bnxt_en: Don't cancel sp_task from bnxt_close_nic().

When implementing driver reset from tx_timeout in the next patch,
bnxt_close_nic() will be called from the sp_task workqueue.  Calling
cancel_work() on sp_task will hang the workqueue.

Instead, set a new bit BNXT_STATE_IN_SP_TASK when bnxt_sp_task() is running.
bnxt_close_nic() will wait for BNXT_STATE_IN_SP_TASK to clear before
proceeding.

Signed-off-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
index fd89e9d..f5f4489 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c
@@ -4679,7 +4679,9 @@
 	bnxt_tx_disable(bp);
 
 	clear_bit(BNXT_STATE_OPEN, &bp->state);
-	cancel_work_sync(&bp->sp_task);
+	smp_mb__after_atomic();
+	while (test_bit(BNXT_STATE_IN_SP_TASK, &bp->state))
+		msleep(20);
 
 	/* Flush rings before disabling interrupts */
 	bnxt_shutdown_nic(bp, irq_re_init);
@@ -5080,8 +5082,12 @@
 	struct bnxt *bp = container_of(work, struct bnxt, sp_task);
 	int rc;
 
-	if (!test_bit(BNXT_STATE_OPEN, &bp->state))
+	set_bit(BNXT_STATE_IN_SP_TASK, &bp->state);
+	smp_mb__after_atomic();
+	if (!test_bit(BNXT_STATE_OPEN, &bp->state)) {
+		clear_bit(BNXT_STATE_IN_SP_TASK, &bp->state);
 		return;
+	}
 
 	if (test_and_clear_bit(BNXT_RX_MASK_SP_EVENT, &bp->sp_event))
 		bnxt_cfg_rx_mode(bp);
@@ -5107,6 +5113,9 @@
 	}
 	if (test_and_clear_bit(BNXT_RESET_TASK_SP_EVENT, &bp->sp_event))
 		bnxt_reset_task(bp);
+
+	smp_mb__before_atomic();
+	clear_bit(BNXT_STATE_IN_SP_TASK, &bp->state);
 }
 
 static int bnxt_init_board(struct pci_dev *pdev, struct net_device *dev)
diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.h b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
index a8b6881..f199f4c 100644
--- a/drivers/net/ethernet/broadcom/bnxt/bnxt.h
+++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.h
@@ -927,6 +927,7 @@
 
 	unsigned long		state;
 #define BNXT_STATE_OPEN		0
+#define BNXT_STATE_IN_SP_TASK	1
 
 	struct bnxt_irq	*irq_tbl;
 	u8			mac_addr[ETH_ALEN];