netdev - [PATCH net-next v2 3/6] tipc: avoid to unnecessary process switch under non-block mode

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Date:	Wed, 5 Mar 2014 08:56:15 +0100
From:	<erik.hugne@...csson.com>
To:	<netdev@...r.kernel.org>, <tipc-discussion@...ts.sourceforge.net>,
	<jon.maloy@...csson.com>, <maloy@...jonn.com>
CC:	<ying.xue@...driver.com>, <paul.gortmaker@...driver.com>,
	<richard.alpe@...csson.com>
Subject: [PATCH net-next v2 3/6] tipc: avoid to unnecessary process switch under non-block mode

From: Ying Xue <ying.xue@...driver.com>

When messages are received via tipc socket under non-block mode,
schedule_timeout() is called in tipc_wait_for_rcvmsg(), that is,
the process of receiving messages will be scheduled once although
timeout value passed to schedule_timeout() is 0. The same issue
exists in accept()/wait_for_accept(). To avoid this unnecessary
process switch, we only call schedule_timeout() if the timeout
value is non-zero.

Signed-off-by: Ying Xue <ying.xue@...driver.com>
Reviewed-by: Erik Hugne <erik.hugne@...csson.com>
Reviewed-by: Jon Maloy <jon.maloy@...csson.com>
---
 net/tipc/socket.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index fb88597..96978fb 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1001,7 +1001,7 @@ static int tipc_wait_for_rcvmsg(struct socket *sock, long timeo)
 
 	for (;;) {
 		prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
-		if (skb_queue_empty(&sk->sk_receive_queue)) {
+		if (timeo && skb_queue_empty(&sk->sk_receive_queue)) {
 			if (sock->state == SS_DISCONNECTING) {
 				err = -ENOTCONN;
 				break;
@@ -1627,7 +1627,7 @@ static int tipc_wait_for_accept(struct socket *sock, long timeo)
 	for (;;) {
 		prepare_to_wait_exclusive(sk_sleep(sk), &wait,
 					  TASK_INTERRUPTIBLE);
-		if (skb_queue_empty(&sk->sk_receive_queue)) {
+		if (timeo && skb_queue_empty(&sk->sk_receive_queue)) {
 			release_sock(sk);
 			timeo = schedule_timeout(timeo);
 			lock_sock(sk);
-- 
1.8.3.2

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