srvinbox.h File Reference

SPSC ring for worker-to-worker broadcast handoff. More...

#include "common/platform/sys/syscall.h"

Go to the source code of this file.

Data Structures
struct	wired_srvinbox_slot
	One ring slot: a datagram payload and its length. More...
struct	wired_srvinbox_ring
	A single-producer/single-consumer ring of depth WIRED_SRVINBOX_DEPTH. More...

Macros
#define	WIRED_SRVINBOX_DEPTH   4u
	Ring capacity; must stay a power of two (WIRED_SRVINBOX_DEPTH - 1 is used as the index mask).
#define	WIRED_SRVINBOX_SLOT_MAX   1200u
	Max payload bytes one slot holds – sized for one QUIC datagram (srvrun's own dg_pending_buf is 1200 bytes; this matches).

Functions
void	wired_srvinbox_ring_init (wired_srvinbox_ring *r)
	Zero-initialize r (prod = cons = 0, empty ring).
int	wired_srvinbox_push (wired_srvinbox_ring *r, const u8 *data, usz len)
	Push one message (producer side only).
usz	wired_srvinbox_pop (wired_srvinbox_ring *r, u8 *out_buf, usz out_cap)
	Pop one message (consumer side only) into out_buf.

Detailed Description

SPSC ring for worker-to-worker broadcast handoff.

One ring carries best-effort datagram-sized messages from exactly one producer worker to exactly one consumer worker; an N-worker mesh is N*N of these (srvrun.c's broadcast registry owns the mesh, this file only owns one ring's push/pop contract).

Same free-running-counter + ACQUIRE/RELEASE + look-then-reload idiom as transport/io/xdp/xskring/xskring.c, specialized to a fixed-size datagram slot instead of a generic descriptor array: push/pop do their own check+write+publish / check+read+release in one call each, since a datagram producer/consumer never needs to split reservation from publication the way the AF_XDP rings do. Unlike xskring's xskring side struct, there is no per-side cached_prod/cached_cons field – push/ pop are stateless across calls, so every full/empty look re-reads the shared prod/cons cell (still just one extra ACQUIRE load in the common case, since the "reload" only ever runs when the first look already showed full/empty).

Function Documentation

wired_srvinbox_pop()

usz wired_srvinbox_pop	(	wired_srvinbox_ring *	r,
		u8 *	out_buf,
		usz	out_cap )

Pop one message (consumer side only) into out_buf.

If the ring looks empty, prod is re-read with ACQUIRE and re-checked once before reporting empty – mirrors xskring_cons_peek's look-then-recheck idiom. out_cap must be >= the popped message's length or nothing is popped (the slot stays queued, so a caller that always passes a WIRED_SRVINBOX_SLOT_MAX buffer never hits this): this SDK's callers all forward straight into a srvrun_queue_datagram-sized buffer, so undersizing is not expected to happen in practice.

Parameters

r	ring to pop from
out_buf	destination for the payload bytes
out_cap	capacity of out_buf

Returns

number of bytes popped (== the message's length), 0 if the ring was empty or out_buf was too small to hold the next message

wired_srvinbox_push()

int wired_srvinbox_push	(	wired_srvinbox_ring *	r,
		const u8 *	data,
		usz	len )

Push one message (producer side only).

If the ring looks full, cons is re-read with ACQUIRE and the fullness re-checked once before dropping – the same look-then-recheck idiom as xskring_prod_reserve, folded into one call since a datagram producer never needs a separate reserve/submit split.

Parameters

r	ring to push into
data	payload bytes, copied into the slot
len	payload length; > WIRED_SRVINBOX_SLOT_MAX is rejected (0 returned, nothing sent)

Returns

1 if the message was published, 0 if dropped (ring full after the reload, or len too large)