Denis V. Lunev wrote:
Daniel Lezcano wrote:
From: Daniel Lezcano <[EMAIL PROTECTED]>
Denis Lunev spotted that if we take a reference to the network namespace
with the timewait sockets, we will need to wait for their expiration to
have the network namespace freed. This is a waste of time, the timewait
sockets are for avoiding to receive a duplicate packet from the network,
if the network namespace is freed, the network stack is removed, so no
chance to receive any packets from the outside world.
This patchset remove/destroy the timewait sockets when the
network namespace is freed.
Signed-off-by: Daniel Lezcano <[EMAIL PROTECTED]>
---
net/ipv4/tcp.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
[...]
This place seems non-trival and broken for me :( May be I am wrong.
+ write_lock_bh(&head->lock);
+
+ sk_for_each_safe(sk, node, tmp, &head->twchain) {
+
+ tw = inet_twsk(sk);
+ if (tw->tw_net != net)
+ continue;
+
+ /* deschedule the timewait socket */
+ spin_lock(&tcp_death_row.death_lock);
+ if (inet_twsk_del_dead_node(tw)) {
+ inet_twsk_put(tw);
+ if (--tcp_death_row.tw_count == 0)
+ del_timer(&tcp_death_row.tw_timer);
There is a call inet_twsk_deschedule which do exactly what we need to
void inet_twsk_deschedule(struct inet_timewait_sock *tw,
struct inet_timewait_death_row *twdr)
{
spin_lock(&twdr->death_lock);
if (inet_twsk_del_dead_node(tw)) {
inet_twsk_put(tw);
if (--twdr->tw_count == 0)
del_timer(&twdr->tw_timer);
}
spin_unlock(&twdr->death_lock);
__inet_twsk_kill(tw, twdr->hashinfo);
}
and, from my point of view, your patch [2] is even not needed. We should do
restart:
write_lock_bh(&head->lock);
sk_for_each_safe(sk, node, tmp, &head->twchain) {
tw = inet_twsk(sk);
if (tw->tw_net != net)
continue;
sock_hold(sk);
write_unlock_bh(&head->lock);
inet_twsk_deschedule(tw, &tcp_death_row);
inet_twsk_put(tw);
goto restart;
}
This removes serious locking issue. You have introduced dependency
between write_lock_bh(&head->lock); and
spin_lock(&tcp_death_row.death_lock);
This should be at least checked and documented in the headers. I am not
sure that this is correct.
If my approach is correct, your second patch is not needed.
It will also worth to local_bh_enable() at the very beginning and remove
_bh from write_lock.
local_bh_disable / local_bh_enable at the very beginning ?
like that ?
-------------
local_bh_disable();
/* Browse the the established hash table */
for (h = 0; h < (tcp_hashinfo.ehash_size); h++) {
struct inet_ehash_bucket *head =
inet_ehash_bucket(&tcp_hashinfo, h);
restart:
write_lock(&head->lock);
sk_for_each_safe(sk, node, tmp, &head->twchain) {
tw = inet_twsk(sk);
if (tw->tw_net != net)
continue;
sock_hold(sk);
write_unlock(&head->lock);
inet_twsk_deschedule(tw, &tcp_death_row);
inet_twsk_put(tw);
goto restart;
}
}
local_bh_enable();
-------------
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