A little optimisation.

Source/portable/MPLAB/PIC32MX/port.c

@@ -167,19 +167,6 @@ extern void *pxCurrentTCB;
 }
 /*-----------------------------------------------------------*/
 
-void vPortYield( void )
-{
-unsigned portLONG ulStatus;
-
-	SetCoreSW0();
-
-	/* Unmask all interrupts. */
-	ulStatus = _CP0_GET_STATUS();
-	ulStatus &= ~portALL_IPL_BITS;
-	_CP0_SET_STATUS( ulStatus );
-}
-/*-----------------------------------------------------------*/
-
 void vPortIncrementTick( void )
 {
 unsigned portBASE_TYPE uxSavedStatus;

Source/portable/MPLAB/PIC32MX/port_asm.S

@@ -51,7 +51,6 @@
 #include <sys/asm.h>
 #include "ISR_Support.h"
  
-#define portEXC_CODE_MASK ( 0x1f << 2 )
 
 	.set	nomips16
  	.set 	noreorder
@@ -138,10 +137,9 @@ vPortYieldISR:
 	la			sp, xISRStackTop
 	lw			sp, (sp)
 
-	/* Increment and save the nesting count in case this gets preempted. */
+	/* Set the nesting count. */
 	la			k0, uxInterruptNesting
-	lw			s6, (k0)
-	addiu		s6, s6, 1
+	addiu		s6, zero, 1
 	sw			s6, 0(k0)
 
 	/* s6 holds the EPC value, this is saved with the rest of the context
@@ -261,11 +259,10 @@ vPortYieldISR:
 	/* Protect access to the k registers, and others. */
 	di
 
-	/* Decrement the nesting count. */
+	/* Set nesting back to zero.  As the lowest priority interrupt this
+	interrupt cannot have nested. */
 	la			k0, uxInterruptNesting
-	lw			k1, (k0)
-	addiu		k1, k1, -1
-	sw			k1, 0(k0)
+	sw			zero, 0(k0)
 
 	/* Switch back to use the real stack pointer. */
 	add			sp, zero, s5
@@ -273,8 +270,7 @@ vPortYieldISR:
 	/* Restore the real s5 value. */
 	lw			s5, 40(sp)
 
-	/* If the critical nesting is not zero and a yield is not pended
-	then set status as if within a critical section. */
+	/* Pop the status and epc values. */
 	lw			k1, portSTATUS_STACK_LOCATION(sp)
 	lw			k0, portEPC_STACK_LOCATION(sp)
 

Source/portable/MPLAB/PIC32MX/portmacro.h

@@ -94,6 +94,7 @@ extern "C" {
 /* Critical section management. */
 #define portIPL_SHIFT				( 10 )
 #define portALL_IPL_BITS			( 0x3f << portIPL_SHIFT )
+#define portSW0_BIT					( 0x01 << 8 )
 
 #define portDISABLE_INTERRUPTS()											\
 {																			\
@@ -130,10 +131,19 @@ extern void vPortClearInterruptMaskFromISR( unsigned portBASE_TYPE );
 /*-----------------------------------------------------------*/
 
 /* Task utilities. */
-extern void vPortYield( void );
-#define portYIELD()	vPortYield()
 
-#define portNOP()				asm volatile ( 	"nop" )
+#define portYIELD()								\
+{												\
+unsigned portLONG ulStatus;						\
+												\
+	/* Unmask all interrupts. */				\
+	ulStatus = _CP0_GET_CAUSE();				\
+	ulStatus |= portSW0_BIT;					\
+	_CP0_SET_CAUSE( ulStatus );					\
+}
+
+
+#define portNOP()	asm volatile ( 	"nop" )
 
 /*-----------------------------------------------------------*/