linux-kernel - Re: [PATCH perf/core 1/2] [RESEND] perf probe: Show the error reason comes from invalid DSO

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Message-ID: <5566566D.7030505@hitachi.com>
Date:	Thu, 28 May 2015 08:42:37 +0900
From:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
To:	Arnaldo Carvalho de Melo <acme@...nel.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Richard Weinberger <richard@....at>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>, namhyung@...nel.org,
	Jiri Olsa <jolsa@...hat.com>, Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH perf/core 1/2] [RESEND] perf probe: Show the error reason
 comes from invalid DSO

On 2015/05/27 21:50, Arnaldo Carvalho de Melo wrote:
> Em Wed, May 27, 2015 at 05:37:18PM +0900, Masami Hiramatsu escreveu:
>> Show the reason of error when dso__load* failed. This shows
>> when user gives wrong kernel image or wrong path.
>  
>> Without this, perf probe shows an obscure message.
>>   ----
>>   $ perf probe -k ~/kbin/linux-3.x86_64/vmlinux -L vfs_read
>>   Failed to find path of kernel module.
>>     Error: Failed to show lines.
>>   ----
>  
>> With this, perf shows appropriate error message.
>>   ----
>>   $ perf probe -k ~/kbin/linux-3.x86_64/vmlinux -L vfs_read
>>   Failed to find the path for kernel: Mismatching build id
>>     Error: Failed to show lines.
>>   ----
>> And
>>   ----
>>   $ perf probe -k /non-exist/kernel/vmlinux -L vfs_read
>>   Failed to find the path for kernel: No such file or directory
>>     Error: Failed to show lines.
>>   ----
> 
> Its better than before, and I am applying it.
> 
> But please consider to change the message further, because when one
> specifies the vmlinux file to use with -k/--vmlinux, the tool is not
> trying to "find the path for kernel", it is trying to use a specific
> vmlinux file.
> 
> I.e. the messages above are good if we do:
> 
>   perf probe -L vfs_read
> 
> Here it _will_ try to find the path, as none was given.
> 
> So, when -k/--vmlinux is used, I suggest that the message be:
> 
>   $ perf probe -k ~/kbin/linux-3.x86_64/vmlinux -L vfs_read
>   The kernel file "~/kbin/linux-3.x86_64/vmlinux" could not be used: Mismatching build id
>     Error: Failed to show lines.
> 
> And:
> 
>   $ perf probe -k /non-exist/kernel/vmlinux -L vfs_read
>   The kernel file "/non-exist/kernel/vmlinux" could not be used: No such file or directory
>     Error: Failed to show lines.

Indeed! This looks better for me.

Thank you!

-- 
Masami HIRAMATSU
Linux Technology Research Center, System Productivity Research Dept.
Center for Technology Innovation - Systems Engineering
Hitachi, Ltd., Research & Development Group
E-mail: masami.hiramatsu.pt@...achi.com
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