linux-kernel - [Slightly off topic] A question about R/B trees.

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Message-ID: <48F904FA.6090102@gmail.com>
Date:	Fri, 17 Oct 2008 23:34:50 +0200
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	linux-kernel@...r.kernel.org
Subject: [Slightly off topic] A question about R/B trees.

Hi,

I am working on my small project, and I need a fast container to hold a large sparse array.
Balanced trees seem to fit perfectly.

I decided to implement a red/black tree, and took a look at kernel rb tree for reference,
and I noticed that tree item has no parent pointer, while it seems that it should have it.

I know now that it has parent pointer, but it is mixed with current and parent node colour.
Thus it is assumed that last two bits of this pointer are zero.

I can see anywhere that this restriction is applied.
I see that structure is "aligned" but that I think only ensures that compiler places it
aligned in static data, does the alignment ensures that it will always place it on aligned address in a structure?
But then, the whole container structure can be misaligned, can't it?

Besides a comment there states that alignment is only for CRIS

How about a check for misalignment?

Best regards,
	Maxim Levitsky
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