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 06B19C433F5 for ; Thu, 28 Apr 2022 16:19:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349881AbiD1QWl (ORCPT ); Thu, 28 Apr 2022 12:22:41 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48598 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1349882AbiD1QWj (ORCPT ); Thu, 28 Apr 2022 12:22:39 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 14E845D18B for ; Thu, 28 Apr 2022 09:19:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1651162762; 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=TK2deUlPmpF496ha3AlCXcsfEwKXNp+OVKjxx1+ZfjM=; b=Gv1bfTsI+TrgNDhD8WD/tCPXb02WDIilygyU8piHSDtGu44SNmaaJYUnUgnMJNnId5GGVT F2luKTAY2xlJKw3xzvs10n+NmHD3f5QBZPNq+97AF7QMCN5EkmV2utHd/rr9P3oZluAt8W S2doTYlhMbBjsy6mA4c0zDQVr/HJ59s= 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-466-AYxnPGG8MouLzDRXcZQYXQ-1; Thu, 28 Apr 2022 12:19:20 -0400 X-MC-Unique: AYxnPGG8MouLzDRXcZQYXQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id A068929ABA25; Thu, 28 Apr 2022 16:19:19 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.192.151]) by smtp.corp.redhat.com (Postfix) with SMTP id B184615230A0; Thu, 28 Apr 2022 16:19:14 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Thu, 28 Apr 2022 18:19:19 +0200 (CEST) Date: Thu, 28 Apr 2022 18:19:13 +0200 From: Oleg Nesterov To: Peter Zijlstra Cc: "Eric W. Biederman" , 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, Richard Weinberger , Anton Ivanov , Johannes Berg , linux-um@lists.infradead.org, Chris Zankel , Max Filippov , inux-xtensa@linux-xtensa.org, Kees Cook , Jann Horn Subject: Re: [PATCH 7/9] ptrace: Simplify the wait_task_inactive call in ptrace_check_attach Message-ID: <20220428161912.GD15485@redhat.com> References: <878rrrh32q.fsf_-_@email.froward.int.ebiederm.org> <20220426225211.308418-7-ebiederm@xmission.com> <20220427151455.GE17421@redhat.com> <20220428111911.GA3804@redhat.com> <20220428145750.GA15485@redhat.com> 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 2.85 on 10.11.54.7 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org On 04/28, Peter Zijlstra wrote: > > On Thu, Apr 28, 2022 at 04:57:50PM +0200, Oleg Nesterov wrote: > > > > Shouldn't we then switch wait_task_inactive() so have & matching instead > > > of the current ==. > > > > Sorry, I don't understand the context... > > This.. I've always found it strange to have wti use a different matching > scheme from ttwu. Ah. This is what I understood (and I too thought about this), just I meant that this patch from Eric (assuming wait_task_inactive() still uses __TASK_TRACED) is fine without your change below. Oleg. > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index f259621f4c93..c039aef4c8fe 100644 > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -3304,7 +3304,7 @@ unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state > * is actually now running somewhere else! > */ > while (task_running(rq, p)) { > - if (match_state && unlikely(READ_ONCE(p->__state) != match_state)) > + if (match_state && unlikely(!(READ_ONCE(p->__state) & match_state))) > return 0; > cpu_relax(); > } > @@ -3319,7 +3319,7 @@ unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state > running = task_running(rq, p); > queued = task_on_rq_queued(p); > ncsw = 0; > - if (!match_state || READ_ONCE(p->__state) == match_state) > + if (!match_state || (READ_ONCE(p->__state) & match_state)) > ncsw = p->nvcsw | LONG_MIN; /* sets MSB */ > task_rq_unlock(rq, p, &rf);