From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [PATCH v2] prctl: add PR_[GS]ET_KILLABLE Date: Wed, 1 Aug 2018 16:19:15 +0200 Message-ID: <20180801141914.GA21248@redhat.com> References: <20180730075241.24002-1-j@bitron.ch> <20180731070337.61004-1-j@bitron.ch> <20180731143949.GA1890@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: =?iso-8859-1?Q?J=FCrg?= Billeter Cc: Andrew Morton , Thomas Gleixner , Eric Biederman , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-api@vger.kernel.org On 07/31, Jürg Billeter wrote: > > > Could you explain your use-case? Why a shell wants to use > > CLONE_NEWPID? > > To guarantee that there won't be any runaway processes, i.e., ensure > that no descendants (background helper daemons or misbehaving > processes) survive when the child process is terminated. We already have PR_SET_CHILD_SUBREAPER. Perhaps we can finally add PR_KILL_MY_DESCENDANTS_ON_EXIT? This was already discussed some time ago, but I can't find the previous discussion... Simple to implement. > And to prevent > children from killing their ancestors. OK, this is the only reason for CLONE_NEWPID which I can understand so far. Not that I understand why this is that useful ;) > > > * As SIGSTOP is ignored when raised from the SIGNAL_UNKILLABLE process > > > itself, it's not possible to implement the stop action in a custom > > > SIGTSTP handler. > > > > Yes. So may be we actually want to change __isig() paths to use > > SEND_SIG_FORCED (this is not that simple), or perhaps we can change > > __send_signal() to not drop SIGSTOP sent to itself, or may be we can even > > introduce SIG_DFL_EVEN_IF_INIT, I dunno. > > In my opinion, my patch is much simpler and also more general as it Yes, yes, let me repeat that I am not arguing with your patch, I am just trying to understand what > > I can't understand this. An application should be changed anyway to do > > PR_SET_KILLABLE? > > PR_SET_KILLABLE can be called (e.g., by the shell) between clone() and > execve(). OK, this is true. Oleg.