current_regs should be volatile; add support for nested interrupts; enable interrupts during syscall processing

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@3475 42af7a65-404d-4744-a932-0658087f49c3

56 files changed, 303 insertions, 148 deletions

diff --git a/apps/netutils/thttpd/Makefile b/apps/netutils/thttpd/Makefile
index ec0df4ba6..963ab514f 100644
--- a/apps/netutils/thttpd/Makefile
+++ b/apps/netutils/thttpd/Makefile
@@ -69,9 +69,15 @@ SUBDIR_BIN3	= ssi
 SUBDIR_BIN	+= cgi-bin/$(SUBDIR_BIN1) cgi-bin/$(SUBDIR_BIN2)  cgi-bin/$(SUBDIR_BIN3)
 endif
 
-all: $(SUBDIR_BIN) $(BIN)
+all: $(SUBDIR_BIN) .built
 .PHONY: depend clean distclean
 
+$(AOBJS): %$(OBJEXT): %.S
+	$(call ASSEMBLE, $<, $@)
+
+$(COBJS): %$(OBJEXT): %.c
+	$(call COMPILE, $<, $@)
+
 ifeq ($(CONFIG_NXFLAT),y)
 cgi-bin:
 	@mkdir cgi-bin
@@ -97,12 +103,10 @@ endif
 
 .built: $(OBJS)
 	@( for obj in $(OBJS) ; do \
-		$(call ARCHIVE, $@, $${obj}); \
+		$(call ARCHIVE, $(BIN), $${obj}); \
 	done ; )
 	@touch .built
 	
-.built: $(BIN)
-
 context:
 
 .depend: Makefile $(SRCS)
diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index 2605cf699..5ad9eaaf0 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -1653,6 +1653,11 @@
 	  an up_initialize() provide the same kind of capability.
 	* arch/*/include/*/type.h: On some compilers, char defaults as unsigned.
 	  Explicitly add signed to integer types if signed is what is required.
+	* arch/*: For all architectures -- Global register state save structure
+	  (usually called current_regs) should be marked volatile; Added general
+	  capability to support nested interrupts (not fully realized for all
+	  architectures).
+
 
 
 
diff --git a/nuttx/arch/8051/src/up_initialize.c b/nuttx/arch/8051/src/up_initialize.c
index 3f0bc4027..4252dd617 100644
--- a/nuttx/arch/8051/src/up_initialize.c
+++ b/nuttx/arch/8051/src/up_initialize.c
@@ -1,7 +1,7 @@
 /************************************************************************
  * up_initialize.c
  *
- *   Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -61,7 +61,7 @@
  * interrupt.
  */
 
-uint8_t g_irqtos;
+volatile uint8_t g_irqtos;
 
 /* Registers are saved in the following global array during
  * interrupt processing.  If a context switch is performed
diff --git a/nuttx/arch/8051/src/up_internal.h b/nuttx/arch/8051/src/up_internal.h
index d49c757a6..75fe58c40 100644
--- a/nuttx/arch/8051/src/up_internal.h
+++ b/nuttx/arch/8051/src/up_internal.h
@@ -1,7 +1,7 @@
 /**************************************************************************
  * up_internal.h
  *
- *   Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -72,7 +72,7 @@
  * interrupt.
  */
 
-extern uint8_t g_irqtos;
+extern volatile uint8_t g_irqtos;
 
 /* Registers are saved in the following global array during
  * interrupt processing.  If a context switch is performed
diff --git a/nuttx/arch/8051/src/up_irqtest.c b/nuttx/arch/8051/src/up_irqtest.c
index b0bdc8464..211f7e05f 100644
--- a/nuttx/arch/8051/src/up_irqtest.c
+++ b/nuttx/arch/8051/src/up_irqtest.c
@@ -1,7 +1,7 @@
 /************************************************************************
  * up_irqtest.c
  *
- *   Copyright (C) 2007 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -68,10 +68,10 @@ typedef void (*vector_t)(void);
  * Public Variables
  ************************************************************************/
 
-bool    g_irqtest;
-uint8_t g_irqtos;
+bool g_irqtest;
+volatile uint8_t g_irqtos;
 uint8_t g_irqregs[REGS_SIZE];
-int     g_nirqs;
+int g_nirqs;
 FAR struct xcptcontext *g_irqcontext; 
 
 /************************************************************************
diff --git a/nuttx/arch/arm/include/cortexm3/irq.h b/nuttx/arch/arm/include/cortexm3/irq.h
index 5c9ef04c0..063568655 100644
--- a/nuttx/arch/arm/include/cortexm3/irq.h
+++ b/nuttx/arch/arm/include/cortexm3/irq.h
@@ -156,6 +156,13 @@ struct xcptcontext
 
 #ifndef __ASSEMBLY__
 
+/* Disable IRQs */
+
+static inline void irqdisable(void)
+{
+  __asm__ __volatile__ ("\tcpsid  i\n");
+}
+
 /* Save the current primask state & disable IRQs */
 
 static inline irqstate_t irqsave(void)
@@ -176,6 +183,13 @@ static inline irqstate_t irqsave(void)
   return primask;
 }
 
