Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Tue, 17 Jul 2018 11:56:28 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Wen Yang <wen.yang99@zte.com.cn>, majiang <ma.jiang@zte.com.cn>
Subject: Re: [RFC][PATCH 07/11] signal: Deliver group signals via
 PIDTYPE_TGID not PIDTYPE_PID
Message-ID: <20180717095628.GA27482@redhat.com>
References: <877em2jxyr.fsf_-_@xmission.com>
 <20180711024459.10654-7-ebiederm@xmission.com>
 <20180716125144.GA18262@redhat.com>
 <8736wjtetv.fsf@xmission.com>
 <CA+55aFxDsE8sb5wQQNJdxvt8m6n6aVpOo1yVpk1BEzXDv8XzaQ@mail.gmail.com>
 <87bmb7oy94.fsf@xmission.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <87bmb7oy94.fsf@xmission.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 07/16, Eric W. Biederman wrote:
>
> There are two questions.
> a) Can we use the pid of a thread to find the thread group?
> b) Will the signal be queued in the thread group?

IMO "yes" to both questions, I simply see no reason to change the current
semantics. Even if glibc doesn't show the tread id's a user can see them
in /proc/$tgid/task/. So I think kill_pid_info() should just do

	p = pid_task(pid, PIDTYPE_PID);
	group_send_sig_info(p, PIDTYPE_TGID);

again, posix_timer_event() looks fine, but to me

	pid_task(timr->it_pid, shared ? PIDTYPE_TGID : PIDTYPE_PID)

looks like unnecessary complication,

	pid_task(timr->it_pid, PIDTYPE_PID);

should do the same thing.

And, I didn't mention this yesterday, but probably the next 08/11 patch can
have the same problem. But this is a bit more complicated because send_sigio()
uses the same "type" both for do_each_pid_task() and as an argument passed to
do_send_sig_info().

Oleg.