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

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Message-ID: <m3hbcfzu9u.fsf@fleche.redhat.com>
Date:	Mon, 07 Feb 2011 09:25:33 -0700
From:	Tom Tromey <tromey@...hat.com>
To:	Hui Zhu <teawater@...il.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\@sourceware.org" <gdb@...rceware.org>
Subject: Re: [PATCH] Linux Kernel GDB tracepoint module 2011-02-05

>>>>> ">" == 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.

Tom
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