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 0A1D1C433F5 for ; Thu, 28 Apr 2022 16:10:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1349516AbiD1QNo (ORCPT ); Thu, 28 Apr 2022 12:13:44 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54676 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230216AbiD1QNn (ORCPT ); Thu, 28 Apr 2022 12:13:43 -0400 Received: from desiato.infradead.org (desiato.infradead.org [IPv6:2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0317B11C03; Thu, 28 Apr 2022 09:10:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; 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=Lg8SqQYCcNFGIKioQXjUK2uICLPTc1JMobWkPo+n0W8=; b=QQjuN2cWLD2QjLNCxlFpCNSYOl YgRRXme+rrRbihUv5AuBfn2TfzHJpmudJquvxC9wp5DQY5QDZQHKbkPIfonWw0z87lTFSmXRdWC8G bkZT9F5/eR7ZPuf1TEFCOkDAXUIItjikmTOyUkrUPPMzP9A5Lf7e2jR6pMb4G6LoIGv1+cSvGBQRJ dzsIyjuSiQH6/mwgYkbuuNHfDTTbkiPgHkXbMZ/HoHrPHumFj7hx1S9jlN/Cybv9c5cguOGbxGzWs 8Ewx4M5gL3u7LRkeMltPCf2/4nLnDNUrqA7h18kF/NAW/6AWB9h5pPsT3wRbV2+Na0gfBJ2XRxDjc C+RNX82Q==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by desiato.infradead.org with esmtpsa (Exim 4.94.2 #2 (Red Hat Linux)) id 1nk6iK-009Muv-UM; Thu, 28 Apr 2022 16:09:57 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 0AB7D30031D; Thu, 28 Apr 2022 18:09:53 +0200 (CEST) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id DF3592029F886; Thu, 28 Apr 2022 18:09:53 +0200 (CEST) Date: Thu, 28 Apr 2022 18:09:53 +0200 From: Peter Zijlstra To: Oleg Nesterov 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: 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: <20220428145750.GA15485@redhat.com> Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org 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. 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);