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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,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 F0963C433FF for ; Wed, 31 Jul 2019 06:26:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CE05C206A3 for ; Wed, 31 Jul 2019 06:26:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727478AbfGaG0h (ORCPT ); Wed, 31 Jul 2019 02:26:37 -0400 Received: from smtprelay0019.hostedemail.com ([216.40.44.19]:48876 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726652AbfGaG0h (ORCPT ); Wed, 31 Jul 2019 02:26:37 -0400 Received: from filter.hostedemail.com (clb03-v110.bra.tucows.net [216.40.38.60]) by smtprelay02.hostedemail.com (Postfix) with ESMTP id D38943811; Wed, 31 Jul 2019 06:26:35 +0000 (UTC) X-Session-Marker: 6A6F6540706572636865732E636F6D X-HE-Tag: error57_395f5308c0426 X-Filterd-Recvd-Size: 2802 Received: from XPS-9350.home (cpe-23-242-196-136.socal.res.rr.com [23.242.196.136]) (Authenticated sender: joe@perches.com) by omf07.hostedemail.com (Postfix) with ESMTPA; Wed, 31 Jul 2019 06:26:34 +0000 (UTC) Message-ID: <29b3741ca8a9e94d64dba213059abb2296c30936.camel@perches.com> Subject: Re: [PATCH v2] 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 23:26:32 -0700 In-Reply-To: <20190731062416.26238-1-huangfq.daxian@gmail.com> References: <20190731062416.26238-1-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 14:24 +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 in IRQ context. > Link: https://lwn.net/Articles/365835 > > Reviewed-by: Joe Perches I made a suggestion. I did not review this. Please do not add signatures like this if not specifically given by someone. > Signed-off-by: Fuqian Huang > --- > Changes in v2: > - Only make the interrupt uses the trace_printk to avoid > all 4000+ drm_dbg/DRM_DEBUG uses emitting a trace_printk. > > drivers/gpu/drm/drm_print.c | 10 +++++++--- > 1 file changed, 7 insertions(+), 3 deletions(-) > > diff --git a/drivers/gpu/drm/drm_print.c b/drivers/gpu/drm/drm_print.c > index a17c8a14dba4..747835d16fa6 100644 > --- a/drivers/gpu/drm/drm_print.c > +++ b/drivers/gpu/drm/drm_print.c > @@ -236,9 +236,13 @@ void drm_dbg(unsigned int category, const char *format, ...) > vaf.fmt = format; > vaf.va = &args; > > - printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", > - __builtin_return_address(0), &vaf); > - > + if (in_interrupt()) { > + trace_printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", > + __builtin_return_address(0), &vaf); > + } else { > + printk(KERN_DEBUG "[" DRM_NAME ":%ps] %pV", > + __builtin_return_address(0), &vaf); > + } > va_end(args); > } > EXPORT_SYMBOL(drm_dbg);