[PATCH 5.15 172/177] Revert "xsk: Do not sleep in poll() when need_wakeup set"

Greg Kroah-Hartman
2021-12-20T15:20:42Z

From: Magnus Karlsson <magnus.karlsson@intel.com>

commit 0706a78f31c4217ca144f630063ec9561a21548d upstream.

This reverts commit bd0687c18e635b63233dc87f38058cd728802ab4.

This patch causes a Tx only workload to go to sleep even when it does
not have to, leading to misserable performance in skb mode. It fixed
one rare problem but created a much worse one, so this need to be
reverted while I try to craft a proper solution to the original
problem.

Fixes: bd0687c18e63 ("xsk: Do not sleep in poll() when need_wakeup set")
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20211217145646.26449-1-magnus.karlsson@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/xdp/xsk.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -692,6 +692,8 @@ static __poll_t xsk_poll(struct file *fi
struct xdp_sock *xs = xdp_sk(sk);
struct xsk_buff_pool *pool;

+ sock_poll_wait(file, sock, wait);
+
if (unlikely(!xsk_is_bound(xs)))
return mask;

@@ -703,8 +705,6 @@ static __poll_t xsk_poll(struct file *fi
else
/* Poll needs to drive Tx also in copy mode */
__xsk_sendmsg(sk);
- } else {
- sock_poll_wait(file, sock, wait);
}

if (xs->rx && !xskq_prod_is_empty(xs->rx))