linux-kernel - Re: Leaks in trace reported by kmemleak

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Message-Id: <1256216968.8608.21.camel@pc1117.cambridge.arm.com>
Date:	Thu, 22 Oct 2009 14:09:28 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Zdenek Kabelac <zdenek.kabelac@...il.com>
Cc:	Li Zefan <lizf@...fujitsu.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: Leaks in trace reported by kmemleak

Hi Zdenek,

On Tue, 2009-10-20 at 11:58 +0200, Zdenek Kabelac wrote:
> I've tested your git with updates - and here is my experience:
> 
> I'm still able to get FP leaks printed even with the print of
> more-then-once appearanc.

I updated the kmemleak.git tree and in my tests it reduced the false
positives significantly. I dropped the two-pass scanning patch and I
added a new one which checks whether objects were modified since the
previous leak suspicion and only report them if unmodified (using
csum_partial for checksum calculation). This works well with linked
lists since list deletion modifies the prev/next pointers of those left
in the list (like in the debug_objects case).

> Also jiffies might be eventually more readable via data/time - but
> this can be preprocessed via script.

Jiffies is still useful to ensure it's the same object or a new one
allocated in the same function (and possibly false positive). I added
another bit of information - the age of an object in seconds.msecs.

-- 
Catalin

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