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	for linux-wireless@vger.kernel.org; Tue, 18 Oct 2011 12:07:45 +0200
Subject: Re: compat-wireless: backporting kfree_rcu()?
From: Johannes Berg <johannes@sipsolutions.net>
To: linux-wireless <linux-wireless@vger.kernel.org>
In-Reply-To: <1318925897.3958.11.camel@jlt3.sipsolutions.net> (sfid-20111018_101825_645167_3C966770)
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	 (sfid-20111018_101825_645167_3C966770)
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Date: Tue, 18 Oct 2011 12:07:41 +0200
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A complete different idea:

/* a larger rcu head struct */
struct compat_rcu_head {
	struct rcu_head rh; /* must be first */
	void *free_ptr;
};

/* define kfree_rcu */
extern void compat_free_rcu(struct rcu_head *rh);

#define kfree_rcu(ptr, head)	\
	do {
		(ptr)->head.free_ptr = ptr;
		call_rcu(&(ptr)->head.rh, compat_free_rcu);
	} while (0)

/* use it in all code */
#define rcu_head compat_rcu_head


and somewhere in a compat.ko file:

#undef rcu_head
void compat_free_rcu(struct rcu_head *rh)
{
	struct compat_rcu_head *crh = (void *)rh;
	kfree(crh->free_ptr);
}


thoughts?

johannes