From: Lai Jiangshan <laijs@cn.fujitsu.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Miller <davem@davemloft.net>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
netdev <netdev@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH net-next-2.6] fasync: RCU locking
Date: Wed, 14 Apr 2010 16:36:13 +0800 [thread overview]
Message-ID: <4BC57E7D.9060706@cn.fujitsu.com> (raw)
In-Reply-To: <1271230961.16881.630.camel@edumazet-laptop>
Eric Dumazet wrote:
> -void __kill_fasync(struct fasync_struct *fa, int sig, int band)
> +/*
> + * rcu_read_lock() is held
> + */
> +static void kill_fasync_rcu(struct fasync_struct *fa, int sig, int band)
> {
> while (fa) {
> struct fown_struct * fown;
> @@ -719,22 +728,19 @@ void __kill_fasync(struct fasync_struct *fa, int sig, int band)
> mechanism. */
> if (!(sig == SIGURG && fown->signum == 0))
> send_sigio(fown, fa->fa_fd, band);
> - fa = fa->fa_next;
> + fa = rcu_dereference(fa->fa_next);
> }
> }
>
Since rcu_read_lock() protects fasync_struct *fa for us, we can access
to @fa safely even fasync_remove_entry() is just called.
But this patch does not ensure 'fa->fa_file is not freed' nor
'fa->fa_fd is not released', so kill_fasync_rcu() may do wrong thing
if there is no other code ensure it.
next prev parent reply other threads:[~2010-04-14 8:36 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-14 7:42 [PATCH net-next-2.6] fasync: RCU locking Eric Dumazet
2010-04-14 8:36 ` Lai Jiangshan [this message]
2010-04-14 14:57 ` Eric Dumazet
2010-04-14 15:34 ` Eric Dumazet
2010-04-14 19:55 ` [PATCH net-next-2.6 v3] fasync: RCU and fine grained locking Eric Dumazet
2010-04-21 23:20 ` David Miller
2010-04-14 15:41 ` [PATCH net-next-2.6] fasync: RCU locking Paul E. McKenney
2010-04-21 23:19 ` David Miller
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