+/* Enable IRQs */
+
+static inline void irqenable(void)
+{
+  __asm__ __volatile__ ("\tcpsie  i\n");
+}
+
 /* Restore saved primask state */
 
 static inline void irqrestore(irqstate_t primask)
diff --git a/nuttx/arch/arm/src/arm/up_dataabort.c b/nuttx/arch/arm/src/arm/up_dataabort.c
index 05886e384..c36970c1b 100644
--- a/nuttx/arch/arm/src/arm/up_dataabort.c
+++ b/nuttx/arch/arm/src/arm/up_dataabort.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/arm/up_dataabort.c
  *
- *   Copyright (C) 2007-2010 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -103,13 +103,19 @@
 void up_dataabort(uint32_t *regs, uint32_t far, uint32_t fsr)
 {
   FAR _TCB *tcb = (FAR _TCB *)g_readytorun.head;
+#ifdef CONFIG_PAGING
+   uint32_t *savestate;
 
   /* Save the saved processor context in current_regs where it can be accessed
    * for register dumps and possibly context switching.
    */
 
+
+  savestate    = (uint32_t*)current_regs;
+#endif
   current_regs = regs;
 
+#ifdef CONFIG_PAGING
   /* In the NuttX on-demand paging implementation, only the read-only, .text
    * section is paged.  However, the ARM compiler generated PC-relative data
    * fetches from within the .text sections.  Also, it is customary to locate
@@ -162,12 +168,16 @@ void up_dataabort(uint32_t *regs, uint32_t far, uint32_t fsr)
 
   pg_miss();
 
-  /* Indicate that we are no longer in an interrupt handler */
+  /* Restore the previous value of current_regs.  NULL would indicate that
+   * we are no longer in an interrupt handler.  It will be non-NULL if we
+   * are returning from a nested interrupt.
+   */
 
-  current_regs = NULL;
+  current_regs = savestate;
   return;
 
 segfault:
+#endif
   lldbg("Data abort. PC: %08x FAR: %08x FSR: %08x\n", regs[REG_PC], far, fsr);
   PANIC(OSERR_ERREXCEPTION);
 }
diff --git a/nuttx/arch/arm/src/arm/up_doirq.c b/nuttx/arch/arm/src/arm/up_doirq.c
index 5c127b75c..1f1c77473 100644
--- a/nuttx/arch/arm/src/arm/up_doirq.c
+++ b/nuttx/arch/arm/src/arm/up_doirq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/arm/up_doirq.c
  *
- *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -76,6 +76,8 @@ void up_doirq(int irq, uint32_t *regs)
 #ifdef CONFIG_SUPPRESS_INTERRUPTS
   PANIC(OSERR_ERREXCEPTION);
 #else
+  uint32_t *savestate;
+
   /* Nested interrupts are not supported in this implementation.  If you want
    * implemented nested interrupts, you would have to (1) change the way that
    * current regs is handled and (2) the design associated with
@@ -86,7 +88,7 @@ void up_doirq(int irq, uint32_t *regs)
    * current_regs is also used to manage interrupt level context switches.
    */
 
-  DEBUGASSERT(current_regs == NULL);
+  savestate    = (uint32_t*)current_regs;
   current_regs = regs;
 
   /* Mask and acknowledge the interrupt */
@@ -97,9 +99,12 @@ void up_doirq(int irq, uint32_t *regs)
 
   irq_dispatch(irq, regs);
 
-  /* Indicate that we are no long in an interrupt handler */
+  /* Restore the previous value of current_regs.  NULL would indicate that
+   * we are no longer in an interrupt handler.  It will be non-NULL if we
+   * are returning from a nested interrupt.
+   */
 
-  current_regs = NULL;
+  current_regs = savestate;
 
   /* Unmask the last interrupt (global interrupts are still disabled) */
 
diff --git a/nuttx/arch/arm/src/arm/up_prefetchabort.c b/nuttx/arch/arm/src/arm/up_prefetchabort.c
index 2d184bad6..ed3dd91d3 100644
--- a/nuttx/arch/arm/src/arm/up_prefetchabort.c
+++ b/nuttx/arch/arm/src/arm/up_prefetchabort.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  *  arch/arm/src/src/up_prefetchabort.c
  *
- *   Copyright (C) 2007-2010 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -89,10 +89,15 @@
 
 void up_prefetchabort(uint32_t *regs)
 {
+#ifdef CONFIG_PAGING
+   uint32_t *savestate;
+
   /* Save the saved processor context in current_regs where it can be accessed
    * for register dumps and possibly context switching.
    */
 
+  savestate    = (uint32_t*)current_regs;
+#endif
   current_regs = regs;
 
