From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47415C433DF for ; Thu, 2 Jul 2020 16:48:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 30DA620720 for ; Thu, 2 Jul 2020 16:48:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727798AbgGBQsl (ORCPT ); Thu, 2 Jul 2020 12:48:41 -0400 Received: from out03.mta.xmission.com ([166.70.13.233]:40794 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727120AbgGBQsi (ORCPT ); Thu, 2 Jul 2020 12:48:38 -0400 Received: from in01.mta.xmission.com ([166.70.13.51]) by out03.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jr2O5-000260-NZ; Thu, 02 Jul 2020 10:48:37 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.int.ebiederm.org) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1jr2Nl-0007up-A6; Thu, 02 Jul 2020 10:48:18 -0600 From: "Eric W. Biederman" To: linux-kernel@vger.kernel.org Cc: David Miller , Greg Kroah-Hartman , Tetsuo Handa , Alexei Starovoitov , Kees Cook , Andrew Morton , Alexei Starovoitov , Al Viro , bpf , linux-fsdevel , Daniel Borkmann , Jakub Kicinski , Masahiro Yamada , Gary Lin , Bruno Meneguele , LSM List , Casey Schaufler , Luis Chamberlain , Linus Torvalds , Christian Brauner , "Eric W. Biederman" Date: Thu, 2 Jul 2020 11:41:37 -0500 Message-Id: <20200702164140.4468-13-ebiederm@xmission.com> X-Mailer: git-send-email 2.25.0 In-Reply-To: <87y2o1swee.fsf_-_@x220.int.ebiederm.org> References: <87y2o1swee.fsf_-_@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-XM-SPF: eid=1jr2Nl-0007up-A6;;;mid=<20200702164140.4468-13-ebiederm@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19HmRhPZpVcthqXrkTnKi3I8QVAgMh9DzI= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH v3 13/16] exit: Factor thread_group_exited out of pidfd_poll X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Create an independent helper thread_group_exited report return true when all threads have passed exit_notify in do_exit. AKA all of the threads are at least zombies and might be dead or completely gone. Create this helper by taking the logic out of pidfd_poll where it is already tested, and adding a missing READ_ONCE on the read of task->exit_state. I will be changing the user mode driver code to use this same logic to know when a user mode driver needs to be restarted. Place the new helper thread_group_exited in kernel/exit.c and EXPORT it so it can be used by modules. Signed-off-by: "Eric W. Biederman" --- include/linux/sched/signal.h | 2 ++ kernel/exit.c | 24 ++++++++++++++++++++++++ kernel/fork.c | 6 +----- 3 files changed, 27 insertions(+), 5 deletions(-) diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index 0ee5e696c5d8..1bad18a1d8ba 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -674,6 +674,8 @@ static inline int thread_group_empty(struct task_struct *p) #define delay_group_leader(p) \ (thread_group_leader(p) && !thread_group_empty(p)) +extern bool thread_group_exited(struct pid *pid); + extern struct sighand_struct *__lock_task_sighand(struct task_struct *task, unsigned long *flags); diff --git a/kernel/exit.c b/kernel/exit.c index d3294b611df1..a7f112feb0f6 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1713,6 +1713,30 @@ COMPAT_SYSCALL_DEFINE5(waitid, } #endif +/** + * thread_group_exited - check that a thread group has exited + * @pid: tgid of thread group to be checked. + * + * Test if thread group is has exited (all threads are zombies, dead + * or completely gone). + * + * Return: true if the thread group has exited. false otherwise. + */ +bool thread_group_exited(struct pid *pid) +{ + struct task_struct *task; + bool exited; + + rcu_read_lock(); + task = pid_task(pid, PIDTYPE_PID); + exited = !task || + (READ_ONCE(task->exit_state) && thread_group_empty(task)); + rcu_read_unlock(); + + return exited; +} +EXPORT_SYMBOL(thread_group_exited); + __weak void abort(void) { BUG(); diff --git a/kernel/fork.c b/kernel/fork.c index 142b23645d82..bf215af7a904 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1787,22 +1787,18 @@ static void pidfd_show_fdinfo(struct seq_file *m, struct file *f) */ static __poll_t pidfd_poll(struct file *file, struct poll_table_struct *pts) { - struct task_struct *task; struct pid *pid = file->private_data; __poll_t poll_flags = 0; poll_wait(file, &pid->wait_pidfd, pts); - rcu_read_lock(); - task = pid_task(pid, PIDTYPE_PID); /* * Inform pollers only when the whole thread group exits. * If the thread group leader exits before all other threads in the * group, then poll(2) should block, similar to the wait(2) family. */ - if (!task || (task->exit_state && thread_group_empty(task))) + if (thread_group_exited(pid)) poll_flags = EPOLLIN | EPOLLRDNORM; - rcu_read_unlock(); return poll_flags; } -- 2.25.0