Eric Dumazet wrote:
Eric Dumazet a écrit :
Patrick McHardy a écrit :
That looks more complicated since it requires to take multiple locks
occasionally (f.i. hash insertion, potentially helper-related and
expectation-related stuff), and there is the unconfirmed_list, where
fine-grained locking can't really be used without changing it to
a hash.
Yes its more complicated, but look what we did in 2.6.29 for tcp/udp
sockets, using RCU to have lockless lookups.
Yes, we still take a lock when doing an insert or delete at socket
bind/unbind time.
We could keep a central nf_conntrack_lock to guard insertions/deletes
from hash and unconfirmed_list.
But *normal* packets that only need to change state of one particular
connection could use RCU (without spinlock) to locate the conntrack,
then lock the found conntrack to perform all state changes.
Well... RCU is already used by conntrack :)
Maybe only __nf_ct_refresh_acct() needs not taking nf_conntrack_lock
The lock is currently used to avoid timer update races.
Martin has two old patches two remove it, but they require
changes to the timer code to support a mod_timer variant
that doesn't enable an inactive timer:
http://people.netfilter.org/gandalf/performance/patches/mod_timer_noact
http://people.netfilter.org/gandalf/performance/patches/__nf_ct_refresh_acct-locking
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