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[73.93.215.6]) by smtp.gmail.com with ESMTPSA id q27sm23035807pfd.14.2018.01.25.13.49.02 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 Jan 2018 13:49:03 -0800 (PST) Subject: Re: [RFC PATCH v2 0/1] of: easier debugging for node life cycle issues To: Wolfram Sang Cc: Steven Rostedt , devicetree@vger.kernel.org, Tyrel Datwyler , Geert Uytterhoeven , linux-renesas-soc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, Rob Herring , linux-kernel@vger.kernel.org References: <20180121143117.19805-1-wsa+renesas@sang-engineering.com> <00fc90ee-de26-f819-9c81-27d06918564d@gmail.com> <20180125060330.781667e9@vmware.local.home> From: Frank Rowand Message-ID: Date: Thu, 25 Jan 2018 13:49:01 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0 MIME-Version: 1.0 In-Reply-To: <20180125060330.781667e9@vmware.local.home> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Wolfram, On 01/25/18 03:03, Steven Rostedt wrote: > On Wed, 24 Jan 2018 22:55:13 -0800 > Frank Rowand wrote: > >> Hi Steve, > >> >> Off the top of your head, can you tell me know early in the boot >> process a trace_event can be called and successfully provide the >> data to someone trying to debug early boot issues? > > The trace events are enabled by early_initcall(). < snip > This means that ftrace can not be used for the of_node_get(), of_node_put(), and of_node_release() debug info, because these functions are called before early_initcall(). Please use pr_debug() for these functions. As far as I know, the of_reconfig_notify() could remain an ftrace instrumented function. But now that the only thing that would be ftrace instrumented is of_reconfig_notify(), I don't see a strong justification for changing the existing pr_debug() calls to an ftrace alternative. Though I suspect the original author of the patch still might desire to have the "#ifdef DEBUG" surrounding the pr_debug() calls removed since one of his issues was having to recompile his kernel to do his debugging. -Frank