From: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Pedro Alves <palves-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Mike Frysinger <vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org>,
"Michael Kerrisk (man-pages)"
<mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
pacman-ptgZXYu0fikgsBAKwltoeQ@public.gmane.org,
linux-man <linux-man-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
lkml <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Denys Vlasenko <dvlasenk-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
Jan Kratochvil
<jan.kratochvil-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Subject: Re: ptrace.2: PTRACE_KILL needs a stopped process too
Date: Wed, 9 May 2012 22:12:19 +0200 [thread overview]
Message-ID: <20120509201219.GA32051@redhat.com> (raw)
In-Reply-To: <4FAAC706.6000808-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
On 05/09, Pedro Alves wrote:
>
> On 05/09/2012 04:09 PM, Mike Frysinger wrote:
>
> > probably not that big of a deal, but the reason i like using
> > ptrace(PTRACE_KILL) over a raw kill() is that you are less likely to kill the
> > wrong process by accident. maybe not that big of a deal in practice though.
>
>
> And you can do tgkill instead. It was specifically invented to handle the
> reuse case.
tgkill() can kill the wrong process/thread too, although it lessens the risk.
But I don't really understand the problem. The traced thread can't go away
until the tracer does wait/detach, and thus its pid can't be reused?
May be, "by accident" above means something else, not pid reuse...
Oleg.
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WARNING: multiple messages have this Message-ID (diff)
From: Oleg Nesterov <oleg@redhat.com>
To: Pedro Alves <palves@redhat.com>
Cc: Mike Frysinger <vapier@gentoo.org>,
"Michael Kerrisk (man-pages)" <mtk.manpages@gmail.com>,
pacman@kosh.dhis.org, linux-man <linux-man@vger.kernel.org>,
lkml <linux-kernel@vger.kernel.org>,
Denys Vlasenko <dvlasenk@redhat.com>, Tejun Heo <tj@kernel.org>,
Jan Kratochvil <jan.kratochvil@redhat.com>
Subject: Re: ptrace.2: PTRACE_KILL needs a stopped process too
Date: Wed, 9 May 2012 22:12:19 +0200 [thread overview]
Message-ID: <20120509201219.GA32051@redhat.com> (raw)
In-Reply-To: <4FAAC706.6000808@redhat.com>
On 05/09, Pedro Alves wrote:
>
> On 05/09/2012 04:09 PM, Mike Frysinger wrote:
>
> > probably not that big of a deal, but the reason i like using
> > ptrace(PTRACE_KILL) over a raw kill() is that you are less likely to kill the
> > wrong process by accident. maybe not that big of a deal in practice though.
>
>
> And you can do tgkill instead. It was specifically invented to handle the
> reuse case.
tgkill() can kill the wrong process/thread too, although it lessens the risk.
But I don't really understand the problem. The traced thread can't go away
until the tracer does wait/detach, and thus its pid can't be reused?
May be, "by accident" above means something else, not pid reuse...
Oleg.
next prev parent reply other threads:[~2012-05-09 20:12 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20091216004533.22261.qmail@kosh.dhis.org>
[not found] ` <20091216004533.22261.qmail-ptgZXYu0fikgsBAKwltoeQ@public.gmane.org>
2012-04-22 18:56 ` ptrace.2: PTRACE_KILL needs a stopped process too Michael Kerrisk (man-pages)
2012-04-22 18:56 ` Michael Kerrisk (man-pages)
[not found] ` <CAKgNAkhtu8d0NKcTwWyCA8qWgz8Lag+GcpEE1=YMVe_Nh8XJ9Q-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-04-22 20:04 ` Oleg Nesterov
2012-04-22 20:04 ` Oleg Nesterov
[not found] ` <20120422200459.GA7519-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2012-05-02 12:06 ` Pedro Alves
2012-05-02 12:06 ` Pedro Alves
2012-05-09 15:09 ` Mike Frysinger
2012-05-09 15:09 ` Mike Frysinger
[not found] ` <201205091109.35637.vapier-aBrp7R+bbdUdnm+yROfE0A@public.gmane.org>
2012-05-09 19:35 ` Pedro Alves
2012-05-09 19:35 ` Pedro Alves
[not found] ` <4FAAC706.6000808-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2012-05-09 20:12 ` Oleg Nesterov [this message]
2012-05-09 20:12 ` Oleg Nesterov
[not found] ` <20120509201219.GA32051-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2012-05-09 16:41 ` Mike Frysinger
2012-05-09 16:41 ` Mike Frysinger
2012-05-09 21:14 ` Oleg Nesterov
[not found] ` <20120509211429.GA2455-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
2012-05-09 22:16 ` Pedro Alves
2012-05-09 22:16 ` Pedro Alves
2012-05-09 22:08 ` Pedro Alves
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