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authorDaniel Borkmann <dborkman@redhat.com>2014-04-08 17:26:13 +0200
committerDavid S. Miller <davem@davemloft.net>2014-04-08 13:06:07 -0400
commit52c35befb69b005c3fc5afdaae3a5717ad013411 (patch)
treecc9680dc2114afdf2c5aeea5553ca862712b979b /net/sctp
parent7563487cbf865284dcd35e9ef5a95380da046737 (diff)
downloadlinux-52c35befb69b005c3fc5afdaae3a5717ad013411.tar.bz2
net: sctp: wake up all assocs if sndbuf policy is per socket
SCTP charges chunks for wmem accounting via skb->truesize in sctp_set_owner_w(), and sctp_wfree() respectively as the reverse operation. If a sender runs out of wmem, it needs to wait via sctp_wait_for_sndbuf(), and gets woken up by a call to __sctp_write_space() mostly via sctp_wfree(). __sctp_write_space() is being called per association. Although we assign sk->sk_write_space() to sctp_write_space(), which is then being done per socket, it is only used if send space is increased per socket option (SO_SNDBUF), as SOCK_USE_WRITE_QUEUE is set and therefore not invoked in sock_wfree(). Commit 4c3a5bdae293 ("sctp: Don't charge for data in sndbuf again when transmitting packet") fixed an issue where in case sctp_packet_transmit() manages to queue up more than sndbuf bytes, sctp_wait_for_sndbuf() will never be woken up again unless it is interrupted by a signal. However, a still remaining issue is that if net.sctp.sndbuf_policy=0, that is accounting per socket, and one-to-many sockets are in use, the reclaimed write space from sctp_wfree() is 'unfairly' handed back on the server to the association that is the lucky one to be woken up again via __sctp_write_space(), while the remaining associations are never be woken up again (unless by a signal). The effect disappears with net.sctp.sndbuf_policy=1, that is wmem accounting per association, as it guarantees a fair share of wmem among associations. Therefore, if we have reclaimed memory in case of per socket accounting, wake all related associations to a socket in a fair manner, that is, traverse the socket association list starting from the current neighbour of the association and issue a __sctp_write_space() to everyone until we end up waking ourselves. This guarantees that no association is preferred over another and even if more associations are taken into the one-to-many session, all receivers will get messages from the server and are not stalled forever on high load. This setting still leaves the advantage of per socket accounting in touch as an association can still use up global limits if unused by others. Fixes: 4eb701dfc618 ("[SCTP] Fix SCTP sendbuffer accouting.") Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Cc: Thomas Graf <tgraf@suug.ch> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: Vlad Yasevich <vyasevic@redhat.com> Acked-by: Vlad Yasevich <vyasevic@redhat.com> Acked-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sctp')
-rw-r--r--net/sctp/socket.c36
1 files changed, 35 insertions, 1 deletions
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 981aaf8b6ace..5f83a6a2fa67 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -6593,6 +6593,40 @@ static void __sctp_write_space(struct sctp_association *asoc)
}
}
+static void sctp_wake_up_waiters(struct sock *sk,
+ struct sctp_association *asoc)
+{
+ struct sctp_association *tmp = asoc;
+
+ /* We do accounting for the sndbuf space per association,
+ * so we only need to wake our own association.
+ */
+ if (asoc->ep->sndbuf_policy)
+ return __sctp_write_space(asoc);
+
+ /* Accounting for the sndbuf space is per socket, so we
+ * need to wake up others, try to be fair and in case of
+ * other associations, let them have a go first instead
+ * of just doing a sctp_write_space() call.
+ *
+ * Note that we reach sctp_wake_up_waiters() only when
+ * associations free up queued chunks, thus we are under
+ * lock and the list of associations on a socket is
+ * guaranteed not to change.
+ */
+ for (tmp = list_next_entry(tmp, asocs); 1;
+ tmp = list_next_entry(tmp, asocs)) {
+ /* Manually skip the head element. */
+ if (&tmp->asocs == &((sctp_sk(sk))->ep->asocs))
+ continue;
+ /* Wake up association. */
+ __sctp_write_space(tmp);
+ /* We've reached the end. */
+ if (tmp == asoc)
+ break;
+ }
+}
+
/* Do accounting for the sndbuf space.
* Decrement the used sndbuf space of the corresponding association by the
* data size which was just transmitted(freed).
@@ -6620,7 +6654,7 @@ static void sctp_wfree(struct sk_buff *skb)
sk_mem_uncharge(sk, skb->truesize);
sock_wfree(skb);
- __sctp_write_space(asoc);
+ sctp_wake_up_waiters(sk, asoc);
sctp_association_put(asoc);
}