tcp: prepare fastopen code for upcoming listener changes
While auditing TCP stack for upcoming 'lockless' listener changes,
I found I had to change fastopen_init_queue() to properly init the object
before publishing it.
Otherwise an other cpu could try to lock the spinlock before it gets
properly initialized.
Instead of adding appropriate barriers, just remove dynamic memory
allocations :
- Structure is 28 bytes on 64bit arches. Using additional 8 bytes
for holding a pointer seems overkill.
- Two listeners can share same cache line and performance would suffer.
If we really want to save few bytes, we would instead dynamically allocate
whole struct request_sock_queue in the future.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index db43c62..f69f436 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -142,9 +142,9 @@
if (!child)
return NULL;
- spin_lock(&queue->fastopenq->lock);
- queue->fastopenq->qlen++;
- spin_unlock(&queue->fastopenq->lock);
+ spin_lock(&queue->fastopenq.lock);
+ queue->fastopenq.qlen++;
+ spin_unlock(&queue->fastopenq.lock);
/* Initialize the child socket. Have to fix some values to take
* into account the child is a Fast Open socket and is created
@@ -237,8 +237,8 @@
* between qlen overflow causing Fast Open to be disabled
* temporarily vs a server not supporting Fast Open at all.
*/
- fastopenq = inet_csk(sk)->icsk_accept_queue.fastopenq;
- if (!fastopenq || fastopenq->max_qlen == 0)
+ fastopenq = &inet_csk(sk)->icsk_accept_queue.fastopenq;
+ if (fastopenq->max_qlen == 0)
return false;
if (fastopenq->qlen >= fastopenq->max_qlen) {