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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C78DC433F5 for ; Fri, 6 May 2022 14:15:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1442147AbiEFOTa (ORCPT ); Fri, 6 May 2022 10:19:30 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42830 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1442156AbiEFOTW (ORCPT ); Fri, 6 May 2022 10:19:22 -0400 Received: from out03.mta.xmission.com (out03.mta.xmission.com [166.70.13.233]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 24F6024BDB; Fri, 6 May 2022 07:15:39 -0700 (PDT) Received: from in01.mta.xmission.com ([166.70.13.51]:33946) by out03.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1nmyk5-001V1f-P3; Fri, 06 May 2022 08:15:38 -0600 Received: from ip68-227-174-4.om.om.cox.net ([68.227.174.4]:37210 helo=localhost.localdomain) by in01.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1nmyk4-007Cxx-KB; Fri, 06 May 2022 08:15:37 -0600 From: "Eric W. Biederman" To: linux-arch@vger.kernel.org Cc: Tejun Heo , Peter Zijlstra , Vincent Guittot , Al Viro , Jens Axboe , Thomas Gleixner , Linus Torvalds , linux-kernel@vger.kernel.org, "Eric W. Biederman" Date: Fri, 6 May 2022 09:15:08 -0500 Message-Id: <20220506141512.516114-3-ebiederm@xmission.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <87mtfu4up3.fsf@email.froward.int.ebiederm.org> References: <87mtfu4up3.fsf@email.froward.int.ebiederm.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-XM-SPF: eid=1nmyk4-007Cxx-KB;;;mid=<20220506141512.516114-3-ebiederm@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=68.227.174.4;;;frm=ebiederm@xmission.com;;;spf=softfail X-XM-AID: U2FsdGVkX1/mDmv+ns3fcb9e/GMSp2NnY4KNRo/+Yic= X-SA-Exim-Connect-IP: 68.227.174.4 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: [PATCH 3/7] fork: Explicity test for idle tasks in copy_thread X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-arch@vger.kernel.org The architectures ia64 and parisc have special handling for the idle thread in copy_process. Add a flag named idle to kernel_clone_args and use it to explicity test if an idle process is being created. Fullfill the expectations of the rest of the copy_thread implemetations and pass a function pointer in .stack from fork_idle(). This makes what is happening in copy_thread better defined, and is useful to make idle threads less special. Signed-off-by: "Eric W. Biederman" --- arch/ia64/kernel/process.c | 2 +- arch/parisc/kernel/process.c | 2 +- include/linux/sched/task.h | 1 + kernel/fork.c | 9 +++++++++ 4 files changed, 12 insertions(+), 2 deletions(-) diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c index 10d41ded05a5..8f010ae818bc 100644 --- a/arch/ia64/kernel/process.c +++ b/arch/ia64/kernel/process.c @@ -342,7 +342,7 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args) ia64_drop_fpu(p); /* don't pick up stale state from a CPU's fph */ if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) { - if (unlikely(!user_stack_base)) { + if (unlikely(args->idle)) { /* fork_idle() called us */ return 0; } diff --git a/arch/parisc/kernel/process.c b/arch/parisc/kernel/process.c index 129c17de45ba..30a5874ca845 100644 --- a/arch/parisc/kernel/process.c +++ b/arch/parisc/kernel/process.c @@ -224,7 +224,7 @@ copy_thread(struct task_struct *p, const struct kernel_clone_args *args) if (unlikely(p->flags & (PF_KTHREAD | PF_IO_WORKER))) { /* kernel thread */ memset(cregs, 0, sizeof(struct pt_regs)); - if (!usp) /* idle thread */ + if (args->idle) /* idle thread */ return 0; /* Must exit via ret_from_kernel_thread in order * to call schedule_tail() diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index fcdcba231aac..3d6b99ce5408 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -33,6 +33,7 @@ struct kernel_clone_args { int cgroup; int io_thread; int kthread; + int idle; struct cgroup *cgrp; struct css_set *cset; }; diff --git a/kernel/fork.c b/kernel/fork.c index d39a248a8d8d..93d77ee921ff 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -2544,12 +2544,21 @@ static inline void init_idle_pids(struct task_struct *idle) } } +static int idle_dummy(void *dummy) +{ + /* This function is never called */ + return 0; +} + struct task_struct * __init fork_idle(int cpu) { struct task_struct *task; struct kernel_clone_args args = { .flags = CLONE_VM, + .stack = (unsigned long)&idle_dummy, + .stack_size = (unsigned long)NULL, .kthread = 1, + .idle = 1, }; task = copy_process(&init_struct_pid, 0, cpu_to_node(cpu), &args); -- 2.35.3