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

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Date:   Thu,  7 Jan 2021 23:12:34 -0800
From:   Sukadev Bhattiprolu <sukadev@...ux.ibm.com>
To:     netdev@...r.kernel.org
Cc:     Dany Madden <drt@...ux.ibm.com>, Lijun Pan <ljp@...ux.ibm.com>,
        sukadev@...ux.ibm.com
Subject: [PATCH 5/7] ibmvnic: use a lock to serialize remove/reset

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 <sukadev@...ux.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