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rxrpc: Move call state changes from sendmsg to I/O thread
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Move all the call state changes that are made in rxrpc_sendmsg() to the I/O
thread.  This is a step towards removing the call state lock.

This requires the switch to the RXRPC_CALL_CLIENT_AWAIT_REPLY and
RXRPC_CALL_SERVER_SEND_REPLY states to be done when the last packet is
decanted from ->tx_sendmsg to ->tx_buffer in the I/O thread, not when it is
added to ->tx_sendmsg by sendmsg().

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Marc Dionne <marc.dionne@auristor.com>
cc: linux-afs@lists.infradead.org
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David Howells committed Jan 6, 2023
1 parent d41b3f5 commit 2d68942
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Showing 3 changed files with 63 additions and 60 deletions.
4 changes: 2 additions & 2 deletions Documentation/networking/rxrpc.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -880,8 +880,8 @@ The kernel interface functions are as follows:

notify_end_rx can be NULL or it can be used to specify a function to be
called when the call changes state to end the Tx phase. This function is
called with the call-state spinlock held to prevent any reply or final ACK
from being delivered first.
called with a spinlock held to prevent the last DATA packet from being
transmitted until the function returns.

(#) Receive data from a call::

Expand Down
50 changes: 48 additions & 2 deletions net/rxrpc/call_event.c
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Original file line number Diff line number Diff line change
Expand Up @@ -251,6 +251,50 @@ void rxrpc_resend(struct rxrpc_call *call, struct sk_buff *ack_skb)
_leave("");
}

/*
* Start transmitting the reply to a service. This cancels the need to ACK the
* request if we haven't yet done so.
*/
static void rxrpc_begin_service_reply(struct rxrpc_call *call)
{
unsigned long now;

write_lock(&call->state_lock);

if (call->state == RXRPC_CALL_SERVER_ACK_REQUEST) {
now = jiffies;
call->state = RXRPC_CALL_SERVER_SEND_REPLY;
WRITE_ONCE(call->delay_ack_at, now + MAX_JIFFY_OFFSET);
if (call->ackr_reason == RXRPC_ACK_DELAY)
call->ackr_reason = 0;
trace_rxrpc_timer(call, rxrpc_timer_init_for_send_reply, now);
}

write_unlock(&call->state_lock);
}

/*
* Close the transmission phase. After this point there is no more data to be
* transmitted in the call.
*/
static void rxrpc_close_tx_phase(struct rxrpc_call *call)
{
_debug("________awaiting reply/ACK__________");

write_lock(&call->state_lock);
switch (call->state) {
case RXRPC_CALL_CLIENT_SEND_REQUEST:
call->state = RXRPC_CALL_CLIENT_AWAIT_REPLY;
break;
case RXRPC_CALL_SERVER_SEND_REPLY:
call->state = RXRPC_CALL_SERVER_AWAIT_ACK;
break;
default:
break;
}
write_unlock(&call->state_lock);
}

static bool rxrpc_tx_window_has_space(struct rxrpc_call *call)
{
unsigned int winsize = min_t(unsigned int, call->tx_winsize,
Expand Down Expand Up @@ -285,6 +329,9 @@ static void rxrpc_decant_prepared_tx(struct rxrpc_call *call)
call->tx_top = txb->seq;
list_add_tail(&txb->call_link, &call->tx_buffer);

if (txb->wire.flags & RXRPC_LAST_PACKET)
rxrpc_close_tx_phase(call);

rxrpc_transmit_one(call, txb);

if (!rxrpc_tx_window_has_space(call))
Expand All @@ -298,12 +345,11 @@ static void rxrpc_transmit_some_data(struct rxrpc_call *call)
case RXRPC_CALL_SERVER_ACK_REQUEST:
if (list_empty(&call->tx_sendmsg))
return;
rxrpc_begin_service_reply(call);
fallthrough;

case RXRPC_CALL_SERVER_SEND_REPLY:
case RXRPC_CALL_SERVER_AWAIT_ACK:
case RXRPC_CALL_CLIENT_SEND_REQUEST:
case RXRPC_CALL_CLIENT_AWAIT_REPLY:
if (!rxrpc_tx_window_has_space(call))
return;
if (list_empty(&call->tx_sendmsg)) {
Expand Down
69 changes: 13 additions & 56 deletions net/rxrpc/sendmsg.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -189,7 +189,6 @@ static void rxrpc_queue_packet(struct rxrpc_sock *rx, struct rxrpc_call *call,
struct rxrpc_txbuf *txb,
rxrpc_notify_end_tx_t notify_end_tx)
{
unsigned long now;
rxrpc_seq_t seq = txb->seq;
bool last = test_bit(RXRPC_TXBUF_LAST, &txb->flags), poke;

