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 2E071C433F5 for ; Mon, 2 May 2022 15:47:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1385978AbiEBPuw (ORCPT ); Mon, 2 May 2022 11:50:52 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58472 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348614AbiEBPuv (ORCPT ); Mon, 2 May 2022 11:50:51 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B9AA111C06 for ; Mon, 2 May 2022 08:47:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1651506441; 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=/b/wf3TlWHf9Zjpyk+RTfXxkRyQ7N7k9txwQlidxwcU=; b=ZPwS0IJviKIkdHXenGG3MDkBPAIu+j/HZTtVTzphaQ1YsQXgcuJkmcox/S6bQJo7Iqp/lO GppjC9s+sI9rLGmkW6yVpHLeej67nQmhaMxunbau0HI/EdPtXgipt/TLNGq9fuxfWIckAw YulFXkoV3DEFRpxjEp4gHdGcU6ZOsvk= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-45-odXXuIkvOQOAXangaYPWDQ-1; Mon, 02 May 2022 11:47:15 -0400 X-MC-Unique: odXXuIkvOQOAXangaYPWDQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 460001E10B42; Mon, 2 May 2022 15:47:14 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.34]) by smtp.corp.redhat.com (Postfix) with SMTP id 8BEDD9E60; Mon, 2 May 2022 15:47:09 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Mon, 2 May 2022 17:47:13 +0200 (CEST) Date: Mon, 2 May 2022 17:47:08 +0200 From: Oleg Nesterov To: "Eric W. Biederman" Cc: linux-kernel@vger.kernel.org, rjw@rjwysocki.net, mingo@kernel.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, mgorman@suse.de, bigeasy@linutronix.de, Will Deacon , tj@kernel.org, linux-pm@vger.kernel.org, Peter Zijlstra , Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org, Chris Zankel , Max Filippov , linux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn , linux-ia64@vger.kernel.org Subject: Re: [PATCH v2 07/12] ptrace: Don't change __state Message-ID: <20220502154708.GE17276@redhat.com> References: <87k0b7v9yk.fsf_-_@email.froward.int.ebiederm.org> <20220429214837.386518-7-ebiederm@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220429214837.386518-7-ebiederm@xmission.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 04/29, Eric W. Biederman wrote: > > static void ptrace_unfreeze_traced(struct task_struct *task) > { > - if (READ_ONCE(task->__state) != __TASK_TRACED) > - return; > - > - WARN_ON(!task->ptrace || task->parent != current); > + unsigned long flags; > > /* > - * PTRACE_LISTEN can allow ptrace_trap_notify to wake us up remotely. > - * Recheck state under the lock to close this race. > + * The child may be awake and may have cleared > + * JOBCTL_PTRACE_FROZEN (see ptrace_resume). The child will > + * not set JOBCTL_PTRACE_FROZEN or enter __TASK_TRACED anew. > */ > - spin_lock_irq(&task->sighand->siglock); > - if (READ_ONCE(task->__state) == __TASK_TRACED) { > + if (lock_task_sighand(task, &flags)) { > + task->jobctl &= ~JOBCTL_PTRACE_FROZEN; Well, I think that the fast-path if (!(task->jobctl & JOBCTL_PTRACE_FROZEN)) return; at the start makes sense, we can avoid lock_task_sighand() if the tracee was resumed. Oleg.