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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no 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 9F1C2C433FF for ; Wed, 31 Jul 2019 06:06:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7CEFD206A3 for ; Wed, 31 Jul 2019 06:06:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726927AbfGaGG1 (ORCPT ); Wed, 31 Jul 2019 02:06:27 -0400 Received: from smtprelay0045.hostedemail.com ([216.40.44.45]:56288 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725209AbfGaGG0 (ORCPT ); Wed, 31 Jul 2019 02:06:26 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay05.hostedemail.com (Postfix) with ESMTP id 692871802E6E7; Wed, 31 Jul 2019 06:06:25 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: door01_1ac50e83e2663 X-Filterd-Recvd-Size: 2235 Received: from XPS-9350 (cpe-23-242-196-136.socal.res.rr.com [23.242.196.136]) (Authenticated sender: joe@perches.com) by omf06.hostedemail.com (Postfix) with ESMTPA; Wed, 31 Jul 2019 06:06:23 +0000 (UTC) Message-ID: <520bd0f7367e77ffd2e0150187f6ffb64b0e8b71.camel@perches.com> Subject: Re: [PATCH] drm: use trace_printk rather than printk in drm_dbg. From: Joe Perches To: Fuqian Huang Cc: Maarten Lankhorst , Maxime Ripard , Sean Paul , David Airlie , Daniel Vetter , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Date: Tue, 30 Jul 2019 23:06:22 -0700 In-Reply-To: <20190731024533.22264-1-huangfq.daxian@gmail.com> References: <20190731024533.22264-1-huangfq.daxian@gmail.com> Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.30.5-0ubuntu0.18.10.1 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2019-07-31 at 10:45 +0800, Fuqian Huang wrote: > In drivers/gpu/drm/amd/amdgpu/amdgpu_ih.c, > amdgpu_ih_process calls DRM_DEBUG which calls drm_dbg and > finally calls printk. > As amdgpu_ih_process is called from an interrupt handler, > and interrupt handler should be short as possible. > > As printk may lead to bogging down the system or can even > create a live lock. printk should not be used in IRQ context. > Instead, trace_printk is recommended. > Link: https://lwn.net/Articles/365835 [] > diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c [] > @@ -236,7 +236,7 @@ void drm_dbg(unsigned int category, const char *format, ...) > vaf.fmt = format; > vaf.va = &args; > > - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", > + trace_printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", > __builtin_return_address(0), &vaf); > > va_end(args); This makes all 4000+ drm_dbg/DRM_DEBUG uses emit a trace_printk. I suggest instead you make only the interrupt uses use a different function and not drm_dbg. Or maybe add an in_interrupt() check like if (in_interrupt()) printk(KERN_DEBUG etc...) else trace_printk(etc...)