From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qt0-f199.google.com (mail-qt0-f199.google.com [209.85.216.199]) by kanga.kvack.org (Postfix) with ESMTP id 2B9936B0038 for ; Tue, 4 Oct 2016 12:22:28 -0400 (EDT) Received: by mail-qt0-f199.google.com with SMTP id m9so198414038qte.1 for ; Tue, 04 Oct 2016 09:22:28 -0700 (PDT) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id q62si3198848qka.114.2016.10.04.09.22.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 04 Oct 2016 09:22:27 -0700 (PDT) Date: Tue, 4 Oct 2016 18:21:14 +0200 From: Oleg Nesterov Subject: Re: [PATCH 3/4] mm, oom: do not rely on TIF_MEMDIE for exit_oom_victim Message-ID: <20161004162114.GB32428@redhat.com> References: <20161004090009.7974-1-mhocko@kernel.org> <20161004090009.7974-4-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161004090009.7974-4-mhocko@kernel.org> Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, David Rientjes , Tetsuo Handa , Johannes Weiner , Andrew Morton , LKML , Michal Hocko , Al Viro On 10/04, Michal Hocko wrote: > > -void release_task(struct task_struct *p) > +bool release_task(struct task_struct *p) > { > struct task_struct *leader; > int zap_leader; > + bool last = false; > repeat: > /* don't need to get the RCU readlock here - the process is dead and > * can't be modifying its own credentials. But shut RCU-lockdep up */ > @@ -197,8 +198,10 @@ void release_task(struct task_struct *p) > * then we are the one who should release the leader. > */ > zap_leader = do_notify_parent(leader, leader->exit_signal); > - if (zap_leader) > + if (zap_leader) { > leader->exit_state = EXIT_DEAD; > + last = true; > + } > } This looks strange... it won't return true if "p" is the group leader. > @@ -584,12 +587,15 @@ static void forget_original_parent(struct task_struct *father, > /* > * Send signals to all our closest relatives so that they know > * to properly mourn us.. > + * > + * Returns true if this is the last thread from the thread group > */ > -static void exit_notify(struct task_struct *tsk, int group_dead) > +static bool exit_notify(struct task_struct *tsk, int group_dead) > { > bool autoreap; > struct task_struct *p, *n; > LIST_HEAD(dead); > + bool last = false; > > write_lock_irq(&tasklist_lock); > forget_original_parent(tsk, &dead); > @@ -606,6 +612,7 @@ static void exit_notify(struct task_struct *tsk, int group_dead) > } else if (thread_group_leader(tsk)) { > autoreap = thread_group_empty(tsk) && > do_notify_parent(tsk, tsk->exit_signal); > + last = thread_group_empty(tsk); so this can't detect the multi-threaded group exit, and ... > list_for_each_entry_safe(p, n, &dead, ptrace_entry) { > list_del_init(&p->ptrace_entry); > - release_task(p); > + if (release_task(p) && p == tsk) > + last = true; this can only happen if this process auto-reaps itself. Not to mention that exit_notify() will never return true if traced. No, this doesn't look right. Oleg. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754180AbcJDQW2 (ORCPT ); Tue, 4 Oct 2016 12:22:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:53770 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754021AbcJDQW1 (ORCPT ); Tue, 4 Oct 2016 12:22:27 -0400 Date: Tue, 4 Oct 2016 18:21:14 +0200 From: Oleg Nesterov To: Michal Hocko Cc: linux-mm@kvack.org, David Rientjes , Tetsuo Handa , Johannes Weiner , Andrew Morton , LKML , Michal Hocko , Al Viro Subject: Re: [PATCH 3/4] mm, oom: do not rely on TIF_MEMDIE for exit_oom_victim Message-ID: <20161004162114.GB32428@redhat.com> References: <20161004090009.7974-1-mhocko@kernel.org> <20161004090009.7974-4-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161004090009.7974-4-mhocko@kernel.org> User-Agent: Mutt/1.5.18 (2008-05-17) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.26]); Tue, 04 Oct 2016 16:22:26 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/04, Michal Hocko wrote: > > -void release_task(struct task_struct *p) > +bool release_task(struct task_struct *p) > { > struct task_struct *leader; > int zap_leader; > + bool last = false; > repeat: > /* don't need to get the RCU readlock here - the process is dead and > * can't be modifying its own credentials. But shut RCU-lockdep up */ > @@ -197,8 +198,10 @@ void release_task(struct task_struct *p) > * then we are the one who should release the leader. > */ > zap_leader = do_notify_parent(leader, leader->exit_signal); > - if (zap_leader) > + if (zap_leader) { > leader->exit_state = EXIT_DEAD; > + last = true; > + } > } This looks strange... it won't return true if "p" is the group leader. > @@ -584,12 +587,15 @@ static void forget_original_parent(struct task_struct *father, > /* > * Send signals to all our closest relatives so that they know > * to properly mourn us.. > + * > + * Returns true if this is the last thread from the thread group > */ > -static void exit_notify(struct task_struct *tsk, int group_dead) > +static bool exit_notify(struct task_struct *tsk, int group_dead) > { > bool autoreap; > struct task_struct *p, *n; > LIST_HEAD(dead); > + bool last = false; > > write_lock_irq(&tasklist_lock); > forget_original_parent(tsk, &dead); > @@ -606,6 +612,7 @@ static void exit_notify(struct task_struct *tsk, int group_dead) > } else if (thread_group_leader(tsk)) { > autoreap = thread_group_empty(tsk) && > do_notify_parent(tsk, tsk->exit_signal); > + last = thread_group_empty(tsk); so this can't detect the multi-threaded group exit, and ... > list_for_each_entry_safe(p, n, &dead, ptrace_entry) { > list_del_init(&p->ptrace_entry); > - release_task(p); > + if (release_task(p) && p == tsk) > + last = true; this can only happen if this process auto-reaps itself. Not to mention that exit_notify() will never return true if traced. No, this doesn't look right. Oleg.