Commit 6396b48a authored by David Howells's avatar David Howells Committed by Jakub Kicinski
Browse files

rxrpc: Don't need barrier for ->tx_bottom and ->acks_hard_ack 



We don't need a barrier for the ->tx_bottom value (which indicates the
lowest sequence still in the transmission queue) and the ->acks_hard_ack
value (which tracks the DATA packets hard-ack'd by the latest ACK packet
received and thus indicates which DATA packets can now be discarded) as the
app thread doesn't use either value as a reference to memory to access.
Rather, the app thread merely uses these as a guide to how much space is
available in the transmission queue

Change the code to use READ/WRITE_ONCE() instead.

Also, change rxrpc_check_tx_space() to use the same value for tx_bottom
throughout.

Signed-off-by: default avatarDavid Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
Link: https://patch.msgid.link/20241204074710.990092-18-dhowells@redhat.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 976b0ca5

net/rxrpc/sendmsg.c

+5 −3
Original line number Diff line number Diff line
@@ -94,9 +94,11 @@ static int rxrpc_wait_to_be_connected(struct rxrpc_call *call, long *timeo) 
 */

static bool rxrpc_check_tx_space(struct rxrpc_call *call, rxrpc_seq_t *_tx_win)

{

	rxrpc_seq_t tx_bottom = READ_ONCE(call->tx_bottom);



	if (_tx_win)

		*_tx_win = call->tx_bottom;

	return call->tx_prepared - call->tx_bottom < 256;

		*_tx_win = tx_bottom;

	return call->tx_prepared - tx_bottom < 256;

}



/*
@@ -138,7 +140,7 @@ static int rxrpc_wait_for_tx_window_waitall(struct rxrpc_sock *rx, 
		rtt = 2;



	timeout = rtt;

	tx_start = smp_load_acquire(&call->acks_hard_ack);

	tx_start = READ_ONCE(call->acks_hard_ack);



	for (;;) {

		set_current_state(TASK_UNINTERRUPTIBLE);

net/rxrpc/txbuf.c

+2 −2
Original line number Diff line number Diff line
@@ -214,14 +214,14 @@ void rxrpc_shrink_call_tx_buffer(struct rxrpc_call *call) 


	while ((txb = list_first_entry_or_null(&call->tx_buffer,

					       struct rxrpc_txbuf, call_link))) {

		hard_ack = smp_load_acquire(&call->acks_hard_ack);

		hard_ack = call->acks_hard_ack;

		if (before(hard_ack, txb->seq))

			break;



		if (txb->seq != call->tx_bottom + 1)

			rxrpc_see_txbuf(txb, rxrpc_txbuf_see_out_of_step);

		ASSERTCMP(txb->seq, ==, call->tx_bottom + 1);

		smp_store_release(&call->tx_bottom, call->tx_bottom + 1);

		WRITE_ONCE(call->tx_bottom, call->tx_bottom + 1);

		list_del_rcu(&txb->call_link);



		trace_rxrpc_txqueue(call, rxrpc_txqueue_dequeue);