linux-kernel - Re: [PATCH 3/4] rhashtable: use bit_spin

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Date:   Tue, 26 Mar 2019 13:27:14 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     NeilBrown <neilb@...e.com>
Cc:     Thomas Graf <tgraf@...g.ch>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] rhashtable: use bit_spin_locks to protect hash
 bucket.

On Mon, Mar 25, 2019 at 04:05:39PM +1100, NeilBrown wrote:
>
> +/*
> + * If 'p' is a bucket head and might be locked:
> + *   rht_ptr() returns the address without the lock bit.
> + *   rht_ptr_locked() returns the address WITH the lock bit.
> + *   rht_is_locked() tests if the lock bit is set.
> + */
> +static inline struct rhash_head __rcu *rht_ptr(const struct rhash_head *p)
> +{
> +	return (void *)(((unsigned long)p) & ~2UL);
> +}

My preference would be to turn rhash_head * into an opaque type
that can only be dereferenced through rht_ptr.

Thanks,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt