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From:   Linus Torvalds <torvalds@linux-foundation.org>
Date:   Tue, 17 Jul 2018 09:38:44 -0700
Message-ID: <CA+55aFx5gP+1coJ92v4jYgTVfatnOoN3mqrerPEGxadZE2rKNg@mail.gmail.com>
Subject: Re: [RFC][PATCH 07/11] signal: Deliver group signals via PIDTYPE_TGID
 not PIDTYPE_PID
To:     "Eric W. Biederman" <ebiederm@xmission.com>
Cc:     Oleg Nesterov <oleg@redhat.com>,
        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>
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On Mon, Jul 16, 2018 at 7:50 AM Eric W. Biederman <ebiederm@xmission.com> wrote:
>
> In practice since glibc does not make thread id's available I don't
> expect anyone relies on this behavior.  Since no one relies on it we
> can change it without creating a regression.

Actually, there's a really obvious case where this simply isn't true.

Just imagine you're a MIS person or a developer, doing "ps -eLf" to
see what's going on, and want to kill one thread. Either because you
see that one thread using all CPU, or because you are the developer
and you know what's up.

Those thread ID's are exported trivially.

               Linus