[Intel-wired-lan] [RFC PATCH bpf-next v2 4/9] xsk: check need wakeup flag in sendmsg()
Björn Töpel
bjorn.topel at gmail.com
Thu Nov 5 10:28:07 UTC 2020
From: Björn Töpel <bjorn.topel at intel.com>
Add a check for need wake up in sendmsg(), so that if a user calls
sendmsg() when no wakeup is needed, do not trigger a wakeup.
To simplify the need wakeup check in the syscall, unconditionally
enable the need wakeup flag for Tx. This has a side-effect for poll();
If poll() is called for a socket without enabled need wakeup, a Tx
wakeup is unconditionally performed.
The wakeup matrix for AF_XDP now looks like:
need wakeup | poll() | sendmsg() | recvmsg()
------------+--------------+-------------+------------
disabled | wake Tx | wake Tx | nop
enabled | check flag; | check flag; | check flag;
| wake Tx/Rx | wake Tx | wake Rx
Signed-off-by: Björn Töpel <bjorn.topel at intel.com>
---
net/xdp/xsk.c | 6 +++++-
net/xdp/xsk_buff_pool.c | 13 ++++++-------
2 files changed, 11 insertions(+), 8 deletions(-)
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 17d51d1a5752..2e5b9f27c7a3 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -465,13 +465,17 @@ static int xsk_sendmsg(struct socket *sock, struct msghdr *m, size_t total_len)
bool need_wait = !(m->msg_flags & MSG_DONTWAIT);
struct sock *sk = sock->sk;
struct xdp_sock *xs = xdp_sk(sk);
+ struct xsk_buff_pool *pool;
if (unlikely(!xsk_is_bound(xs)))
return -ENXIO;
if (unlikely(need_wait))
return -EOPNOTSUPP;
- return __xsk_sendmsg(sk);
+ pool = xs->pool;
+ if (pool->cached_need_wakeup & XDP_WAKEUP_TX)
+ return __xsk_sendmsg(sk);
+ return 0;
}
static int xsk_recvmsg(struct socket *sock, struct msghdr *m, size_t len, int flags)
diff --git a/net/xdp/xsk_buff_pool.c b/net/xdp/xsk_buff_pool.c
index 64c9e55d4d4e..a4acb5e9576f 100644
--- a/net/xdp/xsk_buff_pool.c
+++ b/net/xdp/xsk_buff_pool.c
@@ -144,14 +144,13 @@ static int __xp_assign_dev(struct xsk_buff_pool *pool,
if (err)
return err;
- if (flags & XDP_USE_NEED_WAKEUP) {
+ if (flags & XDP_USE_NEED_WAKEUP)
pool->uses_need_wakeup = true;
- /* Tx needs to be explicitly woken up the first time.
- * Also for supporting drivers that do not implement this
- * feature. They will always have to call sendto().
- */
- pool->cached_need_wakeup = XDP_WAKEUP_TX;
- }
+ /* Tx needs to be explicitly woken up the first time. Also
+ * for supporting drivers that do not implement this
+ * feature. They will always have to call sendto() or poll().
+ */
+ pool->cached_need_wakeup = XDP_WAKEUP_TX;
dev_hold(netdev);
--
2.27.0
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