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 20BC5C433F5 for ; Tue, 24 May 2022 13:26:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237778AbiEXN03 (ORCPT ); Tue, 24 May 2022 09:26:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58922 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237853AbiEXN0U (ORCPT ); Tue, 24 May 2022 09:26:20 -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 B98FF50E0B for ; Tue, 24 May 2022 06:26:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1653398777; 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=acmhyrCTF0XS2BK7y8uo6vpek2Tjc12pUbIZAJf3+G4=; b=A11QgoEV5TVCopQJaaR4wiynfBt2qGkcqDES3ko6plRADd6xfZhJ7H4l/SjGxZT6EAC+fI A2YzyyG6h1dv9rSQVWzxri4qSB8Bp9wHWXatGb55vfiNPd5611HMJLm6avRgBd+nnBUFoB NPlCe5S6nDRjjMiyzhm/Z79BN+1xPU4= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-235-k95FiaAWOuuZHyhIgKfnnw-1; Tue, 24 May 2022 09:26:16 -0400 X-MC-Unique: k95FiaAWOuuZHyhIgKfnnw-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 C2D89803D5B; Tue, 24 May 2022 13:26:14 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.40.195.109]) by smtp.corp.redhat.com (Postfix) with SMTP id B31637AD8; Tue, 24 May 2022 13:25:55 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 24 May 2022 15:26:14 +0200 (CEST) Date: Tue, 24 May 2022 15:25:54 +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, Robert OCallahan , Kyle Huey , Richard Henderson , Ivan Kokshaysky , Matt Turner , Jason Wessel , Daniel Thompson , Douglas Anderson , Douglas Miller , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras Subject: Re: [PATCH 07/16] signal: Wake up the designated parent Message-ID: <20220524132553.GD14347@redhat.com> References: <871qwq5ucx.fsf_-_@email.froward.int.ebiederm.org> <20220518225355.784371-7-ebiederm@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220518225355.784371-7-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-kernel@vger.kernel.org I fail to understand this patch... On 05/18, Eric W. Biederman wrote: > > Today if a process is ptraced only the ptracer will ever be woken up in > wait and why is this wrong? > Fixes: 75b95953a569 ("job control: Add @for_ptrace to do_notify_parent_cldstop()") how does this change fix 75b95953a569? > static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode, > int sync, void *key) > { > struct wait_opts *wo = container_of(wait, struct wait_opts, > child_wait); > - struct task_struct *p = key; > + struct child_wait_info *info = key; > > - if (!eligible_pid(wo, p)) > + if (!eligible_pid(wo, info->p)) > return 0; > > - if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent) > - return 0; > + if ((wo->wo_flags & __WNOTHREAD) && (wait->private != info->parent)) > + return 0; So. wait->private is the task T which sleeping on wait_chldexit. Before the patch the logic is clear. T called do_wait(__WNOTHREAD) and we do not need to wake it up if it is not the "actual" parent of p. After the patch we check it T is actual to the "parent" arg passed to __wake_up_parent(). Why??? This arg is only used to find the ->signal->wait_chldexit wait_queue_head, and this is fine. As I said, I don't understand this patch. But at least this change is wrong in case when __wake_up_parent() is calles by __ptrace_detach(). (you removed it in 5/16 but this looks wrong too). Sure, we can change ptrace_detach() to use __wake_up_parent(p, p->parent), but for what? I must have missed something. Oleg. From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1ntUYL-0086Xr-4e for linux-um@lists.infradead.org; Tue, 24 May 2022 13:26:26 +0000 Date: Tue, 24 May 2022 15:25:54 +0200 From: Oleg Nesterov Subject: Re: [PATCH 07/16] signal: Wake up the designated parent Message-ID: <20220524132553.GD14347@redhat.com> References: <871qwq5ucx.fsf_-_@email.froward.int.ebiederm.org> <20220518225355.784371-7-ebiederm@xmission.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20220518225355.784371-7-ebiederm@xmission.