Re: [PATCH net-next v2 1/6] net/tls: Bound consecutive no-data records in tls_sw_read_sock()

[Jakub Kicinski <kuba@kernel.org>]

On Mon, 20 Jul 2026 10:27:55 -0400 Chuck Lever wrote:
> A record that delivers no payload -- an empty TLS 1.3 data record
> today, a control record once read_sock_rectype() lands -- leaves
> tls_sw_read_sock() in its loop without advancing the caller's read
> descriptor. A peer that streams such records keeps the receive loop
> running, and the socket lock held, for as long as the records
> arrive.
> 
> Cap the number of consecutive no-data records consumed per call. The
> count resets on any record that delivers bytes, so a normal stream
> is unaffected; a peer supplying only empty records is bounded to
> TLS_RX_NODATA_LIMIT iterations before the call returns 0. read_sock
> consumers treat that as "no progress, re-poll" rather than EOF, so
> the connection stays up and makes progress once real data arrives.
> 
> Only tls_sw_read_sock() needs this cap. Its consumers drive the receive
> loop from kernel context -- a work item or service thread holding the
> socket lock across the whole call with no return to userspace -- so an
> unbounded empty-record stream keeps that context and the lock pinned
> for as long as the flood lasts. The cap supplies the return boundary
> that a system call would otherwise provide. tls_sw_splice_read()
> and tls_sw_recvmsg() already have one: they run in the calling task's
> context, reschedule while draining the socket backlog (cond_resched()
> in __release_sock()), and drop the socket lock when the call returns. A
> flood there costs the caller only its own scheduler time, so the cap
> would add nothing.

Is this alluding to PREEMPT_NONE (which for practical purposes is 
no longer a thing AFAIU)?