Implement deferred IRQ locking. Adds partial support for Xtensa. More is needed.

arch/xtensa/src/common/xtensa_irqdispatch.c

@@ -52,6 +52,7 @@
 
 #include "group/group.h"
 #include "sched/sched.h"
+#include "irq/irq.h"
 
 /****************************************************************************
  * Public Functions
@@ -129,6 +130,17 @@ uint32_t *xtensa_irq_dispatch(int irq, uint32_t *regs)
 
       (void)group_addrenv(NULL);
 #endif
+
+#ifdef CONFIG_SMP
+      /* In the SMP configuration, critical section management uses a
+       * "voting" algorithm with current task on each CPU casting its
+       * "vote" by the state of the TCB irqcount flag.  That irqcount
+       * for the current task on this CPU will be different is a
+       * context switch occurrred.
+       */
+
+      irq_restore_lock();
+#endif
     }
 #endif