Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Mon, 22 Jun 2020 15:01:55 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Christian Brauner <christian.brauner@ubuntu.com>
Cc:     Dominique Martinet <asmadeus@codewreck.org>,
        Alexander Kapshuk <alexander.kapshuk@gmail.com>,
        linux-kernel@vger.kernel.org, ebiederm@xmission.com,
        akpm@linux-foundation.org, liuzhiqiang26@huawei.com,
        joel@joelfernandes.org, paulmck@linux.vnet.ibm.com,
        kernel test robot <lkp@intel.com>
Subject: Re: [PATCH] kernel/signal.c: Export symbol __lock_task_sighand
Message-ID: <20200622130155.GE6516@redhat.com>
References: <20200621133704.77896-1-alexander.kapshuk@gmail.com>
 <20200622062527.GA6516@redhat.com>
 <20200622083905.c3nurmkbo5yhd6lj@wittgenstein>
 <20200622102401.GA12377@nautica>
 <20200622113610.okzntx7jmnk6n7au@wittgenstein>
 <20200622120259.GD6516@redhat.com>
 <20200622122925.khcilncycuzb4xki@wittgenstein>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20200622122925.khcilncycuzb4xki@wittgenstein>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On 06/22, Christian Brauner wrote:
>
> It is a supported case however unlikely. I just tried to answer
> Dominique's specific question pointing out that even in that unlikely
> case sighand_struct is stable.

I too tried to say this, but apparently just added more confusion ;)

> Just as an fyi, CLONE_SIGHAND with CLONE_VM but without CLONE_THREAD is
> actually used quite a bit, e.g. in newlib, in stress-ng, and in criu.

OK,

> you'd want CLONE_VM which enforces
> CLONE_SIGHAND so that would be another use-case afaict.

Cough no ;) CLONE_SIGHAND requires CLONE_VM, not vice versa.

> > But this doesn't really matter. I mean, even if you race with another
> > thread doing exec/exit/whatever, current->sighand is stable. Unless, again,
> > current has already exited (called exit_notify()).

Oleg.