linux-kernel - Re: [PATCH] Linux Kernel GDB tracepoint module 2011-02-05

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Message-ID: <AANLkTinMx8mJYiDps3TuuaA1B4NLHi-PuCKm2=sTqyR0@mail.gmail.com>
Date:	Tue, 8 Feb 2011 21:23:52 +0800
From:	Hui Zhu <teawater@...il.com>
To:	Tom Tromey <tromey@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Michael Snyder <msnyder@...are.com>,
	Marc Khouzam <marc.khouzam@...csson.com>,
	Thiago Jung Bauermann <thiago.bauermann@...il.com>,
	Steven <mqyoung@...il.com>, colyli@...il.com,
	Christoph Hellwig <hch@...radead.org>,
	"gdb@...rceware.org" <gdb@...rceware.org>
Subject: Re: [PATCH] Linux Kernel GDB tracepoint module 2011-02-05

On Tue, Feb 8, 2011 at 00:25, Tom Tromey <tromey@...hat.com> wrote:
>>>>>> ">" == Hui Zhu <teawater@...il.com> writes:
>
>>> We have trouble for this printf is GDB is still not accept the patch
>>> that make tracepoint support printf, So if you want use it, you need
>>> patch the patch in
>>> http://sourceware.org/ml/gdb-patches/2011-02/msg00063.html and build
>>> your GDB with yourself.
>
> Thanks, I think this example was helpful.
>
>>> Sometimes, GDB will output some value like:
>>> inode has been optimized out of existence.
>>> res has been optimized out of existence.
>>> That is because value of inode and res is optimized. Linux Kernel is
>>> built with -O2 so you will get this trouble sometimes. If you do not
>>> care about the speed when you debug the Kernel, you can use the patch
>>> for Linux Kernel in
>
> I am curious to know what version of GCC you are using.  IME, the VTA
> patches really helped with this problem a lot -- though not completely.
> If you are not using a VTA-enabled GCC, you should.  And if you are, I
> think bug reports about values that are still optimized out would be
> useful.

My gcc is 4.4.5.  Does it have VTA?
Use the patch is easier than update gcc sometimes, right?  :)

BTW does VTA can handle the issue that after -O2 a lot of code
execution order is worong?
It affect me when I debug the Linux Kernel in qemu.

Thanks,
Hui
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