Add an cpsie i before the SVC call that starts the scheduler. This is just in case the C start up code leaves interrupts globally disabled.

Source/portable/GCC/ARM_CM3/port.c

@@ -155,7 +155,9 @@ void vPortStartFirstTask( void )
 					" ldr r0, [r0] 			\n"
 					" ldr r0, [r0] 			\n"
 					" msr msp, r0			\n" /* Set the msp back to the start of the stack. */
+					" cpsie i				\n"
 					" svc 0					\n" /* System call to start first task. */
+					" nop					\n"
 				);
 }
 /*-----------------------------------------------------------*/

Source/portable/IAR/ARM_CM3/portasm.s

@@ -33,9 +33,9 @@
     FreeRTOS is distributed in the hope that it will be useful, but WITHOUT
     ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
     FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
-    more details. You should have received a copy of the GNU General Public 
-    License and the FreeRTOS license exception along with FreeRTOS; if not it 
-    can be viewed here: http://www.freertos.org/a00114.html and also obtained 
+    more details. You should have received a copy of the GNU General Public
+    License and the FreeRTOS license exception along with FreeRTOS; if not it
+    can be viewed here: http://www.freertos.org/a00114.html and also obtained
     by writing to Richard Barry, contact details for whom are available on the
     FreeRTOS WEB site.
 
@@ -51,13 +51,6 @@
     licensing and training services.
 */
 
-/*
-	Change from V4.2.1:
-
-	+ Introduced usage of configKERNEL_INTERRUPT_PRIORITY macro to set the
-	  interrupt priority used by the kernel.
-*/
-
 #include <FreeRTOSConfig.h>
 
 /* For backward compatibility, ensure configKERNEL_INTERRUPT_PRIORITY is
@@ -157,6 +150,7 @@ vPortStartFirstTask
 	/* Set the msp back to the start of the stack. */
 	msr msp, r0
 	/* Call SVC to start the first task. */
+	cpsie i
 	svc 0
 
 	END

Source/portable/RVDS/ARM_CM3/port.c

@@ -149,7 +149,9 @@ __asm void vPortStartFirstTask( void )
 	/* Set the msp back to the start of the stack. */
 	msr msp, r0
 	/* Call SVC to start the first task. */
+	cpsie i
 	svc 0
+	nop
 }
 /*-----------------------------------------------------------*/