From: Cong Wang <amwang@redhat.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev@vger.kernel.org,
Stephen Hemminger <stephen@networkplumber.org>,
"David S. Miller" <davem@davemloft.net>
Subject: Re: [Patch net-next v5 3/3] igmp: convert RTNL lock to a spinlock
Date: Sat, 15 Jun 2013 16:44:37 +0800 [thread overview]
Message-ID: <1371285877.23997.14.camel@cr0> (raw)
In-Reply-To: <1371284768.3252.151.camel@edumazet-glaptop>
On Sat, 2013-06-15 at 01:26 -0700, Eric Dumazet wrote:
> On Sat, 2013-06-15 at 16:12 +0800, Cong Wang wrote:
>
> > I _did_ try to replace spinlock with mutex, but apparently mutex_lock()
> > can't be called with rcu_read_lock() held, which is the case in
> > ip_mc_drop_socket().
> >
>
> If you hold a mutex, there is no need for rcu_read_lock() at all.
>
> Nobody can change the lists while you are the owner.
>
> We already have nice helpers, lockdep enabled.
>
> check rtnl_dereference() uses
>
>
Oops, I should mean to say ip_mc_leave_group(), not
ip_mc_drop_socket()...
The reason why it holds RCU is to get in_dev and still uses it after
spinlock is held, but I think we can fix ip_mc_find_dev() so that we can
call it without holding RCU outside, by taking a ref to in_dev?
Thanks!
prev parent reply other threads:[~2013-06-15 8:44 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-15 7:41 [Patch net-next v5 1/3] igmp: make some functions void Cong Wang
2013-06-15 7:41 ` [Patch net-next v5 2/3] ipv6,mcast: " Cong Wang
2013-06-15 7:41 ` [Patch net-next v5 3/3] igmp: convert RTNL lock to a spinlock Cong Wang
2013-06-15 7:55 ` Eric Dumazet
2013-06-15 8:12 ` Cong Wang
2013-06-15 8:26 ` Eric Dumazet
2013-06-15 8:44 ` Cong Wang [this message]
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