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xsk: Do not sleep in poll() when need_wakeup set 

commit bd0687c18e635b63233dc87f38058cd728802ab4 upstream.

Do not sleep in poll() when the need_wakeup flag is set. When this
flag is set, the application needs to explicitly wake up the driver
with a syscall (poll, recvmsg, sendmsg, etc.) to guarantee that Rx
and/or Tx processing will be processed promptly. But the current code
in poll(), sleeps first then wakes up the driver. This means that no
driver processing will occur (baring any interrupts) until the timeout
has expired.

Fix this by checking the need_wakeup flag first and if set, wake the
driver and return to the application. Only if need_wakeup is not set
should the process sleep if there is a timeout set in the poll() call.

Fixes: 77cd0d7b3f ("xsk: add support for need_wakeup flag in AF_XDP rings")
Reported-by: Keith Wiles <keith.wiles@intel.com>
Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Link: https://lore.kernel.org/bpf/20211214102607.7677-1-magnus.karlsson@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Magnus Karlsson 2021-12-14 11:26:07 +01:00 committed by Greg Kroah-Hartman
parent 29e9fdf7b6
commit 095ad3969b
1 changed files with 2 additions and 2 deletions
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4
net/xdp/xsk.c
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@ -434,8 +434,6 @@ static __poll_t xsk_poll(struct file *file, struct socket *sock,
struct xdp_sock *xs = xdp_sk(sk);
struct xdp_umem *umem;
sock_poll_wait(file, sock, wait);
if (unlikely(!xsk_is_bound(xs)))
return mask;
@ -447,6 +445,8 @@ static __poll_t xsk_poll(struct file *file, struct socket *sock,
else
/* Poll needs to drive Tx also in copy mode */
__xsk_sendmsg(sk);
} else {
sock_poll_wait(file, sock, wait);
}
if (xs->rx && !xskq_empty_desc(xs->rx))