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samples/bpf: Fix possible deadlock in xdpsock 

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
This commit is contained in:
Magnus Karlsson 2020-09-10 10:31:05 +02:00 committed by Alexei Starovoitov
parent 3131cf66d3
commit 5a2a0dd88f
1 changed files with 1 additions and 0 deletions
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samples/bpf/xdpsock_user.c
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@ -1125,6 +1125,7 @@ static void l2fwd(struct xsk_socket_info *xsk, struct pollfd *fds)
while (ret != rcvd) { while (ret != rcvd) {
if (ret < 0) if (ret < 0)
exit_with_error(-ret); exit_with_error(-ret);
complete_tx_l2fwd(xsk, fds);
if (xsk_ring_prod__needs_wakeup(&xsk->tx)) if (xsk_ring_prod__needs_wakeup(&xsk->tx))
kick_tx(xsk); kick_tx(xsk);
ret = xsk_ring_prod__reserve(&xsk->tx, rcvd, &idx_tx); ret = xsk_ring_prod__reserve(&xsk->tx, rcvd, &idx_tx);