Re: [PATCH 4/5] sctp: protocol.c call rcu_barrier() on unload.

Vlad Yasevich
2009-06-09T15:44:23Z

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@linux.vnet.ibm.com>
>
>> Signed-off-by: Jesper Dangaard Brouer <hawk@comx.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