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net: qrtr: Change node mutex to a rw_semaphore

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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: Chris Lew <quic_clew@quicinc.com>
This commit is contained in:
Chris Lew 2022-10-03 09:57:33 -07:00
parent cc60f7fdd8
commit 20cca07151
1 changed files with 34 additions and 7 deletions
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41
net/qrtr/af_qrtr.c
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@ -10,6 +10,7 @@
#include <linux/termios.h> /* For TIOCINQ/OUTQ */
#include <linux/spinlock.h>
#include <linux/wait.h>
#include <linux/rwsem.h>
#include <net/sock.h>
@ -112,7 +113,7 @@ 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_XARRAY_ALLOC(qrtr_ports);
@ -167,6 +168,32 @@ 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
@ -191,7 +218,7 @@ 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);
skb_queue_purge(&node->rx_queue);
@ -217,7 +244,7 @@ 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);
}
/**
@ -612,9 +639,9 @@ 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;
@ -921,7 +948,7 @@ 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;
@ -931,7 +958,7 @@ 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(NULL, skb, type, from, to);