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Commit 5e6fd7cd authored by Chris Lew's avatar Chris Lew
Browse files

net: qrtr: Change node mutex to a rw_semaphore 



There is a chance for a remote processor to become unresponsive while
QRTR is trying to broadcast a control message. This results in the node
lock being held for an extended period of time and prevents node lookup
which is needed to send messages.

Change the mutex to a rw_semaphore to allow concurrency during node
lookups and broadcasts.

Change-Id: I2e3fdde22edaac64f164cf08900e9d09b16c380d
Signed-off-by: default avatarChris Lew <clew@codeaurora.org>
parent 01b08fdd

net/qrtr/qrtr.c

+34 −7
Original line number Diff line number Diff line
@@ -10,6 +10,7 @@ 
#include <linux/numa.h>

#include <linux/spinlock.h>

#include <linux/wait.h>

#include <linux/rwsem.h>



#include <net/sock.h>
@@ -110,7 +111,7 @@ static DEFINE_SPINLOCK(qrtr_nodes_lock); 
/* broadcast list */

static LIST_HEAD(qrtr_all_nodes);

/* lock for qrtr_all_nodes and node reference */

static DEFINE_MUTEX(qrtr_node_lock);

static DECLARE_RWSEM(qrtr_node_lock);



/* local port allocation management */

static DEFINE_IDR(qrtr_ports);
@@ -168,6 +169,32 @@ static int qrtr_bcast_enqueue(struct qrtr_node *node, struct sk_buff *skb, 
static struct qrtr_sock *qrtr_port_lookup(int port);

static void qrtr_port_put(struct qrtr_sock *ipc);



static bool refcount_dec_and_rwsem_lock(refcount_t *r,

					struct rw_semaphore *sem)

{

	if (refcount_dec_not_one(r))

		return false;



	down_write(sem);

	if (!refcount_dec_and_test(r)) {

		up_write(sem);

		return false;

	}



	return true;

}



static inline int kref_put_rwsem_lock(struct kref *kref,

				      void (*release)(struct kref *kref),

				      struct rw_semaphore *sem)

{

	if (refcount_dec_and_rwsem_lock(&kref->refcount, sem)) {

		release(kref);

		return 1;

	}

	return 0;

}



/* Release node resources and free the node.

 *

 * Do not call directly, use qrtr_node_release.  To be used with
@@ -186,7 +213,7 @@ static void __qrtr_node_release(struct kref *kref) 
	spin_unlock_irqrestore(&qrtr_nodes_lock, flags);



	list_del(&node->item);

	mutex_unlock(&qrtr_node_lock);

	up_write(&qrtr_node_lock);



	/* Free tx flow counters */

	radix_tree_for_each_slot(slot, &node->qrtr_tx_flow, &iter, 0) {
@@ -211,7 +238,7 @@ static void qrtr_node_release(struct qrtr_node *node) 
{

	if (!node)

		return;

	kref_put_mutex(&node->ref, __qrtr_node_release, &qrtr_node_lock);

	kref_put_rwsem_lock(&node->ref, __qrtr_node_release, &qrtr_node_lock);

}



/**
@@ -583,9 +610,9 @@ int qrtr_endpoint_register(struct qrtr_endpoint *ep, unsigned int nid) 


	qrtr_node_assign(node, nid);



	mutex_lock(&qrtr_node_lock);

	down_write(&qrtr_node_lock);

	list_add(&node->item, &qrtr_all_nodes);

	mutex_unlock(&qrtr_node_lock);

	up_write(&qrtr_node_lock);

	ep->node = node;



	return 0;
@@ -886,7 +913,7 @@ static int qrtr_bcast_enqueue(struct qrtr_node *node, struct sk_buff *skb, 
{

	struct sk_buff *skbn;



	mutex_lock(&qrtr_node_lock);

	down_read(&qrtr_node_lock);

	list_for_each_entry(node, &qrtr_all_nodes, item) {

		if (node->nid == QRTR_EP_NID_AUTO)

			continue;
@@ -896,7 +923,7 @@ static int qrtr_bcast_enqueue(struct qrtr_node *node, struct sk_buff *skb, 
		skb_set_owner_w(skbn, skb->sk);

		qrtr_node_enqueue(node, skbn, type, from, to);

	}

	mutex_unlock(&qrtr_node_lock);

	up_read(&qrtr_node_lock);



	qrtr_local_enqueue(node, skb, type, from, to);