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=-12.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 A12DEC433C1 for ; Thu, 25 Mar 2021 18:28:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 51B9361A33 for ; Thu, 25 Mar 2021 18:28:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229833AbhCYS2M (ORCPT ); Thu, 25 Mar 2021 14:28:12 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:27887 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229533AbhCYS1q (ORCPT ); Thu, 25 Mar 2021 14:27:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1616696866; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2VMhsAZwrflDKUGyUEkwUGTMaYhk4RiBpO9SY7d/GvA=; b=CJqOGt2OLW24Dcr4fIdYSQiVxUH7WaqilE2ba95Jtzy/5s3HI0cs2kuaHdWAhSMCr90YiE +prRRoPfXw/XDKO72GEFtRxOIKkHVRmZO4IDnW2S5K98ntMKeji/Cjvi+2hlXaYQCKSOpy PSlTnL31+clXvE85jTSla68xnCH+OGM= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-161-hZL5rhMhOXOZJtL5r9omZQ-1; Thu, 25 Mar 2021 14:27:42 -0400 X-MC-Unique: hZL5rhMhOXOZJtL5r9omZQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 73AAA87A82A; Thu, 25 Mar 2021 18:27:39 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.41]) by smtp.corp.redhat.com (Postfix) with SMTP id 18E4260CCF; Thu, 25 Mar 2021 18:27:36 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 25 Mar 2021 19:27:39 +0100 (CET) Date: Thu, 25 Mar 2021 19:27:35 +0100 From: Oleg Nesterov To: Peter Zijlstra Cc: Thomas Gleixner , Sebastian Andrzej Siewior , linux-kernel@vger.kernel.org, adobriyan@gmail.com, Linus Torvalds , Ingo Molnar , Steven Rostedt Subject: Re: [RFC][PATCH] task_struct::state frobbing Message-ID: <20210325182735.GA28349@redhat.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/25, Peter Zijlstra wrote: > > static void ptrace_unfreeze_traced(struct task_struct *task) > { > - if (task->state != __TASK_TRACED) > + if (READ_ONCE(task->__state) != __TASK_TRACED) > return; this change is correct, > @@ -201,11 +201,11 @@ static void ptrace_unfreeze_traced(struct task_struct *task) > * Recheck state under the lock to close this race. > */ > spin_lock_irq(&task->sighand->siglock); > - if (task->state == __TASK_TRACED) { > + if (READ_ONCE(task->__state) == __TASK_TRACED) { this too, > @@ -240,7 +240,7 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) > */ > read_lock(&tasklist_lock); > if (child->ptrace && child->parent == current) { > - WARN_ON(child->state == __TASK_TRACED); > + WARN_ON(task_is_traced(child)); > /* > * child->sighand can't be NULL, release_task() > * does ptrace_unlink() before __exit_signal(). > @@ -257,7 +257,7 @@ static int ptrace_check_attach(struct task_struct *child, bool ignore_state) > * ptrace_stop() changes ->state back to TASK_RUNNING, > * so we should not worry about leaking __TASK_TRACED. > */ > - WARN_ON(child->state == __TASK_TRACED); > + WARN_ON(task_is_traced(child)); the two above are not. "state == __TASK_TRACED" and task_is_traced() is not the same thing. "state == __TASK_TRACED" means that debugger changed the state from TASK_TRACED to __TASK_TRACED (iow, removed TASK_WAKEKILL) to ensure the tracee can not run, this doesn't affect task_is_traced(). Oleg.