ibmvnic: Convert reset work item mutex to spin lock

ibmvnic_reset can create and schedule a reset work item from
an IRQ context, so do not use a mutex, which can sleep. Convert
the reset work item mutex to a spin lock. Locking debugger generated
the trace output below.

BUG: sleeping function called from invalid context at kernel/locking/mutex.c:908
in_atomic(): 1, irqs_disabled(): 1, pid: 120, name: kworker/8:1
4 locks held by kworker/8:1/120:
 #0: 0000000017c05720 ((wq_completion)"events"){+.+.}, at: process_one_work+0x188/0x710
 #1: 00000000ace90706 ((linkwatch_work).work){+.+.}, at: process_one_work+0x188/0x710
 #2: 000000007632871f (rtnl_mutex){+.+.}, at: rtnl_lock+0x30/0x50
 #3: 00000000fc36813a (&(&crq->lock)->rlock){..-.}, at: ibmvnic_tasklet+0x88/0x2010 [ibmvnic]
irq event stamp: 26293
hardirqs last  enabled at (26292): [<c000000000122468>] tasklet_action_common.isra.12+0x78/0x1c0
hardirqs last disabled at (26293): [<c000000000befce8>] _raw_spin_lock_irqsave+0x48/0xf0
softirqs last  enabled at (26288): [<c000000000a8ac78>] dev_deactivate_queue.constprop.28+0xc8/0x160
softirqs last disabled at (26289): [<c0000000000306e0>] call_do_softirq+0x14/0x24
CPU: 8 PID: 120 Comm: kworker/8:1 Kdump: loaded Not tainted 4.20.0-rc6 #6
Workqueue: events linkwatch_event
Call Trace:
[c0000003fffa7a50] [c000000000bc83e4] dump_stack+0xe8/0x164 (unreliable)
[c0000003fffa7aa0] [c00000000015ba0c] ___might_sleep+0x2dc/0x320
[c0000003fffa7b20] [c000000000be960c] __mutex_lock+0x8c/0xb40
[c0000003fffa7c30] [d000000006202ac8] ibmvnic_reset+0x78/0x330 [ibmvnic]
[c0000003fffa7cc0] [d0000000062097f4] ibmvnic_tasklet+0x1054/0x2010 [ibmvnic]
[c0000003fffa7e00] [c0000000001224c8] tasklet_action_common.isra.12+0xd8/0x1c0
[c0000003fffa7e60] [c000000000bf1238] __do_softirq+0x1a8/0x64c
[c0000003fffa7f90] [c0000000000306e0] call_do_softirq+0x14/0x24
[c0000003f3f87980] [c00000000001ba50] do_softirq_own_stack+0x60/0xb0
[c0000003f3f879c0] [c0000000001218a8] do_softirq+0xa8/0x100
[c0000003f3f879f0] [c000000000121a74] __local_bh_enable_ip+0x174/0x180
[c0000003f3f87a60] [c000000000bf003c] _raw_spin_unlock_bh+0x5c/0x80
[c0000003f3f87a90] [c000000000a8ac78] dev_deactivate_queue.constprop.28+0xc8/0x160
[c0000003f3f87ad0] [c000000000a8c8b0] dev_deactivate_many+0xd0/0x520
[c0000003f3f87b70] [c000000000a8cd40] dev_deactivate+0x40/0x60
[c0000003f3f87ba0] [c000000000a5e0c4] linkwatch_do_dev+0x74/0xd0
[c0000003f3f87bd0] [c000000000a5e694] __linkwatch_run_queue+0x1a4/0x1f0
[c0000003f3f87c30] [c000000000a5e728] linkwatch_event+0x48/0x60
[c0000003f3f87c50] [c0000000001444e8] process_one_work+0x238/0x710
[c0000003f3f87d20] [c000000000144a48] worker_thread+0x88/0x4e0
[c0000003f3f87db0] [c00000000014e3a8] kthread+0x178/0x1c0
[c0000003f3f87e20] [c00000000000bfd0] ret_from_kernel_thread+0x5c/0x6c
Signed-off-by: Thomas Falcon <tlfalcon@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/ibmvnic.c