Expand All @@ -212,36 +211,10 @@ static void rxrpc_queue_packet(struct rxrpc_sock *rx, struct rxrpc_call *call,
poke = list_empty(&call->tx_sendmsg);
list_add_tail(&txb->call_link, &call->tx_sendmsg);
call->tx_prepared = seq;
if (last)
rxrpc_notify_end_tx(rx, call, notify_end_tx);
spin_unlock(&call->tx_lock);

if (last || call->state == RXRPC_CALL_SERVER_ACK_REQUEST) {
_debug("________awaiting reply/ACK__________");
write_lock(&call->state_lock);
switch (call->state) {
case RXRPC_CALL_CLIENT_SEND_REQUEST:
call->state = RXRPC_CALL_CLIENT_AWAIT_REPLY;
rxrpc_notify_end_tx(rx, call, notify_end_tx);
break;
case RXRPC_CALL_SERVER_ACK_REQUEST:
call->state = RXRPC_CALL_SERVER_SEND_REPLY;
now = jiffies;
WRITE_ONCE(call->delay_ack_at, now + MAX_JIFFY_OFFSET);
if (call->ackr_reason == RXRPC_ACK_DELAY)
call->ackr_reason = 0;
trace_rxrpc_timer(call, rxrpc_timer_init_for_send_reply, now);
if (!last)
break;
fallthrough;
case RXRPC_CALL_SERVER_SEND_REPLY:
call->state = RXRPC_CALL_SERVER_AWAIT_ACK;
rxrpc_notify_end_tx(rx, call, notify_end_tx);
break;
default:
break;
}
write_unlock(&call->state_lock);
}

if (poke)
rxrpc_poke_call(call, rxrpc_call_poke_start);
}
Expand Down Expand Up @@ -280,8 +253,13 @@ static int rxrpc_send_data(struct rxrpc_sock *rx,
ret = -EPROTO;
if (state != RXRPC_CALL_CLIENT_SEND_REQUEST &&
state != RXRPC_CALL_SERVER_ACK_REQUEST &&
state != RXRPC_CALL_SERVER_SEND_REPLY)
state != RXRPC_CALL_SERVER_SEND_REPLY) {
/* Request phase complete for this client call */
trace_rxrpc_abort(call->debug_id, rxrpc_sendmsg_late_send,
call->cid, call->call_id, call->rx_consumed,
0, -EPROTO);
goto maybe_error;
}

ret = -EMSGSIZE;
if (call->tx_total_len != -1) {
Expand Down Expand Up @@ -573,7 +551,6 @@ rxrpc_new_client_call_for_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg,
int rxrpc_do_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg, size_t len)
__releases(&rx->sk.sk_lock.slock)
{
enum rxrpc_call_state state;
struct rxrpc_call *call;
unsigned long now, j;
bool dropped_lock = false;
Expand Down Expand Up @@ -672,11 +649,7 @@ int rxrpc_do_sendmsg(struct rxrpc_sock *rx, struct msghdr *msg, size_t len)
break;
}

state = rxrpc_call_state(call);
_debug("CALL %d USR %lx ST %d on CONN %p",
call->debug_id, call->user_call_ID, state, call->conn);

if (state >= RXRPC_CALL_COMPLETE) {
if (rxrpc_call_is_complete(call)) {
/* it's too late for this call */
ret = -ESHUTDOWN;
} else if (p.command == RXRPC_CMD_SEND_ABORT) {
Expand Down Expand Up @@ -722,7 +695,7 @@ int rxrpc_kernel_send_data(struct socket *sock, struct rxrpc_call *call,
bool dropped_lock = false;
int ret;

_enter("{%d,%s},", call->debug_id, rxrpc_call_states[call->state]);
_enter("{%d},", call->debug_id);

ASSERTCMP(msg->msg_name, ==, NULL);
ASSERTCMP(msg->msg_control, ==, NULL);
Expand All @@ -732,26 +705,10 @@ int rxrpc_kernel_send_data(struct socket *sock, struct rxrpc_call *call,
_debug("CALL %d USR %lx ST %d on CONN %p",
call->debug_id, call->user_call_ID, call->state, call->conn);

switch (rxrpc_call_state(call)) {
case RXRPC_CALL_CLIENT_SEND_REQUEST:
case RXRPC_CALL_SERVER_ACK_REQUEST:
case RXRPC_CALL_SERVER_SEND_REPLY:
ret = rxrpc_send_data(rxrpc_sk(sock->sk), call, msg, len,
notify_end_tx, &dropped_lock);
break;
case RXRPC_CALL_COMPLETE:
read_lock(&call->state_lock);
ret = rxrpc_send_data(rxrpc_sk(sock->sk), call, msg, len,
notify_end_tx, &dropped_lock);
if (ret == -ESHUTDOWN)
ret = call->error;
read_unlock(&call->state_lock);
break;
default:
/* Request phase complete for this client call */
trace_rxrpc_abort(call->debug_id, rxrpc_sendmsg_late_send,
call->cid, call->call_id, call->rx_consumed,
0, -EPROTO);
ret = -EPROTO;
break;
}

if (!dropped_lock)
mutex_unlock(&call->user_mutex);
Expand Down

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