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

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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: David 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: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
David Howells 2024-12-04 07:46:45 +00:00 committed by Jakub Kicinski
parent 976b0ca5aa
commit 6396b48ac0
2 changed files with 7 additions and 5 deletions
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8
net/rxrpc/sendmsg.c
View File

@ -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);

4
net/rxrpc/txbuf.c
View File

@ -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);