From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sai Prakash Ranjan Subject: Re: Crash in msm serial on dragonboard with ftrace bootargs Date: Tue, 16 Oct 2018 23:35:00 +0530 Message-ID: <472db11e-49a6-a1ee-e298-791ee1bbb10b@codeaurora.org> References: <1cae8f10-55f5-20ce-9105-30af6f88bd6e@codeaurora.org> <20181016112928.4b52afb5@gandalf.local.home> <8c2fb318-813d-81f1-1e2f-cdbc68353077@codeaurora.org> <20181016125721.236ada82@gandalf.local.home> <20181016134803.1b9260c1@gandalf.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20181016134803.1b9260c1@gandalf.local.home> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Steven Rostedt Cc: Stephen Boyd , Bjorn Andersson , Andy Gross , David Brown , Jiri Slaby , "Ivan T. Ivanov" , Kees Cook , "Joel Fernandes (Google)" , Geliang Tang , Greg Kroah-Hartman , Pramod Gurav , linux-arm-msm@vger.kernel.org, linux-soc@vger.kernel.org, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Rajendra Nayak , Vivek Gautam , Sibi Sankar List-Id: linux-arm-msm@vger.kernel.org On 10/16/2018 11:18 PM, Steven Rostedt wrote: > On Tue, 16 Oct 2018 23:06:24 +0530 > Sai Prakash Ranjan wrote: > >> On 10/16/2018 10:27 PM, Steven Rostedt wrote: >>> >>> OK, can you add to the command line: >>> >>> ftrace=function ftrace_filter=*schedule* >>> >>> to see if it's a specific function that may be causing the issue (but >>> hopefully it's not one of the scheduling functions that caused it). >>> >> >> Target boots fine with this. So its not scheduling functions that is >> causing it. Also I tried with ftrace_filter=*msm* just to be sure if >> tracing driver functions is causing any issue but its NOT. > > OK, seems that something is being traced that shouldn't be. > > When this happens after boot up, it's easy to bisect down to the > problem function. But since it's at boot up, it will take a lot longer. > > I would suggest to start by going down the alphabet. > > ftrace_filter=a* > ftrace_filter=b* > ftrace_filter=c* > [...] > > And at least find the letter the bad function starts with. > > Note, it could be more than one function (I've had that a couple of > times), and to find that out, you can test with "ftrace_notrace". Say > you find that the problem function starts with 'x'. You can do: > > ftrace_notrace=x* > > Which will trace all functions except those that start with an 'x', to > make sure it still boots. > > Remember, you still need to have ftrace=function for all of this. > > Once you find the letter of the function, you can try the next letter, > or perhaps come up with another method. I would say look at the > functions in /sys/kernel/debug/tracing/available_filter_functions, but > they don't list the init function (that can be traced). But you can > use /proc/kallsyms instead. > Ok got it, this sounds fun. I'll give it a try. Thanks -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation