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 3A45EC433EF for ; Wed, 20 Apr 2022 11:36:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356819AbiDTLiz (ORCPT ); Wed, 20 Apr 2022 07:38:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45818 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1357055AbiDTLit (ORCPT ); Wed, 20 Apr 2022 07:38:49 -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 15C0D4160D for ; Wed, 20 Apr 2022 04:36:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1650454561; 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=d4N4aySfLdtOlqYeiwulC0vSXKCn/tdHTX38ZaFwcP8=; b=RYytNF6ym+Mu9tpYHnT+7Sl3aTydfzAZ/mTJvTScsGRYjbLR8BtsZXRTuq0nWfEHe1DOBC +9+1+ij6U+HX2bht8cfLHm9GXNHkKC8xnd88vEEce/EoEbCdZyLn6b7HLKb5Vv/NwHM5f8 RdZo4+FqiqlGamavCI1A4DBVnuavw7k= 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-21-ohOHLoVhNe-LFcUl1gEhqw-1; Wed, 20 Apr 2022 07:35:53 -0400 X-MC-Unique: ohOHLoVhNe-LFcUl1gEhqw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 245711C0512A; Wed, 20 Apr 2022 11:35:53 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.193.5]) by smtp.corp.redhat.com (Postfix) with SMTP id 282534639F6; Wed, 20 Apr 2022 11:35:49 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Wed, 20 Apr 2022 13:35:52 +0200 (CEST) Date: Wed, 20 Apr 2022 13:35:48 +0200 From: Oleg Nesterov To: Peter Zijlstra Cc: rjw@rjwysocki.net, mingo@kernel.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, mgorman@suse.de, ebiederm@xmission.com, bigeasy@linutronix.de, Will Deacon , linux-kernel@vger.kernel.org, tj@kernel.org, linux-pm@vger.kernel.org Subject: Re: [PATCH 2/5] sched,ptrace: Fix ptrace_check_attach() vs PREEMPT_RT Message-ID: <20220420113547.GA16575@redhat.com> References: <20220413185704.GA30360@redhat.com> <20220413185909.GB30360@redhat.com> <20220413192053.GY2731@worktop.programming.kicks-ass.net> <20220413195612.GC2762@worktop.programming.kicks-ass.net> <20220414115410.GA32752@redhat.com> <20220414183433.GC32752@redhat.com> <20220415101644.GA10421@redhat.com> <20220415105755.GA15217@redhat.com> <20220420102006.GD2731@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220420102006.GD2731@worktop.programming.kicks-ass.net> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.85 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/20, Peter Zijlstra wrote: > > On Fri, Apr 15, 2022 at 12:57:56PM +0200, Oleg Nesterov wrote: > > > > ptrace_resume() does wake_up_state(child, __TASK_TRACED) but doesn't > > clear JOBCTL_TRACED. The "else" branch in ptrace_stop() leaks this flag > > too. Perhaps I missed something, I'll reread 1/5 again, but the main > > question to me is whether 1-2 actually need the JOBCTL_TRACED_FROZEN flag. > > Ok, getting back to this. So I did the change to ptrace_resume(), but > I'm not entirely sure I understand the issue with the else branch of > ptrace_stop(). > > My understanding is that if we hit that else branch, we've raced wth > __ptrace_unlink(), and that will have done: Yes, thanks for correcting me, I forgot that may_ptrace_stop() has gone. Oleg.