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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B7C3DC10F11 for ; Wed, 24 Apr 2019 18:49:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8B508208E4 for ; Wed, 24 Apr 2019 18:49:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728100AbfDXStA (ORCPT ); Wed, 24 Apr 2019 14:49:00 -0400 Received: from mx2.suse.de ([195.135.220.15]:56218 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726176AbfDXSs7 (ORCPT ); Wed, 24 Apr 2019 14:48:59 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 980EAACD8; Wed, 24 Apr 2019 18:48:58 +0000 (UTC) Date: Wed, 24 Apr 2019 20:48:58 +0200 (CEST) From: Miroslav Benes To: Josh Poimboeuf cc: Petr Mladek , Jiri Kosina , Joe Lawrence , Kamalesh Babulal , live-patching@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/3] livepatch: Cleanup message handling in klp_try_switch_task() In-Reply-To: <20190424155532.3uyxyxwm4c5dqsf5@treble> Message-ID: References: <20190424085550.29612-1-pmladek@suse.com> <20190424085550.29612-4-pmladek@suse.com> <20190424155532.3uyxyxwm4c5dqsf5@treble> User-Agent: Alpine 2.21 (LSU 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 24 Apr 2019, Josh Poimboeuf wrote: > On Wed, Apr 24, 2019 at 10:55:50AM +0200, Petr Mladek wrote: > > WARN_ON_ONCE() could not be called safely under rq lock because > > of console deadlock issues. Fortunately, simple printk_deferred() > > is enough because the warning is printed from a well defined > > location and context. > > > > Also klp_try_switch_task() is called under klp_mutex. > > Therefore, the buffer for debug messages could be static. > > > > Signed-off-by: Petr Mladek > > --- > > kernel/livepatch/transition.c | 19 ++++++++++++++----- > > 1 file changed, 14 insertions(+), 5 deletions(-) > > > > diff --git a/kernel/livepatch/transition.c b/kernel/livepatch/transition.c > > index 9c89ae8b337a..e8183d18227f 100644 > > --- a/kernel/livepatch/transition.c > > +++ b/kernel/livepatch/transition.c > > @@ -254,6 +254,7 @@ static int klp_check_stack_func(struct klp_func *func, > > static int klp_check_stack(struct task_struct *task, char *err_buf) > > { > > static unsigned long entries[MAX_STACK_ENTRIES]; > > + static int enosys_warned; > > struct stack_trace trace; > > struct klp_object *obj; > > struct klp_func *func; > > @@ -263,8 +264,16 @@ static int klp_check_stack(struct task_struct *task, char *err_buf) > > trace.nr_entries = 0; > > trace.max_entries = MAX_STACK_ENTRIES; > > trace.entries = entries; > > + > > ret = save_stack_trace_tsk_reliable(task, &trace); > > - WARN_ON_ONCE(ret == -ENOSYS); > > + if (ret == -ENOSYS) { > > + if (!enosys_warned) { > > + printk_deferred(KERN_WARNING "%s: save_stack_trace_tsk_reliable() not supported on this architecture.\n", > > + __func__); > > + enosys_warned = 1; > > + } > > + return ret; > > + } > > We already have a similar printk in patch 1, so is this warning really > needed? I don't think so. pr_warn() in klp_enable_patch() should be enough in my opinion. However, if (ret == -ENOSYS) return ret; would be justified, wouldn't it? Miroslav