Ok, so we can skip below block according to this assumption:
for (i = 0; i < req->tp_block_nr; i++) {
void *ptr = pg_vec[i];
int k;
for (k = 0; k < rb->frames_per_block; k++) {
__packet_set_status(po, ptr, TP_STATUS_KERNEL);
ptr += req->tp_frame_size;
}
Yes, we can also add a check for po->mapped in
I'm not sure to understand:
Let me, sum up :
* when setting or resizing the ring: we have to return an error if:
- someone has mapped the socket (1.a)
- sending is ongoing - tx_pending_skb != 0 (1.b)
- a send() procedure is ongoing (1.c)
* when closing the socket, we have to return an error if:
- sending is ongoing - tx_pending_skb != 0 (2.a)
- a send() procedure is ongoing (2.b)
* during do-while loop of send(),:
- protect ring against simultaneous send() (3.a)
- ensure that ring is not resized (3.b) (linked with 1.c)
Our main issue is when: tx_pending_skb = 0, Thread A starts to send a
packet while Thread B unmaps and resizes the ring.
Thread B can potentially resizes the ring until increment of
tx_pending_skb in Thread A.
- loop can continue even if ring is not mapped (3.c), this has no
sense but it is not critical
* when executing the destructor callback:
- we must ensure that ring structure has not changed since send() (4.a)
(1.a) can be done with po->mmaped check in packet_setsockopt()
(1.b) and (2.a) can be done as you said : tx_pending_skb != 0 check
when sizing buffer in packet_set_ring()
(3.a) by a mutex M outside of the do-while loop
(1.c), (2.b) and (3.b) can be performed thanks to the same mutex M and
mutex_trylock() in packet_set_ring(). An error is returned if we can't
take the mutex . The mutex is released at the end of packet_set_ring()
call.
(4.a) is validated with tx_pending_skb increment, (3.b),(1.b) and (2.a)
Do I miss ...
