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

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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: Chris Lew <clew@codeaurora.org>
This commit is contained in:
Chris Lew 2020-05-19 18:54:43 -07:00
commit 28ed3ab34f
1 changed files with 12 additions and 12 deletions
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24
net/qrtr/qrtr.c
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@ -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 @@ exit:
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;