linux-kernel - Re: [PATCH 4/5] sctp: protocol.c call rcu

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Message-ID: <4A2E8357.80509@hp.com>
Date:	Tue, 09 Jun 2009 11:44:23 -0400
From:	Vlad Yasevich <vladislav.yasevich@...com>
To:	paulmck@...ux.vnet.ibm.com
CC:	Jesper Dangaard Brouer <hawk@...x.dk>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, urs.thuermann@...kswagen.de,
	oliver.hartkopp@...kswagen.de, wg@...ndegger.com, sri@...ibm.com,
	linux-sctp@...r.kernel.org, Trond.Myklebust@...app.com,
	linux-nfs@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH 4/5] sctp: protocol.c call rcu_barrier() on unload.

Paul E. McKenney wrote:
> On Mon, Jun 08, 2009 at 03:11:43PM +0200, Jesper Dangaard Brouer wrote:
>> On module unload call rcu_barrier(), this is needed as synchronize_rcu()
>> is not strong enough.  The kmem_cache_destroy() does invoke
>> synchronize_rcu() but it does not provide same protection.
> 
> Good, looks like sctp_v4_del_protocol() invokes call_rcu(), which the
> rcu_barrier() would then wait for.  And it looks like sctp_v6_del_protocol()
> does the same for IPv6.
> 
> Reviewed_by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> 
>> Signed-off-by: Jesper Dangaard Brouer <hawk@...x.dk>
>> ---
>>
>>  net/sctp/protocol.c |    2 ++
>>  1 files changed, 2 insertions(+), 0 deletions(-)
>>
>> diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
>> index cb2c50d..79cbd47 100644
>> --- a/net/sctp/protocol.c
>> +++ b/net/sctp/protocol.c
>> @@ -1370,6 +1370,8 @@ SCTP_STATIC __exit void sctp_exit(void)
>>  	sctp_proc_exit();
>>  	cleanup_sctp_mibs();
>>
>> +	rcu_barrier(); /* Wait for completion of call_rcu()'s */
>> +
>>  	kmem_cache_destroy(sctp_chunk_cachep);
>>  	kmem_cache_destroy(sctp_bucket_cachep);
>>  }
>>

Shouldn't the rcu_barrier call be before sctp_free_local_addr_list()?

-vlad
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