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From: Arnd Bergmann <arnd@arndb.de>
To: Geoff Levand <geoffrey.levand@am.sony.com>
Subject: Re: [patch 3/3] PS3: Add logical performance monitor driver support
Date: Sun, 6 Jan 2008 22:56:17 +0100
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Cc: linuxppc-dev@ozlabs.org, paulus@samba.org,
	Takashi Yamamoto <Takashi02_Yamamoto@hq.scei.sony.co.jp>
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On Sunday 06 January 2008, Geoff Levand wrote:
> 
> > This mutex is documented as the 'open/close' mutex and you use it
> > to prevent concurrent execution of the open and close functions.
> > However, it's unclear what data structures are actually protected
> > by it.
> > 
> > I think this is the result of unusual lifetime rules for the lpm_priv
> > object, which I already mentioned above.
> 
> Yes, we really just need to use the mutex to allow only a single instance,
> and so do a mutex_trylock() in ps3_lpm_open() and return -EBUSY on fail,
> and then a mutex_unlock() in ps3_lpm_close().

A simple atomic_test_and_set in open() should do the job just as well then.

	Arnd <><