Re: [PATCH net v2] net/smc: don't spin in smc_rx_recvmsg() while a pipe holds spliced data

[Paolo Abeni]

On 10/29/26 09:03, Bryam Vargas wrote:
> While bytes spliced off the RMB are still in a pipe, recvmsg() waits
> for the pipe to release them before it copies the data behind them.
> The path to that wait skips the timeout and signal checks, and
> smc_rx_wait() returns at once on RCV_SHUTDOWN. With a signal pending,
> after SHUT_RD, or once the peer closes or shuts down writing,
> recvmsg() spins on a CPU until the pipe is drained, and SIGKILL cannot
> stop it. MSG_DONTWAIT and an expired SO_RCVTIMEO wait there too
> instead of returning -EAGAIN.
>
> Check the timeout and signals before that wait, and end it when the
> pipe releases the data or the connection is killed, not on RCV_SHUTDOWN.
> A zero-length read returns 0 without waiting for the pipe; a
> non-blocking one returns -EAGAIN while poll() still reports the socket
> readable (splice() can still take those bytes).

@SMC experts, please review. IMHO the above trade-off sounds like a better
solution is needed.

/P