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

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Message-ID: <20100105104746.GB1778@basil.fritz.box>
Date:	Tue, 5 Jan 2010 11:47:46 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Andi Kleen <andi@...stfloor.org>, 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 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.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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