Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754407Ab0KHKm7 (ORCPT ); Mon, 8 Nov 2010 05:42:59 -0500 Received: from mail-iw0-f174.google.com ([209.85.214.174]:43530 "EHLO mail-iw0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754368Ab0KHKm6 convert rfc822-to-8bit (ORCPT ); Mon, 8 Nov 2010 05:42:58 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:sender:in-reply-to:references:date :x-google-sender-auth:message-id:subject:from:to:cc:content-type :content-transfer-encoding; b=JYlHS6LvFmTlshZ4vR9UXrXtmvHaCOi4p+0o+ZfOz+sTThcuLs9slHIBIuKQ6w3ZiH m5n630tH4PUKFvzZR/BO+WPvSaOSV11O9l5T34OcPrWkzG6GKzvhPK2+tkuRzLPgPuYN UduWzorOiufT0OK3FI0GwN2Q9VBp4mlonuX3I= MIME-Version: 1.0 In-Reply-To: <20101108091858.GP16938@pengutronix.de> References: <1289067954-5080-1-git-send-email-rabin@rab.in> <1289067954-5080-6-git-send-email-rabin@rab.in> <20101108091858.GP16938@pengutronix.de> Date: Mon, 8 Nov 2010 10:42:57 +0000 X-Google-Sender-Auth: sPcTvKh2VrG-lmmNllSH_TPomSY Message-ID: Subject: Re: [PATCH 6/6] ARM: ftrace: enable function graph tracer From: Catalin Marinas To: =?ISO-8859-1?Q?Uwe_Kleine=2DK=F6nig?= Cc: Rabin Vincent , Frederic Weisbecker , "linux-kernel@vger.kernel.org" , Steven Rostedt , "linux-arm-kernel@lists.infradead.org" , Tim Bird Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1941 Lines: 41 2010/11/8 Uwe Kleine-K?nig : > On Sat, Nov 06, 2010 at 07:06:28PM +0000, Catalin Marinas wrote: >> On Saturday, November 6, 2010, Rabin Vincent wrote: >> > Add the options to enable the function graph tracer on ARM. ?Function >> > graph tracer support requires frame pointers, so exclude Thumb-2 and >> > also explicitly select FRAME_POINTER in FUNCTION_GRAPH_TRACER since >> > FUNCTION_TRACER doesn't select FRAME_POINTER when ARM_UNWIND is used >> > Therefore, with GCC 4.4.0+, you get plain function tracing without frame >> > pointers, but you'll need them if you want function graph tracing. >> ..... >> > --- a/kernel/trace/Kconfig >> > +++ b/kernel/trace/Kconfig >> > @@ -141,6 +141,7 @@ config FUNCTION_TRACER >> > >> > ?config FUNCTION_GRAPH_TRACER >> > ?? ? ? ?bool "Kernel Function Graph Tracer" >> > + ? ? ? select FRAME_POINTER if ARM_UNWIND >> >> Would it be better to modify FRAME_POINTER definition in the ARM >> Kconfig so that it is enabled automatically when FUNCTION_GRAPH_TRACER >> is enabled? > I don't like that suggestion much because it hides the dependency. > Moreover a "default y if FUNCTION_GRAPH_TRACER" doesn't work if a > precondition for FRAME_POINTER isn't true. ?Rabin's approach at least > generates a warning. If a precondition for FRAME_POINTER isn't true, we should not force it via 'select'. We try to get rid of such warnings in the kernel. However, on ARM the FRAME_POINTER depends on !THUMB2_KERNEL but for Thumb-2 kernels HAVE_FUNCTION_GRAPH_TRACER is also disabled, so there isn't a dependency issue here. It's more like a personal preference to keep the changes within the arch/arm tree. -- Catalin -- 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/