From patchwork Fri Dec 18 16:18:36 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Petr Mladek X-Patchwork-Id: 7886951 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id F030D9F1AF for ; Fri, 18 Dec 2015 16:20:41 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 09D46204B0 for ; Fri, 18 Dec 2015 16:20:41 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 1D5AB204AF for ; Fri, 18 Dec 2015 16:20:40 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1a9xkF-0005Ej-UM; Fri, 18 Dec 2015 16:19:03 +0000 Received: from mx2.suse.de ([195.135.220.15]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1a9xkC-00059H-K4 for linux-arm-kernel@lists.infradead.org; Fri, 18 Dec 2015 16:19:01 +0000 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (charybdis-ext.suse.de [195.135.220.254]) by mx2.suse.de (Postfix) with ESMTP id 11D68AAB2; Fri, 18 Dec 2015 16:18:37 +0000 (UTC) Date: Fri, 18 Dec 2015 17:18:36 +0100 From: Petr Mladek To: Andrew Morton Subject: Re: [PATCH v3 4/4] printk/nmi: Increase the size of NMI buffer and make it configurable Message-ID: <20151218161836.GL3729@pathway.suse.cz> References: <1449667265-17525-1-git-send-email-pmladek@suse.com> <1449667265-17525-5-git-send-email-pmladek@suse.com> <20151211124159.GB3729@pathway.suse.cz> <20151211145725.b0e81bb4bb18fcd72ef5f557@linux-foundation.org> <20151211232113.GZ8644@n2100.arm.linux.org.uk> <20151211153054.48da5d4139b93dd4ed438f4c@linux-foundation.org> <20151215142621.GE3729@pathway.suse.cz> <20151217143858.447b5fe79aaa5ed7b2328d67@linux-foundation.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20151217143858.447b5fe79aaa5ed7b2328d67@linux-foundation.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20151218_081901_013653_F7E75DE6 X-CRM114-Status: GOOD ( 25.84 ) X-Spam-Score: -2.6 (--) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Linux MIPS Mailing List , Daniel Thompson , Russell King - ARM Linux , Cris , linux-s390 , Peter Zijlstra , the arch/x86 maintainers , "linux-kernel@vger.kernel.org" , Steven Rostedt , "adi-buildroot-devel@lists.sourceforge.net" , Ingo Molnar , Geert Uytterhoeven , Linux-sh list , sparclinux , Jiri Kosina , Thomas Gleixner , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Thu 2015-12-17 14:38:58, Andrew Morton wrote: > On Tue, 15 Dec 2015 15:26:21 +0100 Petr Mladek wrote: > > > > OK, thanks. So "not needed at present, might be needed in the future, > > > useful for out-of-tree debug code"? > > > > It is possible that I got it a wrong way on arm. The NMI buffer is > > usable there on two locations. > > > > First, the temporary is currently used to handle IPI_CPU_BACKTRACE. > > It seems that it is not a real NMI. But it seems to be available > > (compiled) on all arm system. This is why I introduced NEED_PRINTK_NMI > > Kconfig flag to avoid confusion with a real NMI. > > > > Second, there is the FIQ "NMI" handler that is called from > > /arch/arm/kernel/entry-armv.S. It is compiled only if _not_ > > defined $(CONFIG_CPU_V7M). It calls nmi_enter() and nmi_stop(). > > It looks like a real NMI handler. This is why I defined HAVE_NMI > > if (!CPU_V7M). > > > > A solution would be to define HAVE_NMI on all Arm systems and get rid > > of NEED_PRINTK_NMI. If you think that it would cause less confusion... > > So does this mean that the patch will be updated? Please, find the follow up patch below. I guess that you will want to squash it into the [1/n] one. From 144d90ada2e34b8807efcc01922c48d7c09797e7 Mon Sep 17 00:00:00 2001 From: Petr Mladek Date: Fri, 18 Dec 2015 16:04:35 +0100 Subject: [PATCH] printk/nmi: Remove the questionable CONFIG_NEED_PRINTK_NMI The flag NEED_PRINTK_NMI was added because of Arm. It used the NMI safe backtrace implementation on all Arm systems. But it did not have a real NMI handling on CPU_V7M. It seems that it causes more confusion than good. Let's use HAVE_NMI on all arm systems and get rid of the problematic flag. Signed-off-by: Petr Mladek --- arch/Kconfig | 3 --- arch/arm/Kconfig | 3 +-- init/Kconfig | 2 +- 3 files changed, 2 insertions(+), 6 deletions(-) diff --git a/arch/Kconfig b/arch/Kconfig index 7ce5101c2472..d1a18b313624 100644 --- a/arch/Kconfig +++ b/arch/Kconfig @@ -190,9 +190,6 @@ config HAVE_KPROBES_ON_FTRACE config HAVE_NMI bool -config NEED_PRINTK_NMI - bool - config HAVE_NMI_WATCHDOG depends on HAVE_NMI bool diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 96d2c275f0f7..01dc56d8f31b 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -63,8 +63,7 @@ config ARM select HAVE_KRETPROBES if (HAVE_KPROBES) select HAVE_MEMBLOCK select HAVE_MOD_ARCH_SPECIFIC - select HAVE_NMI if (!CPU_V7M) - select NEED_PRINTK_NMI if (CPU_V7M) + select HAVE_NMI select HAVE_OPROFILE if (HAVE_PERF_EVENTS) select HAVE_OPTPROBES if !THUMB2_KERNEL select HAVE_PERF_EVENTS diff --git a/init/Kconfig b/init/Kconfig index 61cfd96a3c96..abf79f3b1a55 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1481,7 +1481,7 @@ config PRINTK config PRINTK_NMI def_bool y depends on PRINTK - depends on HAVE_NMI || NEED_PRINTK_NMI + depends on HAVE_NMI config BUG bool "BUG() support" if EXPERT