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    Subject[PATCH AUTOSEL 5.4 35/80] samples/bpf: Fix possible deadlock in xdpsock
    Date
    From: Magnus Karlsson <magnus.karlsson@intel.com>

    [ Upstream commit 5a2a0dd88f0f267ac5953acd81050ae43a82201f ]

    Fix a possible deadlock in the l2fwd application in xdpsock that can
    occur when there is no space in the Tx ring. There are two ways to get
    the kernel to consume entries in the Tx ring: calling sendto() to make
    it send packets and freeing entries from the completion ring, as the
    kernel will not send a packet if there is no space for it to add a
    completion entry in the completion ring. The Tx loop in l2fwd only
    used to call sendto(). This patches adds cleaning the completion ring
    in that loop.

    Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>
    Link: https://lore.kernel.org/bpf/1599726666-8431-3-git-send-email-magnus.karlsson@gmail.com
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    samples/bpf/xdpsock_user.c | 1 +
    1 file changed, 1 insertion(+)

    diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
    index df011ac334022..79d1005ff2ee3 100644
    --- a/samples/bpf/xdpsock_user.c
    +++ b/samples/bpf/xdpsock_user.c
    @@ -677,6 +677,7 @@ static void l2fwd(struct xsk_socket_info *xsk, struct pollfd *fds)
    while (ret != rcvd) {
    if (ret < 0)
    exit_with_error(-ret);
    + complete_tx_l2fwd(xsk, fds);
    if (xsk_ring_prod__needs_wakeup(&xsk->tx))
    kick_tx(xsk);
    ret = xsk_ring_prod__reserve(&xsk->tx, rcvd, &idx_tx);
    --
    2.25.1
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