net/mlx5_core: Call synchronize_irq() before freeing EQ buffer

After destroying the EQ, the object responsible for generating interrupts, call
synchronize_irq() to ensure that any handler routines running on other CPU
cores finish execution. Only then free the EQ buffer. This patch solves a very
rare case when we get panic on driver unload.
The same thing is done when we destroy a CQ which is one of the sources
generating interrupts. In the case of CQ we want to avoid completion handlers
on a CQ that was destroyed. In the case we do the same to avoid receiving
asynchronous events after the EQ has been destroyed and its buffers freed.

Signed-off-by: Eli Cohen <eli@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx5/core/eq.c

@@ -420,6 +420,7 @@ int mlx5_destroy_unmap_eq(struct mlx5_core_dev *dev, struct mlx5_eq *eq)
 	if (err)
 		mlx5_core_warn(dev, "failed to destroy a previously created eq: eqn %d\n",
 			       eq->eqn);
+	synchronize_irq(table->msix_arr[eq->irqn].vector);
 	mlx5_buf_free(dev, &eq->buf);
 
 	return err;