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Date: Thu, 12 Nov 2020 12:40:36 +0100 From: Björn Töpel <bjorn.topel@...il.com> To: netdev@...r.kernel.org, bpf@...r.kernel.org Cc: Björn Töpel <bjorn.topel@...el.com>, magnus.karlsson@...el.com, ast@...nel.org, daniel@...earbox.net, maciej.fijalkowski@...el.com, sridhar.samudrala@...el.com, jesse.brandeburg@...el.com, qi.z.zhang@...el.com, kuba@...nel.org, edumazet@...gle.com, jonathan.lemon@...il.com, maximmi@...dia.com Subject: [PATCH bpf-next 4/9] xsk: check need wakeup flag in sendmsg() From: Björn Töpel <bjorn.topel@...el.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@...el.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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