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    Subject[PATCH 5.4 66/71] Revert "xsk: Do not sleep in poll() when need_wakeup set"
    Date
    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
    @@ -434,6 +434,8 @@ static __poll_t xsk_poll(struct file *fi
    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;

    @@ -445,8 +447,6 @@ 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_empty_desc(xs->rx))

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