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Commit 28ed3ab3 authored by Chris Lew's avatar Chris Lew
Browse files

net: qrtr: Remove rcu logic for port lookup/remove 



synchronize_rcu() is slow and can create delays on creating/removing
sockets.

Some clients have latency requirements for spinning off a
thread that creates a client and lookup sockets for some sessions. They
close the lookup socket during this sequence which causes delays. Each
call to synchronize_rcu takes 20-40 ms which is too long.

Remove the rcu logic and change qrtr_port_lock to a spinlock so it can
be used in qrtr_port_lookup which may be used in atomic context.

Change-Id: I3244e31d3ca0599df794d3936033735bcdd3e972
Signed-off-by: default avatarChris Lew <clew@codeaurora.org>
parent 9f4ad556

net/qrtr/qrtr.c

+12 −12
Original line number Diff line number Diff line
@@ -128,7 +128,7 @@ static DECLARE_RWSEM(qrtr_epts_lock); 


/* local port allocation management */

static DEFINE_IDR(qrtr_ports);

static DEFINE_MUTEX(qrtr_port_lock);

static DEFINE_SPINLOCK(qrtr_port_lock);



/**

 * struct qrtr_node - endpoint node
@@ -1191,15 +1191,16 @@ EXPORT_SYMBOL_GPL(qrtr_endpoint_unregister); 
static struct qrtr_sock *qrtr_port_lookup(int port)

{

	struct qrtr_sock *ipc;

	unsigned long flags;



	if (port == QRTR_PORT_CTRL)

		port = 0;



	rcu_read_lock();

	spin_lock_irqsave(&qrtr_port_lock, flags);

	ipc = idr_find(&qrtr_ports, port);

	if (ipc)

		sock_hold(&ipc->sk);

	rcu_read_unlock();

	spin_unlock_irqrestore(&qrtr_port_lock, flags);



	return ipc;

}
@@ -1261,6 +1262,7 @@ static void qrtr_send_del_client(struct qrtr_sock *ipc) 
static void qrtr_port_remove(struct qrtr_sock *ipc)

{

	int port = ipc->us.sq_port;

	unsigned long flags;



	qrtr_send_del_client(ipc);

	if (port == QRTR_PORT_CTRL)
@@ -1268,13 +1270,9 @@ static void qrtr_port_remove(struct qrtr_sock *ipc) 


	__sock_put(&ipc->sk);



	mutex_lock(&qrtr_port_lock);

	spin_lock_irqsave(&qrtr_port_lock, flags);

	idr_remove(&qrtr_ports, port);

	mutex_unlock(&qrtr_port_lock);



	/* Ensure that if qrtr_port_lookup() did enter the RCU read section we

	 * wait for it to up increment the refcount */

	synchronize_rcu();

	spin_unlock_irqrestore(&qrtr_port_lock, flags);

}



/* Assign port number to socket.
@@ -1348,6 +1346,7 @@ static int __qrtr_bind(struct socket *sock, 
{

	struct qrtr_sock *ipc = qrtr_sk(sock->sk);

	struct sock *sk = sock->sk;

	unsigned long flags;

	int port;

	int rc;
@@ -1355,17 +1354,18 @@ static int __qrtr_bind(struct socket *sock, 
	if (!zapped && addr->sq_port == ipc->us.sq_port)

		return 0;



	mutex_lock(&qrtr_port_lock);

	spin_lock_irqsave(&qrtr_port_lock, flags);

	port = addr->sq_port;

	rc = qrtr_port_assign(ipc, &port);

	if (rc) {

		mutex_unlock(&qrtr_port_lock);

		spin_unlock_irqrestore(&qrtr_port_lock, flags);

		return rc;

	}

	/* Notify all open ports about the new controller */

	if (port == QRTR_PORT_CTRL)

		qrtr_reset_ports();

	mutex_unlock(&qrtr_port_lock);

	spin_unlock_irqrestore(&qrtr_port_lock, flags);





	if (port == QRTR_PORT_CTRL) {

		struct qrtr_node *node;