT.

I think we need further changes. If the thread group group was killed
by some fatal signal (but not SIGKILL) the tracee will sleep with
SIGNAL_GROUP_EXIT, this is not nice too. But imho the patch makes
sense anyway.


  reply	other threads:[~2008-10-16 16:56 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-06 14:08 Jan Kiszka
2008-10-16 16:57 ` Oleg Nesterov [this message]
2008-12-03  4:47   ` Roland McGrath
2008-12-04 18:24     ` 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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \
    --subject='Re: SIGTRAP vs. sys_exit_group race' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

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).