linux-kernel - Re: [PATCH v10 Golden] Unified trace buffer

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Message-ID: <20080929233539.GA31143@Krystal>
Date:	Mon, 29 Sep 2008 19:35:40 -0400
From:	Mathieu Desnoyers <compudj@...stal.dyndns.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	prasad@...ux.vnet.ibm.com,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	David Wilder <dwilder@...ibm.com>, hch@....de,
	Martin Bligh <mbligh@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Steven Rostedt <srostedt@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: Re: [PATCH v10 Golden] Unified trace buffer

* Steven Rostedt (rostedt@...dmis.org) wrote:
[...]
> +/*
> + * This hack stolen from mm/slob.c.
> + * We can store per page timing information in the page frame of the page.
> + * Thanks to Peter Zijlstra for suggesting this idea.
> + */
> +struct buffer_page {
> +	union {
> +		struct {
> +			unsigned long	 flags;		/* mandatory */
> +			atomic_t	 _count;	/* mandatory */
> +			u64		 time_stamp;	/* page time stamp */
> +			unsigned	 size;		/* size of page data */
> +			struct list_head list;		/* list of free pages */
> +		};
> +		struct page page;
> +	};
> +};
> +

Hi Steven,

You should have a look at mm/slob.c free_slob_page(). I think your page
free will generate a "bad_page" call due to mapping != NULL and mapcount
!= 0. I just ran into this in my own code. :)

Regards,

Mathieu

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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