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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE 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 33213C433B4 for ; Mon, 19 Apr 2021 18:47:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F0A6C61285 for ; Mon, 19 Apr 2021 18:47:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241096AbhDSSrh (ORCPT ); Mon, 19 Apr 2021 14:47:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47078 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233736AbhDSSrf (ORCPT ); Mon, 19 Apr 2021 14:47:35 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1E865C06174A for ; Mon, 19 Apr 2021 11:47:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=fibG0vpbii9Ivs6Gs0ea/QNMyUGprQ7QSnQOApj2WM4=; b=B/Uw02MbJTvidnKFUVyQWsfnKf aE8oG91QWy1H33PISIlh505qdyIO66rXCGTJmpHBOEOjX5dz5tpwttokIWVTGTOCOddEjA4a77Dkx rIxvduTZZjz059dWOGdpH7SIC1uEJileuizQ4jvX0wzrjPK5tDU4eYBROyHm7N9w9jw//GOvTskRD qC46r/Rr4ksUWfwZrBMZ9ruyfZzPtYnrCpIsWlmqILanu67kfG743irro840jsNkDO6e2jw0Bze3M 6MfvWDTxT/He6nwGIIn1+vcZfJmau3fVZXdWovvgQ/8nbeQqmyqVxPEIbzMG9yqQa+4lY/tZg8s89 QcBsGhFg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=worktop.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.94 #2 (Red Hat Linux)) id 1lYYuA-00E9Uz-Kk; Mon, 19 Apr 2021 18:46:06 +0000 Received: by worktop.programming.kicks-ass.net (Postfix, from userid 1000) id 5EE9B980D8D; Mon, 19 Apr 2021 20:45:53 +0200 (CEST) Date: Mon, 19 Apr 2021 20:45:53 +0200 From: Peter Zijlstra To: Valentin Schneider Cc: syzbot , bp@alien8.de, dwmw@amazon.co.uk, hpa@zytor.com, linux-kernel@vger.kernel.org, luto@kernel.org, mingo@redhat.com, syzkaller-bugs@googlegroups.com, tglx@linutronix.de, x86@kernel.org Subject: Re: [syzbot] WARNING in kthread_is_per_cpu Message-ID: <20210419184553.GA26214@worktop.programming.kicks-ass.net> References: <000000000000a61f7705c050e601@google.com> <87im4ilddh.mognet@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87im4ilddh.mognet@arm.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 19, 2021 at 12:31:22PM +0100, Valentin Schneider wrote: > if ((p->flags & PF_KTHREAD) && kthread_is_per_cpu(p)) > `\ > to_kthread(p); > `\ > WARN_ON(!(p->flags & PF_KTHREAD)); > > ... Huh? Something like so perhaps? diff --git a/kernel/kthread.c b/kernel/kthread.c index 1578973c5740..eeba40df61ac 100644 --- a/kernel/kthread.c +++ b/kernel/kthread.c @@ -78,6 +78,14 @@ static inline void set_kthread_struct(void *kthread) current->set_child_tid = (__force void __user *)kthread; } +static inline struct kthread *__to_kthread(struct task_struct *k) +{ + void *kthread = (__force void *)k->set_child_tid; + if (kthread && !(k->flags & PF_KTHREAD)) + kthread = NULL; + return kthread; +} + static inline struct kthread *to_kthread(struct task_struct *k) { WARN_ON(!(k->flags & PF_KTHREAD)); @@ -516,7 +524,7 @@ void kthread_set_per_cpu(struct task_struct *k, int cpu) bool kthread_is_per_cpu(struct task_struct *k) { - struct kthread *kthread = to_kthread(k); + struct kthread *kthread = __to_kthread(k); if (!kthread) return false; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3384ea74cad4..dc6311bd6986 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7658,7 +7658,7 @@ static void balance_push(struct rq *rq) * histerical raisins. */ if (rq->idle == push_task || - ((push_task->flags & PF_KTHREAD) && kthread_is_per_cpu(push_task)) || + kthread_is_per_cpu(push_task) || is_migration_disabled(push_task)) { /*