From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?J=FCrg?= Billeter Subject: Re: [PATCH] prctl: add PR_{GET,SET}_KILL_DESCENDANTS_ON_EXIT Date: Thu, 29 Nov 2018 15:41:38 +0000 Message-ID: References: <20181127225408.7553-1-j@bitron.ch> <20181127225408.7553-2-j@bitron.ch> <20181128144230.GG30395@redhat.com> <87r2f5gr9g.fsf@xmission.com> <20181129123409.GA10645@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20181129123409.GA10645@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Oleg Nesterov , "Eric W. Biederman" Cc: Andrew Morton , Thomas Gleixner , Kees Cook , Andy Lutomirski , linux-api@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-api@vger.kernel.org Hi Oleg, Thanks for the review. On Thu, 2018-11-29 at 13:34 +0100, Oleg Nesterov wrote: > To me it would be more clean to call walk_process_tree(kill_descendant_visitor) > unconditionally in find_new_reaper() right before "if (has_child_subreaper)", but > then we will need to shift read_lock(tasklist) from walk_process_tree(). Yes, that's the reason why I added the call before the tasklist lock. Let me know if you want me to move the read lock from walk_process_tree() to PR_SET_CHILD_SUBREAPER (the only caller) instead. > So I think the patch is mostly fine, the only problem I can see is that > PR_SET_KILL_DESCENDANTS_ON_EXIT can race with PR_SET_CHILD_SUBREAPER, they both > need to update the bits in the same word. Good point. I'll make it a regular bool instead of a bitfield for v2, unless you have another approach in mind to fix this. Jürg