From: Arnd Bergmann <arnd@arndb•de>
To: paulmck@linux•vnet.ibm.com
Cc: Herbert Xu <herbert@gondor•apana.org.au>,
"David S. Miller" <davem@davemloft•net>,
netdev@vger•kernel.org, Stephen Hemminger <shemminger@vyatta•com>
Subject: Re: [PATCH 6/13] bridge: Add core IGMP snooping support
Date: Wed, 10 Mar 2010 10:41:32 +0100 [thread overview]
Message-ID: <201003101041.32518.arnd@arndb.de> (raw)
In-Reply-To: <20100310021410.GD6203@linux.vnet.ibm.com>
On Wednesday 10 March 2010 03:14:10 Paul E. McKenney wrote:
> On Tue, Mar 09, 2010 at 10:12:59PM +0100, Arnd Bergmann wrote:
>
> > I've just tried annotating net/ipv4/route.c like this and did not get
> > very far, because the same pointers are used for rcu and rcu_bh.
> > Could you check if this is a false positive or an actual finding?
>
> Hmmm... I am only seeing a call_rcu_bh() here, so unless I am missing
> something, this is a real problem in TREE_PREEMPT_RCU kernels. The
> call_rcu_bh() only interacts with the rcu_read_lock_bh() readers, not
> the rcu_read_lock() readers.
>
> One approach is to run freed blocks through both types of grace periods,
> I suppose.
Well, if I introduce different __rcu and __rcu_bh address space annotations,
sparse would still not like that, because then you can only pass the annotated
pointers into either rcu_dereference or rcu_dereference_bh.
What the code seems to be doing here is in some places
local_bh_disable();
...
rcu_read_lock();
rcu_dereference(rt_hash_table[h].chain);
rcu_read_unlock();
...
local_bh_enable();
and in others
rcu_read_lock_bh();
rcu_dereference_bh(rt_hash_table[h].chain);
rcu_read_unlock_bh();
When rt_hash_table[h].chain gets the __rcu_bh annotation, we'd have to
turn first rcu_dereference into rcu_dereference_bh in order to have a clean
build with sparse. Would that change be
a) correct from RCU perspective,
b) desirable for code inspection, and
c) lockdep-clean?
Arnd
next prev parent reply other threads:[~2010-03-10 9:42 UTC|newest]
Thread overview: 81+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-26 15:34 [RFC] [1/13] bridge: Add IGMP snooping support Herbert Xu
2010-02-26 15:35 ` [PATCH 1/13] bridge: Do br_pass_frame_up after other ports Herbert Xu
2010-02-26 15:35 ` [PATCH 2/13] bridge: Allow tail-call on br_pass_frame_up Herbert Xu
2010-02-27 11:14 ` David Miller
2010-02-27 15:36 ` Herbert Xu
2010-02-26 15:35 ` [PATCH 3/13] bridge: Avoid unnecessary clone on forward path Herbert Xu
2010-02-26 15:35 ` [PATCH 4/13] bridge: Use BR_INPUT_SKB_CB on xmit path Herbert Xu
2010-02-26 15:35 ` [PATCH 5/13] bridge: Split may_deliver/deliver_clone out of br_flood Herbert Xu
2010-02-26 15:35 ` [PATCH 6/13] bridge: Add core IGMP snooping support Herbert Xu
2010-02-26 15:35 ` [PATCH 7/13] bridge: Add multicast forwarding functions Herbert Xu
2010-02-26 15:35 ` [PATCH 8/13] bridge: Add multicast start/stop hooks Herbert Xu
2010-02-26 15:35 ` [PATCH 9/13] bridge: Add multicast data-path hooks Herbert Xu
2010-02-26 15:35 ` [PATCH 10/13] bridge: Add multicast_router sysfs entries Herbert Xu
2010-02-27 0:42 ` Stephen Hemminger
2010-02-27 11:29 ` David Miller
2010-02-27 15:53 ` Herbert Xu
2010-03-09 12:25 ` Herbert Xu
2010-03-09 12:26 ` Herbert Xu
