mlx4: Replacing pool_lock with mutex

Under the spinlock we call request_irq(), which allocates memory with GFP_KERNEL,
This causes the following trace when DEBUG_SPINLOCK is enabled, it can cause
the following trace:

 BUG: spinlock wrong CPU on CPU#2, ethtool/2595
 lock: ffff8801f9cbc2b0, .magic: dead4ead, .owner: ethtool/2595, .owner_cpu: 0
 Pid: 2595, comm: ethtool Not tainted 3.0.18 #2
 Call Trace:
 spin_bug+0xa2/0xf0
 do_raw_spin_unlock+0x71/0xa0
 _raw_spin_unlock+0xe/0x10
 mlx4_assign_eq+0x12b/0x190 [mlx4_core]
 mlx4_en_activate_cq+0x252/0x2d0 [mlx4_en]
 ? mlx4_en_activate_rx_rings+0x227/0x370 [mlx4_en]
 mlx4_en_start_port+0x189/0xb90 [mlx4_en]
 mlx4_en_set_ringparam+0x29a/0x340 [mlx4_en]
 dev_ethtool+0x816/0xb10
 ? dev_get_by_name_rcu+0xa4/0xe0
 dev_ioctl+0x2b5/0x470
 handle_mm_fault+0x1cd/0x2d0
 sock_do_ioctl+0x5d/0x70
 sock_ioctl+0x79/0x2f0
 do_vfs_ioctl+0x8c/0x340
 sys_ioctl+0xa1/0xb0
 system_call_fastpath+0x16/0x1b

Replacing with mutex, which is enough in this case.
Signed-off-by: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/eq.c

@@ -1036,7 +1036,7 @@ int mlx4_assign_eq(struct mlx4_dev *dev, char* name, int * vector)
 	struct mlx4_priv *priv = mlx4_priv(dev);
 	int vec = 0, err = 0, i;
 
-	spin_lock(&priv->msix_ctl.pool_lock);
+	mutex_lock(&priv->msix_ctl.pool_lock);
 	for (i = 0; !vec && i < dev->caps.comp_pool; i++) {
 		if (~priv->msix_ctl.pool_bm & 1ULL << i) {
 			priv->msix_ctl.pool_bm |= 1ULL << i;
@@ -1058,7 +1058,7 @@ int mlx4_assign_eq(struct mlx4_dev *dev, char* name, int * vector)
 			eq_set_ci(&priv->eq_table.eq[vec], 1);
 		}
 	}
-	spin_unlock(&priv->msix_ctl.pool_lock);
+	mutex_unlock(&priv->msix_ctl.pool_lock);
 
 	if (vec) {
 		*vector = vec;
@@ -1079,13 +1079,13 @@ void mlx4_release_eq(struct mlx4_dev *dev, int vec)
 	if (likely(i >= 0)) {
 		/*sanity check , making sure were not trying to free irq's
 		  Belonging to a legacy EQ*/
-		spin_lock(&priv->msix_ctl.pool_lock);
+		mutex_lock(&priv->msix_ctl.pool_lock);
 		if (priv->msix_ctl.pool_bm & 1ULL << i) {
 			free_irq(priv->eq_table.eq[vec].irq,
 				 &priv->eq_table.eq[vec]);
 			priv->msix_ctl.pool_bm &= ~(1ULL << i);
 		}
-		spin_unlock(&priv->msix_ctl.pool_lock);
+		mutex_unlock(&priv->msix_ctl.pool_lock);
 	}
 
 }

drivers/net/ethernet/mellanox/mlx4/main.c

@@ -1828,7 +1828,7 @@ static int __mlx4_init_one(struct pci_dev *pdev, const struct pci_device_id *id)
 		goto err_master_mfunc;
 
 	priv->msix_ctl.pool_bm = 0;
-	spin_lock_init(&priv->msix_ctl.pool_lock);
+	mutex_init(&priv->msix_ctl.pool_lock);
 
 	mlx4_enable_msi_x(dev);
 	if ((mlx4_is_mfunc(dev)) &&

drivers/net/ethernet/mellanox/mlx4/mlx4.h

@@ -697,7 +697,7 @@ struct mlx4_sense {
 
 struct mlx4_msix_ctl {
 	u64		pool_bm;
-	spinlock_t	pool_lock;
+	struct mutex	pool_lock;
 };
 
 struct mlx4_steer {