CAN driver: Removing call to can_xmit() from can_txready() in a previous commit was a mistake. This commit restores the call to can_xmit(), but does the call in a safer environment on the work thread.

drivers/Kconfig

@@ -128,6 +128,7 @@ config CAN_NPENDINGRTR
 config CAN_TXREADY
 	bool "can_txready interface"
 	default n
+	select SCHED_WORKQUEUE
 	---help---
 		This selection enables the can_txready() interface.  This interface
 		is needed only for CAN hardware that supports queing of outgoing
@@ -173,6 +174,22 @@ config CAN_TXREADY
 		no longer full.  can_txready() will then awaken the
 		can_write() logic and the hang condition is avoided.
 
+choice
+	prompt "TX Ready Work Queue"
+	default CAN_TXREADY_LOPRI if SCHED_LPWORK
+	default CAN_TXREADY_HIPRI if !SCHED_LPWORK
+	depends on CAN_TXREADY
+
+config CAN_TXREADY_LOPRI
+	bool "Low-priority work queue"
+	select SCHED_LPWORK
+
+config CAN_TXREADY_HIPRI
+	bool "High-priority work queue"
+	select SCHED_HPWORK
+
+endchoice # TX Ready Work Queue
+
 config CAN_LOOPBACK
 	bool "CAN loopback mode"
 	default n