From mboxrd@z Thu Jan  1 00:00:00 1970
From: "David S. Miller" <davem@davemloft.net>
Subject: Re: [patch] ipv4: initialize arp_tbl rw lock
Date: Sat, 15 Apr 2006 00:34:57 -0700 (PDT)
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From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Sat, 15 Apr 2006 09:27:45 +0200

> Tried to figure out what is causing the delays I experienced when I replaced
> module_init() in af_inet.c with fs_initcall(). After all it turned out that
> synchronize_net() which is basicically nothing else than synchronize_rcu()
> sometimes takes several seconds to complete?! No idea why that is...
> 
> callchain: inet_init() -> inet_register_protosw() -> synchronize_net()

The problem can't be rcu_init(), that gets done very early
in init/main.c

Maybe it's some timer or something else specific to s390?

It could also be that there's perhaps nothing to context
switch to, thus the RCU takes forever to "happen".