[PATCH 5/7] ibmvnic: use a lock to serialize remove/reset

[Sukadev Bhattiprolu]

Use a separate lock to serialze ibmvnic_reset() and ibmvnic_remove()
functions. ibmvnic_reset() schedules work for the worker thread and
ibmvnic_remove() flushes the work before removing the adapter. We
don't want any work to be scheduled once we start removing the
adapter (i.e after we have already flushed the work).

A follow-on patch will convert the ->state_lock from a spinklock
to a mutex to allow us to hold it for longer periods of time.
ibmvnic_reset() can be called from a tasklet and cannot use the
mutex.

Fixes: 6954a9e4192b ("ibmvnic: Flush existing work items before
                     device removal")

Signed-off-by: Sukadev Bhattiprolu <suka...@linux.ibm.com>
---
 drivers/net/ethernet/ibm/ibmvnic.c | 16 +++++++++++++++-
 drivers/net/ethernet/ibm/ibmvnic.h |  2 ++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ibm/ibmvnic.c 
b/drivers/net/ethernet/ibm/ibmvnic.c
index ad551418ac63..c7675ab0b7e3 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.c
+++ b/drivers/net/ethernet/ibm/ibmvnic.c
@@ -2435,6 +2435,7 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
                         enum ibmvnic_reset_reason reason)
 {
        struct net_device *netdev = adapter->netdev;
+       unsigned long rmflags;
        int ret;
 
        if (adapter->state == VNIC_PROBING) {
@@ -2443,6 +2444,8 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
                goto err;
        }
 
+       spin_lock_irqsave(&adapter->remove_lock, rmflags);
+
        /*
         * If failover is pending don't schedule any other reset.
         * Instead let the failover complete. If there is already a
@@ -2465,8 +2468,9 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
        netdev_dbg(adapter->netdev, "Scheduling reset (reason %d)\n", reason);
        schedule_work(&adapter->ibmvnic_reset);
 
-       return 0;
+       ret = 0;
 err:
+       spin_unlock_irqrestore(&adapter->remove_lock, rmflags);
        return -ret;
 }
 
@@ -5387,6 +5391,7 @@ static int ibmvnic_probe(struct vio_dev *dev, const 
struct vio_device_id *id)
        memset(&adapter->pending_resets, 0, sizeof(adapter->pending_resets));
        spin_lock_init(&adapter->rwi_lock);
        spin_lock_init(&adapter->state_lock);
+       spin_lock_init(&adapter->remove_lock);
        mutex_init(&adapter->fw_lock);
        init_completion(&adapter->init_done);
        init_completion(&adapter->fw_done);
@@ -5459,6 +5464,7 @@ static int ibmvnic_remove(struct vio_dev *dev)
 {
        struct net_device *netdev = dev_get_drvdata(&dev->dev);
        struct ibmvnic_adapter *adapter = netdev_priv(netdev);
+       unsigned long rmflags;
        unsigned long flags;
 
        spin_lock_irqsave(&adapter->state_lock, flags);
@@ -5467,7 +5473,15 @@ static int ibmvnic_remove(struct vio_dev *dev)
                return -EBUSY;
        }
 
+       /* If ibmvnic_reset() is scheduling a reset, wait for it to
+        * finish. Then prevent it from scheduling any more resets
+        * and have the reset functions ignore any resets that have
+        * already been scheduled.
+        */
+       spin_lock_irqsave(&adapter->remove_lock, rmflags);
        adapter->state = VNIC_REMOVING;
+       spin_unlock_irqrestore(&adapter->remove_lock, rmflags);
+
        spin_unlock_irqrestore(&adapter->state_lock, flags);
 
        flush_work(&adapter->ibmvnic_reset);
diff --git a/drivers/net/ethernet/ibm/ibmvnic.h 
b/drivers/net/ethernet/ibm/ibmvnic.h
index 1179a95a3f92..2779696ade09 100644
--- a/drivers/net/ethernet/ibm/ibmvnic.h
+++ b/drivers/net/ethernet/ibm/ibmvnic.h
@@ -1081,6 +1081,8 @@ struct ibmvnic_adapter {
        spinlock_t rwi_lock;
        enum ibmvnic_reset_reason pending_resets[VNIC_RESET_MAX-1];
        short next_reset;
+       /* serialize ibmvnic_reset() and ibmvnic_remove() */
+       spinlock_t remove_lock;
        struct work_struct ibmvnic_reset;
        struct delayed_work ibmvnic_delayed_reset;
        unsigned long resetting;
-- 
2.26.2