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-um" Errors-To: linux-um-bounces+geert=linux-m68k.org@lists.infradead.org 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, Robert OCallahan , Kyle Huey , Richard Henderson , Ivan Kokshaysky , Matt Turner , Jason Wessel , Daniel Thompson , Douglas Anderson , Douglas Miller , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras I fail to understand this patch... On 05/18, Eric W. Biederman wrote: > > Today if a process is ptraced only the ptracer will ever be woken up in > wait and why is this wrong? > Fixes: 75b95953a569 ("job control: Add @for_ptrace to do_notify_parent_cldstop()") how does this change fix 75b95953a569? > static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode, > int sync, void *key) > { > struct wait_opts *wo = container_of(wait, struct wait_opts, > child_wait); > - struct task_struct *p = key; > + struct child_wait_info *info = key; > > - if (!eligible_pid(wo, p)) > + if (!eligible_pid(wo, info->p)) > return 0; > > - if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent) > - return 0; > + if ((wo->wo_flags & __WNOTHREAD) && (wait->private != info->parent)) > + return 0; So. wait->private is the task T which sleeping on wait_chldexit. Before the patch the logic is clear. T called do_wait(__WNOTHREAD) and we do not need to wake it up if it is not the "actual" parent of p. After the patch we check it T is actual to the "parent" arg passed to __wake_up_parent(). Why??? This arg is only used to find the ->signal->wait_chldexit wait_queue_head, and this is fine. As I said, I don't understand this patch. But at least this change is wrong in case when __wake_up_parent() is calles by __ptrace_detach(). (you removed it in 5/16 but this looks wrong too). Sure, we can change ptrace_detach() to use __wake_up_parent(p, p->parent), but for what? I must have missed something. Oleg. _______________________________________________ linux-um mailing list linux-um@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-um From mboxrd@z Thu Jan 1 00:00:00 1970 From: Oleg Nesterov Date: Tue, 24 May 2022 13:25:54 +0000 Subject: Re: [PATCH 07/16] signal: Wake up the designated parent Message-Id: <20220524132553.GD14347@redhat.com> List-Id: References: <871qwq5ucx.fsf_-_@email.froward.int.ebiederm.org> <20220518225355.784371-7-ebiederm@xmission.com> In-Reply-To: <20220518225355.784371-7-ebiederm@xmission.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit 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, Robert OCallahan , Kyle Huey , Richard Henderson , Ivan Kokshaysky , Matt Turner , Jason Wessel , Daniel Thompson , Douglas Anderson , Douglas Miller , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras I fail to understand this patch... On 05/18, Eric W. Biederman wrote: > > Today if a process is ptraced only the ptracer will ever be woken up in > wait and why is this wrong? > Fixes: 75b95953a569 ("job control: Add @for_ptrace to do_notify_parent_cldstop()") how does this change fix 75b95953a569? > static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode, > int sync, void *key) > { > struct wait_opts *wo = container_of(wait, struct wait_opts, > child_wait); > - struct task_struct *p = key; > + struct child_wait_info *info = key; > > - if (!eligible_pid(wo, p)) > + if (!eligible_pid(wo, info->p)) > return 0; > > - if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent) > - return 0; > + if ((wo->wo_flags & __WNOTHREAD) && (wait->private != info->parent)) > + return 0; So. wait->private is the task T which sleeping on wait_chldexit. Before the patch the logic is clear. T called do_wait(__WNOTHREAD) and we do not need to wake it up if it is not the "actual" parent of p. After the patch we check it T is actual to the "parent" arg passed to __wake_up_parent(). Why??? This arg is only used to find the ->signal->wait_chldexit wait_queue_head, and this is fine. As I said, I don't understand this patch. But at least this change is wrong in case when __wake_up_parent() is calles by __ptrace_detach(). (you removed it in 5/16 but this looks wrong too). Sure, we can change ptrace_detach() to use __wake_up_parent(p, p->parent), but for what? I must have missed something. Oleg.