Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754938AbZJSKRB (ORCPT ); Mon, 19 Oct 2009 06:17:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752914AbZJSKRA (ORCPT ); Mon, 19 Oct 2009 06:17:00 -0400 Received: from aa002msb.fastweb.it ([85.18.95.81]:49227 "EHLO aa002msb.fastweb.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750846AbZJSKQ7 (ORCPT ); Mon, 19 Oct 2009 06:16:59 -0400 Message-ID: <4ADC3C92.3000709@evidence.eu.com> Date: Mon, 19 Oct 2009 12:16:50 +0200 From: Claudio Scordino User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Catalin Marinas CC: rmk@arm.linux.org.uk, linux-kernel@vger.kernel.org, kernel@arm.linux.org.uk Subject: [PATCH] Default setting of the ARM_UNWIND option References: <4AD73DA4.4050006@evidence.eu.com> <1255620333.10164.77.camel@pc1117.cambridge.arm.com> In-Reply-To: <1255620333.10164.77.camel@pc1117.cambridge.arm.com> Content-Type: multipart/mixed; boundary="------------060600090505070306050102" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3724 Lines: 105 This is a multi-part message in MIME format. --------------060600090505070306050102 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: 7bit [email cut-and-pasted from a private discussion...] >> moving from release 2.6.27 to release 2.6.32-rc4, my ARM board >> (derived from AT91SAM9623-EK) started hanging at the initial >> "Calibrating delay loop" message. >> >> After some inspection, I found out the problem to be with commit >> adf8b37bafc1495393201a2ae4235846371870d0. >> >> In practice, it enables stack unwinding support by default. However, if >> enabled, it hangs my machine. >> >> The problem might be with my compiler (according to the help, stack >> unwinding only works with EABI compilers). >> >> I'm using a CodeSourcery gcc 4.2.1 "arm-none-linux-gnueabi". >> > > I think 4.2.1 generates really buggy code with -fno-frame-pointer, > nothing to do with the stack unwinding implementation in the kernel. I > would recommend you either use a newer compiler or disables ARM_UNWIND > in your .config (which automatically re-enables FRAMEPOINTER). > Hi Catalin, thank you for your answer. In my opinion, we should change the default setting of this option. Having "yes" as default policy for ARM_UNWIND means that, by default, the kernel does not boot if a user has a buggy compiler (like me) and he/she doesn't explicitly disable the ARM_UNWIND option. Consider that people may not know that their problem is related to the ARM_UNWIND option. Therefore, they may waste time just bisecting to understand where their problem really is. Therefore, my suggestion is to change the default policy of this option as shown in the attached patch, to avoid a potential waste of time of developers. Users who know that they can enable this option, will enable it. Let me know what you think about this suggestion. Many thanks and my best regards, Claudio --------------060600090505070306050102 Content-Type: text/x-patch; name="0001-Disable-stack-unwinding-support-by-default-since-it.patch" Content-Transfer-Encoding: 7bit Content-Disposition: inline; filename*0="0001-Disable-stack-unwinding-support-by-default-since-it.pat"; filename*1="ch" From: Claudio Scordino Date: Mon, 19 Oct 2009 11:59:16 +0200 Subject: [PATCH 1/1] Disable stack unwinding support by default, since it does not work on some buggy or not-EABI compilers. Disable stack unwinding support by default, since it does not work on some buggy or not-EABI compilers. Signed-off-by: Claudio Scordino --- arch/arm/Kconfig.debug | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug index 1a6f70e..925e3fd 100644 --- a/arch/arm/Kconfig.debug +++ b/arch/arm/Kconfig.debug @@ -19,13 +19,13 @@ config FRAME_POINTER config ARM_UNWIND bool "Enable stack unwinding support" depends on AEABI && EXPERIMENTAL - default y + default n help This option enables stack unwinding support in the kernel using the information automatically generated by the compiler. The resulting kernel image is slightly bigger but the performance is not affected. Currently, this feature - only works with EABI compilers. If unsure say Y. + only works with EABI compilers. If unsure say N. config DEBUG_USER bool "Verbose user fault messages" -- 1.6.0.4 --------------060600090505070306050102-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/