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xsk: Check need wakeup flag in sendmsg() 

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@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Magnus Karlsson <magnus.karlsson@intel.com>
Link: https://lore.kernel.org/bpf/20201130185205.196029-5-bjorn.topel@gmail.com
This commit is contained in:
Björn Töpel 2020-11-30 19:51:59 +01:00 committed by Daniel Borkmann
parent 45a8668184
commit e392081837
2 changed files with 11 additions and 8 deletions
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6
net/xdp/xsk.c
View File

@ -522,13 +522,17 @@ 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)

13
net/xdp/xsk_buff_pool.c
View File

@ -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);