cnic: Fix locking in init/exit calls.

The slow path ulp_init and ulp_exit calls to the bnx2i driver
are sleepable calls and therefore should not be protected using
rcu_read_lock.  Fix it by using mutex and refcount during these
calls.  cnic_unregister_driver() will now wait for the refcount
to go to zero before completing the call.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Reviewed-by: Benjamin Li <benli@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 40 insertions, 9 deletions

diff --git a/drivers/net/cnic.c b/drivers/net/cnic.c
index 4ff618a7afd..74c342959b7 100644
--- a/drivers/net/cnic.c
+++ b/drivers/net/cnic.c
@@ -138,6 +138,16 @@ static struct cnic_dev *cnic_from_netdev(struct net_device *netdev)
         return NULL;
 }
 
+static inline void ulp_get(struct cnic_ulp_ops *ulp_ops)
+{
+        atomic_inc(&ulp_ops->ref_count);
+}
+
+static inline void ulp_put(struct cnic_ulp_ops *ulp_ops)
+{
+        atomic_dec(&ulp_ops->ref_count);
+}
+
 static void cnic_ctx_wr(struct cnic_dev *dev, u32 cid_addr, u32 off, u32 val)
 {
         struct cnic_local *cp = dev->cnic_priv;
@@ -358,6 +368,7 @@ int cnic_register_driver(int ulp_type, struct cnic_ulp_ops *ulp_ops)
         }
         read_unlock(&cnic_dev_lock);
 
+        atomic_set(&ulp_ops->ref_count, 0);
         rcu_assign_pointer(cnic_ulp_tbl[ulp_type], ulp_ops);
         mutex_unlock(&cnic_lock);
 
@@ -379,6 +390,8 @@ int cnic_register_driver(int ulp_type, struct cnic_ulp_ops *ulp_ops)
 int cnic_unregister_driver(int ulp_type)
 {
         struct cnic_dev *dev;
+        struct cnic_ulp_ops *ulp_ops;
+        int i = 0;
 
         if (ulp_type >= MAX_CNIC_ULP_TYPE) {
                 printk(KERN_ERR PFX "cnic_unregister_driver: Bad type %d\n",
@@ -386,7 +399,8 @@ int cnic_unregister_driver(int ulp_type)
                 return -EINVAL;
         }
         mutex_lock(&cnic_lock);
-        if (!cnic_ulp_tbl[ulp_type]) {
+        ulp_ops = cnic_ulp_tbl[ulp_type];
+        if (!ulp_ops) {
                 printk(KERN_ERR PFX "cnic_unregister_driver: Type %d has not "
                                     "been registered\n", ulp_type);
                 goto out_unlock;
@@ -411,6 +425,14 @@ int cnic_unregister_driver(int ulp_type)
 
         mutex_unlock(&cnic_lock);
         synchronize_rcu();
+        while ((atomic_read(&ulp_ops->ref_count) != 0) && (i < 20)) {
+                msleep(100);
+                i++;
+        }
+
+        if (atomic_read(&ulp_ops->ref_count) != 0)
+                printk(KERN_WARNING PFX "%s: Failed waiting for ref count to go"
+                                        " to zero.\n", dev->netdev->name);
         return 0;
 
 out_unlock:
@@ -1161,19 +1183,23 @@ static void cnic_ulp_init(struct cnic_dev *dev)
         int i;
         struct cnic_local *cp = dev->cnic_priv;
 
-        rcu_read_lock();
         for (i = 0; i < MAX_CNIC_ULP_TYPE_EXT; i++) {
                 struct cnic_ulp_ops *ulp_ops;
 
-                ulp_ops = rcu_dereference(cnic_ulp_tbl[i]);
-                if (!ulp_ops || !ulp_ops->cnic_init)
+                mutex_lock(&cnic_lock);
+                ulp_ops = cnic_ulp_tbl[i];
+                if (!ulp_ops || !ulp_ops->cnic_init) {
+                        mutex_unlock(&cnic_lock);
                         continue;
+                }
+                ulp_get(ulp_ops);
+                mutex_unlock(&cnic_lock);
 
                 if (!test_and_set_bit(ULP_F_INIT, &cp->ulp_flags[i]))
                         ulp_ops->cnic_init(dev);
 
+                ulp_put(ulp_ops);
         }
-        rcu_read_unlock();
 }
 
 static void cnic_ulp_exit(struct cnic_dev *dev)
@@ -1181,19 +1207,23 @@ static void cnic_ulp_exit(struct cnic_dev *dev)
         int i;
         struct cnic_local *cp = dev->cnic_priv;
 
-        rcu_read_lock();
         for (i = 0; i < MAX_CNIC_ULP_TYPE_EXT; i++) {
                 struct cnic_ulp_ops *ulp_ops;
 
-                ulp_ops = rcu_dereference(cnic_ulp_tbl[i]);
-                if (!ulp_ops || !ulp_ops->cnic_exit)
+                mutex_lock(&cnic_lock);
+                ulp_ops = cnic_ulp_tbl[i];
+                if (!ulp_ops || !ulp_ops->cnic_exit) {
+                        mutex_unlock(&cnic_lock);
                         continue;
+                }
+                ulp_get(ulp_ops);
+                mutex_unlock(&cnic_lock);
 
                 if (test_and_clear_bit(ULP_F_INIT, &cp->ulp_flags[i]))
                         ulp_ops->cnic_exit(dev);
 
+                ulp_put(ulp_ops);
         }
-        rcu_read_unlock();
 }
 
 static int cnic_cm_offload_pg(struct cnic_sock *csk)
diff --git a/drivers/net/cnic_if.h b/drivers/net/cnic_if.h
index d1bce27ee99..a49235739ee 100644
--- a/drivers/net/cnic_if.h
+++ b/drivers/net/cnic_if.h
@@ -290,6 +290,7 @@ struct cnic_ulp_ops {
         void (*iscsi_nl_send_msg)(struct cnic_dev *dev, u32 msg_type,
                                   char *data, u16 data_size);
         struct module *owner;
+        atomic_t ref_count;
 };
 
 extern int cnic_register_driver(int ulp_type, struct cnic_ulp_ops *ulp_ops);