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=-7.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED 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 A7F85C10F11 for ; Wed, 24 Apr 2019 10:41:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 764092084F for ; Wed, 24 Apr 2019 10:41:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556102466; bh=F3A71PrMdLdNdQbOEHMWMx2WAB5ZlMboAMxAGcWPPms=; h=Date:From:To:cc:Subject:In-Reply-To:References:List-ID:From; b=FmBshi82PanOqd93VDzWIR4ICFGwcddy9q0UlER5djliS3mbug5atuJv89L7WBmd0 2VbD/Rj8h/UWQxfx+csw8MwHyhTH/Eodmz628pyvOimkfEhwVEZe5z17/1yla4Ewwp RBK/Fqq5h/C7mWL6vbMdTBPrnAzppFM7fug46cx4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728448AbfDXKlF (ORCPT ); Wed, 24 Apr 2019 06:41:05 -0400 Received: from mail.kernel.org ([198.145.29.99]:40086 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726550AbfDXKlF (ORCPT ); Wed, 24 Apr 2019 06:41:05 -0400 Received: from pobox.suse.cz (prg-ext-pat.suse.com [213.151.95.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B3CD62084F; Wed, 24 Apr 2019 10:41:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1556102464; bh=F3A71PrMdLdNdQbOEHMWMx2WAB5ZlMboAMxAGcWPPms=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=m/dNok4jUlWbd9Iq9jF0Vs+HcWQNHf7eUYWPd3IhDapP923nE/2AbVeMKMVmhjD7T IZboCOgXkCyFMfYXL68Ve7U6MrYO7Hm0lAt9KcajgAbbo/h5DpS++buY2XQYVqgn/A gim06cvPhpQhr8AHPXhd2agwt0cy6+iz23eOzRqM= Date: Wed, 24 Apr 2019 12:41:00 +0200 (CEST) From: Jiri Kosina To: Petr Mladek cc: Josh Poimboeuf , Miroslav Benes , 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: <20190424085550.29612-4-pmladek@suse.com> Message-ID: References: <20190424085550.29612-1-pmladek@suse.com> <20190424085550.29612-4-pmladek@suse.com> 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, 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; ... abusing the fact that you are also printk maintainer :) ... looking at the above, wouldn't it make sense to introduce generic printk_deferred_once() instead? -- Jiri Kosina SUSE Labs