2010-02-26 15:35 ` [PATCH 11/13] bridge: Add multicast_snooping sysfs toggle Herbert Xu
2010-02-26 15:35 ` [PATCH 12/13] bridge: Add hash elasticity/max sysfs entries Herbert Xu
2010-02-26 15:35 ` [PATCH 13/13] bridge: Add multicast count/interval " Herbert Xu
2010-02-28 5:40 ` [1/13] bridge: Add IGMP snooping support Herbert Xu
2010-02-28 5:41 ` [PATCH 1/13] bridge: Do br_pass_frame_up after other ports Herbert Xu
2010-02-28 5:41 ` [PATCH 2/13] bridge: Allow tail-call on br_pass_frame_up Herbert Xu
2010-02-28 5:41 ` [PATCH 3/13] bridge: Avoid unnecessary clone on forward path Herbert Xu
2010-02-28 5:41 ` [PATCH 4/13] bridge: Use BR_INPUT_SKB_CB on xmit path Herbert Xu
2010-02-28 5:41 ` [PATCH 5/13] bridge: Split may_deliver/deliver_clone out of br_flood Herbert Xu
2010-02-28 5:41 ` [PATCH 6/13] bridge: Add core IGMP snooping support Herbert Xu
2010-03-05 23:43 ` Paul E. McKenney
2010-03-06 1:17 ` Herbert Xu
2010-03-06 5:06 ` Paul E. McKenney
2010-03-06 6:56 ` Herbert Xu
2010-03-06 7:03 ` Herbert Xu
2010-03-07 23:31 ` David Miller
2010-03-06 7:07 ` Herbert Xu
2010-03-07 23:31 ` David Miller
2010-03-06 15:00 ` Paul E. McKenney
2010-03-06 15:19 ` Paul E. McKenney
2010-03-06 19:00 ` Paul E. McKenney
2010-03-07 2:45 ` Herbert Xu
2010-03-07 3:11 ` Paul E. McKenney
2010-03-08 18:50 ` Arnd Bergmann
2010-03-09 3:15 ` Paul E. McKenney
2010-03-11 18:49 ` Arnd Bergmann
2010-03-14 23:01 ` Paul E. McKenney
2010-03-09 21:12 ` Arnd Bergmann
2010-03-10 2:14 ` Paul E. McKenney
2010-03-10 9:41 ` Arnd Bergmann [this message]
2010-03-10 10:39 ` Eric Dumazet
2010-03-10 10:49 ` Herbert Xu
2010-03-10 13:13 ` Paul E. McKenney
2010-03-10 14:07 ` Herbert Xu
2010-03-10 16:26 ` Paul E. McKenney
2010-03-10 16:35 ` David Miller
2010-03-10 17:56 ` Arnd Bergmann
2010-03-10 21:25 ` Paul E. McKenney
2010-03-10 13:27 ` Arnd Bergmann
2010-03-10 13:39 ` Arnd Bergmann
2010-03-10 13:19 ` Paul E. McKenney
2010-03-10 13:30 ` Arnd Bergmann
2010-03-10 13:57 ` Paul E. McKenney
2010-02-28 5:41 ` [PATCH 7/13] bridge: Add multicast forwarding functions Herbert Xu
2010-02-28 5:41 ` [PATCH 8/13] bridge: Add multicast start/stop hooks Herbert Xu
2010-02-28 5:41 ` [PATCH 9/13] bridge: Add multicast data-path hooks Herbert Xu
2010-04-27 17:13 ` [PATCH net-next] bridge: use is_multicast_ether_addr Stephen Hemminger
2010-04-27 19:53 ` David Miller
2010-02-28 5:41 ` [PATCH 10/13] bridge: Add multicast_router sysfs entries Herbert Xu
2010-04-27 17:13 ` [PATCH net-next] bridge: multicast router list manipulation Stephen Hemminger
2010-04-27 19:54 ` David Miller
2010-04-27 23:11 ` Michał Mirosław
2010-04-27 23:25 ` Stephen Hemminger
2010-04-27 23:28 ` David Miller
2010-04-27 23:44 ` Stephen Hemminger
2010-04-27 23:51 ` David Miller
2010-04-27 23:27 ` David Miller
2010-04-28 1:51 ` Herbert Xu
2010-02-28 5:41 ` [PATCH 11/13] bridge: Add multicast_snooping sysfs toggle Herbert Xu
2010-02-28 5:41 ` [PATCH 12/13] bridge: Add hash elasticity/max sysfs entries Herbert Xu
2010-02-28 5:41 ` [PATCH 13/13] bridge: Add multicast count/interval " Herbert Xu
2010-02-28 8:52 ` [1/13] bridge: Add IGMP snooping support David Miller
2010-03-01 2:08 ` Herbert Xu
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