linux-kernel - Re: [PATCH] [1/9] Add rcustring ADT for RCU protected strings v2

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Message-ID: <20100105141146.GD6836@linux.vnet.ibm.com>
Date:	Tue, 5 Jan 2010 06:11:46 -0800
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	ebiederm@...ssion.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [1/9] Add rcustring ADT for RCU protected strings v2

On Tue, Jan 05, 2010 at 11:47:46AM +0100, Andi Kleen wrote:
> On Mon, Jan 04, 2010 at 09:32:52PM -0800, Paul E. McKenney wrote:
> > > +/*
> > > + * Get a local private copy of a RCU protected string.
> > > + * Mostly useful to get a string that is stable while sleeping.
> > > + * Caller must free returned string.
> > > + */
> > > +char *access_rcu_string(char **str, int size, gfp_t gfp)
> > > +{
> > > +	char *copy = kmalloc(size, gfp);
> > > +	if (!str)
> > > +		return NULL;
> > > +	rcu_read_lock();
> > > +	strlcpy(copy, rcu_dereference(*str), size);
> > 
> > What if "str" is non-NULL, but "*str" is NULL?  Or is that disallowed
> > somehow?
> 
> I would consider it disallowed, all the strings have some default value.
> Empty string would be ""
> 
> If we allowed it the caller couldn't easily distingush error from expected NULL.

OK, then:

Reviewed-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

							Thanx, Paul
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