netdev - Re: [net 1/1] tipc: fix cancellation of topology subscriptions

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Message-Id: <20190320.111733.684046665730660576.davem@davemloft.net>
Date:   Wed, 20 Mar 2019 11:17:33 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     jon.maloy@...csson.com
Cc:     netdev@...r.kernel.org, gordan.mihaljevic@...tech.com.au,
        tung.q.nguyen@...tech.com.au, hoang.h.le@...tech.com.au,
        canh.d.luu@...tech.com.au, ying.xue@...driver.com,
        tipc-discussion@...ts.sourceforge.net
Subject: Re: [net 1/1] tipc: fix cancellation of topology subscriptions

From: Jon Maloy <jon.maloy@...csson.com>
Date: Wed, 20 Mar 2019 10:59:03 +0100

> From: Erik Hugne <erik.hugne@...il.com>
> 
> When cancelling a subscription, we have to clear the cancel bit in the
> request before iterating over any established subscriptions with memcmp.
> Otherwise no subscription will ever be found, and it will not be
> possible to explicitly unsubscribe individual subscriptions.
 ...
> diff --git a/net/tipc/topsrv.c b/net/tipc/topsrv.c
> index 4a708a4..b05a89a 100644
> --- a/net/tipc/topsrv.c
> +++ b/net/tipc/topsrv.c
> @@ -363,6 +363,7 @@ static int tipc_conn_rcv_sub(struct tipc_topsrv *srv,
>  	struct tipc_subscription *sub;
>  
>  	if (tipc_sub_read(s, filter) & TIPC_SUB_CANCEL) {
> +		s->filter ^= __constant_ntohl(TIPC_SUB_CANCEL);
>  		tipc_conn_delete_sub(con, s);

It is confusing to say we have to "clear" some bit in a certain
situation and then use a xor operation which "inverts" a bit.

Please use "&= ~VAL" instead.

Thank you.