cxgb4: Fix race condition in cleanup

There is a possible race condition when we unregister the PCI Driver and then
flush/destroy the global "workq". This could lead to situations where there
are tasks on the Work Queue with references to now deleted adapter data
structures. Instead, have per-adapter Work Queues which were instantiated and
torn down in init_one() and remove_one(), respectively.

v2: Remove unnecessary call to flush_workqueue() before destroy_workqueue()

Signed-off-by: Anish Bhatt <anish@chelsio.com>
Signed-off-by: Casey Leedom <leedom@chelsio.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 19 insertions, 14 deletions

diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h b/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h
index d57282172ea5..c067b7888ac4 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h
+++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4.h
@@ -652,6 +652,7 @@ struct adapter {
         struct tid_info tids;
         void **tid_release_head;
         spinlock_t tid_release_lock;
+        struct workqueue_struct *workq;
         struct work_struct tid_release_task;
         struct work_struct db_full_task;
         struct work_struct db_drop_task;
diff --git a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c
index 1afee70ce856..18fb9c61d7ba 100644
--- a/drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c
+++ b/drivers/net/ethernet/chelsio/cxgb4/cxgb4_main.c
@@ -643,8 +643,6 @@ static int set_rxmode(struct net_device *dev, int mtu, bool sleep_ok)
         return ret;
 }
 
-static struct workqueue_struct *workq;
-
 /**
  *      link_start - enable a port
  *      @dev: the port to enable
@@ -3340,7 +3338,7 @@ static void cxgb4_queue_tid_release(struct tid_info *t, unsigned int chan,
         adap->tid_release_head = (void **)((uintptr_t)p | chan);
         if (!adap->tid_release_task_busy) {
                 adap->tid_release_task_busy = true;
-                queue_work(workq, &adap->tid_release_task);
+                queue_work(adap->workq, &adap->tid_release_task);
         }
         spin_unlock_bh(&adap->tid_release_lock);
 }
@@ -4140,7 +4138,7 @@ void t4_db_full(struct adapter *adap)
                 notify_rdma_uld(adap, CXGB4_CONTROL_DB_FULL);
                 t4_set_reg_field(adap, SGE_INT_ENABLE3,
                                  DBFIFO_HP_INT | DBFIFO_LP_INT, 0);
-                queue_work(workq, &adap->db_full_task);
+                queue_work(adap->workq, &adap->db_full_task);
         }
 }
 
@@ -4150,7 +4148,7 @@ void t4_db_dropped(struct adapter *adap)
                 disable_dbs(adap);
                 notify_rdma_uld(adap, CXGB4_CONTROL_DB_FULL);
         }
-        queue_work(workq, &adap->db_drop_task);
+        queue_work(adap->workq, &adap->db_drop_task);
 }
 
 static void uld_attach(struct adapter *adap, unsigned int uld)
@@ -6517,6 +6515,12 @@ static int init_one(struct pci_dev *pdev, const struct pci_device_id *ent)
                 goto out_disable_device;
         }
 
+        adapter->workq = create_singlethread_workqueue("cxgb4");
+        if (!adapter->workq) {
+                err = -ENOMEM;
+                goto out_free_adapter;
+        }
+
         /* PCI device has been enabled */
         adapter->flags |= DEV_ENABLED;
 
@@ -6715,6 +6719,9 @@ sriov:
  out_unmap_bar0:
         iounmap(adapter->regs);
  out_free_adapter:
+        if (adapter->workq)
+                destroy_workqueue(adapter->workq);
+
         kfree(adapter);
  out_disable_device:
         pci_disable_pcie_error_reporting(pdev);
@@ -6736,6 +6743,11 @@ static void remove_one(struct pci_dev *pdev)
         if (adapter) {
                 int i;
 
+                /* Tear down per-adapter Work Queue first since it can contain
+                 * references to our adapter data structure.
+                 */
+                destroy_workqueue(adapter->workq);
+
                 if (is_offload(adapter))
                         detach_ulds(adapter);
 
@@ -6788,20 +6800,14 @@ static int __init cxgb4_init_module(void)
 {
         int ret;
 
-        workq = create_singlethread_workqueue("cxgb4");
-        if (!workq)
-                return -ENOMEM;
-
         /* Debugfs support is optional, just warn if this fails */
         cxgb4_debugfs_root = debugfs_create_dir(KBUILD_MODNAME, NULL);
         if (!cxgb4_debugfs_root)
                 pr_warn("could not create debugfs entry, continuing\n");
 
         ret = pci_register_driver(&cxgb4_driver);
-        if (ret < 0) {
+        if (ret < 0)
                 debugfs_remove(cxgb4_debugfs_root);
-                destroy_workqueue(workq);
-        }
 
         register_inet6addr_notifier(&cxgb4_inet6addr_notifier);
 
@@ -6813,8 +6819,6 @@ static void __exit cxgb4_cleanup_module(void)
         unregister_inet6addr_notifier(&cxgb4_inet6addr_notifier);
         pci_unregister_driver(&cxgb4_driver);
         debugfs_remove(cxgb4_debugfs_root);  /* NULL ok */
-        flush_workqueue(workq);
-        destroy_workqueue(workq);
 }
 
 module_init(cxgb4_init_module);