linux-kernel - Re: [PATCH 1/2] lib: add fast lzo decompressor

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Date:	Thu, 02 Apr 2009 14:30:10 +0200
From:	Andreas Robinson <andr345@...il.com>
To:	Nigel Cunningham <ncunningham@...a.org.au>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Alain Knaff <alain@...ff.lu>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] lib: add fast lzo decompressor

On Thu, 2009-04-02 at 10:40 +1100, Nigel Cunningham wrote:
> Sorry to jump in with a tangential issue, but I just noticed the
> thread
> and it reminded me of an issue :)
> 
> Should the lzo code used via cryptoapi (I believe it's the same stuff)
> be SMP safe? I've tried to use it work TuxOnIce and get image corruption
> (test kernel is 64 bit). The same code works fine if I tell it to use
> LZF (which comes with TuxOnIce), no compression or, IIRC, work single
> threaded.

Do you compress or decompress data through the crypto API?

Neither function modifies the input data and there are no static or
global variables in use, so there shouldn't be a problem there.

They do however modify the destination length argument.

But most importantly, each compressor thread needs a private work buffer
allocated through lzo_init() in crypto/lzo.c. So, if you use the crypto
API to compress and share the crypto_tfm struct among threads, that
would explain your breakage.

Cheers,
Andreas

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