From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Subject: Re: [PATCH v4] kernel/signal: Signal-based pre-coredump notification Date: Mon, 29 Oct 2018 12:18:05 +0100 Message-ID: <20181029111804.GA24820@redhat.com> References: <458c04d8-d189-4a26-729a-bb1d1d751534@cisco.com> <7741efa7-a3f8-62a1-ba52-613883164643@cisco.com> <84460a77-a111-404e-4bad-88104a6e246e@cisco.com> <20181026082812.GA10581@redhat.com> <21f678a8-4001-df36-c26e-e96cf203b1b1@cisco.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <21f678a8-4001-df36-c26e-e96cf203b1b1@cisco.com> Sender: linux-kernel-owner@vger.kernel.org To: Enke Chen Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Peter Zijlstra , Arnd Bergmann , "Eric W. Biederman" , Khalid Aziz , Kate Stewart , Helge Deller , Greg Kroah-Hartman , Al Viro , Andrew Morton , Christian Brauner , Catalin Marinas , Will Deacon , Dave Martin , Mauro Carvalho Chehab , Michal Hocko , Rik van Riel List-Id: linux-arch.vger.kernel.org Hi, On 10/26, Enke Chen wrote: > > This is really a good idea given that "parent" is declared as RCU-protected. > Just a bit odd, though, that the "parent" has not been accessed this way in > the code base. It is acccessed when possible, > So just to confirm: the revised code would look like the following: > > static void do_notify_parent_predump(void) > { > struct task_struct *parent; > int sig; > > rcu_read_lock(); > parent = rcu_dereference(current->parent); > sig = parent->signal->predump_signal; > if (sig != 0) > do_send_sig_info(sig, SEND_SIG_NOINFO, parent, PIDTYPE_TGID); > rcu_read_unlock(); > } Yes, this is what I meant. But I still think do_notify_parent_predump() should notify ->real_parent, not ->parent. Oleg. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:46392 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726720AbeJ2UGa (ORCPT ); Mon, 29 Oct 2018 16:06:30 -0400 Date: Mon, 29 Oct 2018 12:18:05 +0100 From: Oleg Nesterov Subject: Re: [PATCH v4] kernel/signal: Signal-based pre-coredump notification Message-ID: <20181029111804.GA24820@redhat.com> References: <458c04d8-d189-4a26-729a-bb1d1d751534@cisco.com> <7741efa7-a3f8-62a1-ba52-613883164643@cisco.com> <84460a77-a111-404e-4bad-88104a6e246e@cisco.com> <20181026082812.GA10581@redhat.com> <21f678a8-4001-df36-c26e-e96cf203b1b1@cisco.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <21f678a8-4001-df36-c26e-e96cf203b1b1@cisco.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Enke Chen Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , Peter Zijlstra , Arnd Bergmann , "Eric W. Biederman" , Khalid Aziz , Kate Stewart , Helge Deller , Greg Kroah-Hartman , Al Viro , Andrew Morton , Christian Brauner , Catalin Marinas , Will Deacon , Dave Martin , Mauro Carvalho Chehab , Michal Hocko , Rik van Riel , "Kirill A. Shutemov" , Roman Gushchin , Marcos Paulo de Souza , Dominik Brodowski , Cyrill Gorcunov , Yang Shi , Jann Horn , Kees Cook , x86@kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, "Victor Kamensky (kamensky)" , xe-linux-external@cisco.com, Stefan Strogin Message-ID: <20181029111805.3ORVwxl9H7eoiDyTEqRWadVIMVwrTJx9cc7eAlqTYUE@z> Hi, On 10/26, Enke Chen wrote: > > This is really a good idea given that "parent" is declared as RCU-protected. > Just a bit odd, though, that the "parent" has not been accessed this way in > the code base. It is acccessed when possible, > So just to confirm: the revised code would look like the following: > > static void do_notify_parent_predump(void) > { > struct task_struct *parent; > int sig; > > rcu_read_lock(); > parent = rcu_dereference(current->parent); > sig = parent->signal->predump_signal; > if (sig != 0) > do_send_sig_info(sig, SEND_SIG_NOINFO, parent, PIDTYPE_TGID); > rcu_read_unlock(); > } Yes, this is what I meant. But I still think do_notify_parent_predump() should notify ->real_parent, not ->parent. Oleg.