netdev - Re: [PATCH v2] net/sock: Update sk rcu iterator macro.

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Date:   Mon, 23 Oct 2017 18:42:50 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     Tim Hansen <devtimhansen@...il.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] net/sock: Update sk rcu iterator macro.

On Mon, Oct 23, 2017 at 11:39:22AM -0400, Tim Hansen wrote:
>Mark hlist nodes in sk rcu iterator as protected by the rcu.
>hlist_next_rcu accomplishes this and silences the warnings
>sparse throws for net/ipv4/udp.c and net/ipv6/udp.c.
>
>Found with make C=1 net/ipv4/udp.o on linux-next tag
>next-20171009.
>
>Signed-off-by: Tim Hansen <devtimhansen@...il.com>
>---
> include/net/sock.h | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
>diff --git a/include/net/sock.h b/include/net/sock.h
>index 64e5ac41b9cf..96cb7b7e4924 100644
>--- a/include/net/sock.h
>+++ b/include/net/sock.h
>@@ -737,10 +737,10 @@ static inline void sk_add_bind_node(struct sock *sk,
>  *
>  */
> #define sk_for_each_entry_offset_rcu(tpos, pos, head, offset)		       \
>-	for (pos = rcu_dereference((head)->first);			       \
>+	for (pos = rcu_dereference(hlist_next_rcu((head)->first));	       \

See below.

> 	     pos != NULL &&						       \
> 		({ tpos = (typeof(*tpos) *)((void *)pos - offset); 1;});       \
>-	     pos = rcu_dereference(pos->next))
>+	     pos = rcu_dereference(hlist_next_rcu(pos->next)))

This will return the next-next node instead of just the next one. You
probably want just hlist_next_rcu(pos) here.

-- 

Thanks,
Sasha