@@ -1939,8 +1939,9 @@ static int do_hard_reset(struct ibmvnic_adapter *adapter,
 static struct ibmvnic_rwi *get_next_rwi(struct ibmvnic_adapter *adapter)
 {
 	struct ibmvnic_rwi *rwi;
+	unsigned long flags;
 
-	mutex_lock(&adapter->rwi_lock);
+	spin_lock_irqsave(&adapter->rwi_lock, flags);
 
 	if (!list_empty(&adapter->rwi_list)) {
 		rwi = list_first_entry(&adapter->rwi_list, struct ibmvnic_rwi,
@@ -1950,7 +1951,7 @@ static struct ibmvnic_rwi *get_next_rwi(struct ibmvnic_adapter *adapter)
 		rwi = NULL;
 	}
 
-	mutex_unlock(&adapter->rwi_lock);
+	spin_unlock_irqrestore(&adapter->rwi_lock, flags);
 	return rwi;
 }
 
@@ -2025,6 +2026,7 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
 	struct list_head *entry, *tmp_entry;
 	struct ibmvnic_rwi *rwi, *tmp;
 	struct net_device *netdev = adapter->netdev;
+	unsigned long flags;
 	int ret;
 
 	if (adapter->state == VNIC_REMOVING ||
@@ -2041,13 +2043,13 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
 		goto err;
 	}
 
-	mutex_lock(&adapter->rwi_lock);
+	spin_lock_irqsave(&adapter->rwi_lock, flags);
 
 	list_for_each(entry, &adapter->rwi_list) {
 		tmp = list_entry(entry, struct ibmvnic_rwi, list);
 		if (tmp->reset_reason == reason) {
 			netdev_dbg(netdev, "Skipping matching reset\n");
-			mutex_unlock(&adapter->rwi_lock);
+			spin_unlock_irqrestore(&adapter->rwi_lock, flags);
 			ret = EBUSY;
 			goto err;
 		}
@@ -2055,7 +2057,7 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
 
 	rwi = kzalloc(sizeof(*rwi), GFP_KERNEL);
 	if (!rwi) {
-		mutex_unlock(&adapter->rwi_lock);
+		spin_unlock_irqrestore(&adapter->rwi_lock, flags);
 		ibmvnic_close(netdev);
 		ret = ENOMEM;
 		goto err;
@@ -2069,7 +2071,7 @@ static int ibmvnic_reset(struct ibmvnic_adapter *adapter,
 	}
 	rwi->reset_reason = reason;
 	list_add_tail(&rwi->list, &adapter->rwi_list);
-	mutex_unlock(&adapter->rwi_lock);
+	spin_unlock_irqrestore(&adapter->rwi_lock, flags);
 	adapter->resetting = true;
 	netdev_dbg(adapter->netdev, "Scheduling reset (reason %d)\n", reason);
 	schedule_work(&adapter->ibmvnic_reset);
@@ -4759,7 +4761,7 @@ static int ibmvnic_probe(struct vio_dev *dev, const struct vio_device_id *id)
 
 	INIT_WORK(&adapter->ibmvnic_reset, __ibmvnic_reset);
 	INIT_LIST_HEAD(&adapter->rwi_list);
-	mutex_init(&adapter->rwi_lock);
+	spin_lock_init(&adapter->rwi_lock);
 	adapter->resetting = false;
 
 	adapter->mac_change_pending = false;

drivers/net/ethernet/ibm/ibmvnic.h

@@ -1075,7 +1075,7 @@ struct ibmvnic_adapter {
 	struct tasklet_struct tasklet;
 	enum vnic_state state;
 	enum ibmvnic_reset_reason reset_reason;
-	struct mutex rwi_lock;
+	spinlock_t rwi_lock;
 	struct list_head rwi_list;
 	struct work_struct ibmvnic_reset;
 	bool resetting;