tcp_splice: Don't wake up on input data if we can't write it anywhere

If we set the OUT_WAIT_* flag (waiting on EPOLLOUT) for a side of a
given flow, it means that we're blocked, waiting for the receiver to
actually receive data, with a full pipe.

In that case, if we keep EPOLLIN set for the socket on the other side
(our receiving side), we'll get into a loop such as:

  41.0230:          pasta: epoll event on connected spliced TCP socket 108 (events: 0x00000001)
  41.0230:          Flow 1 (TCP connection (spliced)): -1 from read-side call
  41.0230:          Flow 1 (TCP connection (spliced)): -1 from write-side call (passed 8192)
  41.0230:          Flow 1 (TCP connection (spliced)): event at tcp_splice_sock_handler:577
  41.0230:          pasta: epoll event on connected spliced TCP socket 108 (events: 0x00000001)
  41.0230:          Flow 1 (TCP connection (spliced)): -1 from read-side call
  41.0230:          Flow 1 (TCP connection (spliced)): -1 from write-side call (passed 8192)
  41.0230:          Flow 1 (TCP connection (spliced)): event at tcp_splice_sock_handler:577

leading to 100% CPU usage, of course.

Drop EPOLLIN on our receiving side as long when we're waiting for
output readiness on the other side.

Link: https://github.com/containers/podman/issues/23686#issuecomment-2661036584
Link: https://www.reddit.com/r/podman/comments/1iph50j/pasta_high_cpu_on_podman_rootless_container/
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

0 files changed, 0 insertions, 0 deletions