 #ifdef CONFIG_PAGING
@@ -133,9 +138,12 @@ void up_prefetchabort(uint32_t *regs)
 
       pg_miss();
 
-      /* Indicate that we are no longer in an interrupt handler */
+      /* Restore the previous value of current_regs.  NULL would indicate that
+       * we are no longer in an interrupt handler.  It will be non-NULL if we
+       * are returning from a nested interrupt.
+       */
 
-      current_regs = NULL;
+      current_regs = savestate;
     }
   else
 #endif
diff --git a/nuttx/arch/arm/src/c5471/c5471_irq.c b/nuttx/arch/arm/src/c5471/c5471_irq.c
index 6906e8f8d..fbeb2e720 100644
--- a/nuttx/arch/arm/src/c5471/c5471_irq.c
+++ b/nuttx/arch/arm/src/c5471/c5471_irq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/c5471/c5471_irq.c
  *
- *   Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -59,7 +59,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/common/up_internal.h b/nuttx/arch/arm/src/common/up_internal.h
index 9fe4464c7..803a6563d 100644
--- a/nuttx/arch/arm/src/common/up_internal.h
+++ b/nuttx/arch/arm/src/common/up_internal.h
@@ -82,11 +82,11 @@
  */
 
 #ifdef CONFIG_ARCH_CORTEXM3
-#  define up_savestate(regs)    up_copystate(regs, current_regs)
+#  define up_savestate(regs)    up_copystate(regs, (uint32_t*)current_regs)
 #  define up_restorestate(regs) (current_regs = regs)
 #else
-#  define up_savestate(regs)    up_copystate(regs, current_regs)
-#  define up_restorestate(regs) up_copystate(current_regs, regs)
+#  define up_savestate(regs)    up_copystate(regs, (uint32_t*)current_regs)
+#  define up_restorestate(regs) up_copystate((uint32_t*)current_regs, regs)
 #endif
 
 /****************************************************************************
@@ -107,7 +107,7 @@ typedef void (*up_vector_t)(void);
  * interrupt processing.
  */
 
-extern uint32_t *current_regs;
+extern volatile uint32_t *current_regs;
 
 /* This is the beginning of heap as provided from up_head.S.
  * This is the first address in DRAM after the loaded
diff --git a/nuttx/arch/arm/src/cortexm3/up_doirq.c b/nuttx/arch/arm/src/cortexm3/up_doirq.c
index d5f3a6185..fc2f75c97 100644
--- a/nuttx/arch/arm/src/cortexm3/up_doirq.c
+++ b/nuttx/arch/arm/src/cortexm3/up_doirq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/cortexm3/up_doirq.c
  *
- *   Copyright (C) 2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -76,6 +76,8 @@ uint32_t *up_doirq(int irq, uint32_t *regs)
 #ifdef CONFIG_SUPPRESS_INTERRUPTS
   PANIC(OSERR_ERREXCEPTION);
 #else
+  uint32_t *savestate;
+
   /* Nested interrupts are not supported in this implementation.  If you want
    * implemented nested interrupts, you would have to (1) change the way that
    * current regs is handled and (2) the design associated with
@@ -86,7 +88,7 @@ uint32_t *up_doirq(int irq, uint32_t *regs)
    * current_regs is also used to manage interrupt level context switches.
    */
 
-  DEBUGASSERT(current_regs == NULL);
+  savestate     = (uint32_t*)current_regs;
   current_regs = regs;
 
   /* Mask and acknowledge the interrupt */
@@ -103,11 +105,14 @@ uint32_t *up_doirq(int irq, uint32_t *regs)
    * switch occurred during interrupt processing.
    */
 
-  regs = current_regs;
+  regs = (uint32_t*)current_regs;
 
-  /* Indicate that we are no long in an interrupt handler */
+  /* Restore the previous value of current_regs.  NULL would indicate that
+   * we are no longer in an interrupt handler.  It will be non-NULL if we
+   * are returning from a nested interrupt.
+   */
 
-  current_regs = NULL;
+  current_regs = savestate;
 
   /* Unmask the last interrupt (global interrupts are still disabled) */
 
diff --git a/nuttx/arch/arm/src/cortexm3/up_svcall.c b/nuttx/arch/arm/src/cortexm3/up_svcall.c
index ec67617a7..f7e55a98b 100644
--- a/nuttx/arch/arm/src/cortexm3/up_svcall.c
+++ b/nuttx/arch/arm/src/cortexm3/up_svcall.c
@@ -57,7 +57,20 @@
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
+/* Configuration ************************************************************/
+
+#undef SYSCALL_INTERRUPTIBLE
+#if defined(CONFIG_NUTTX_KERNEL)
+#  if CONFIG_ARCH_INTERRUPTSTACK > 3
+#    warning "CONFIG_ARCH_INTERRUPTSTACK and CONFIG_NUTTX_KERNEL are incompatible"
+#    warning "options as currently implemented.  Interrupts will have to be disabled"
+#    warning "during SYScall processing to avoid un-handled nested interrupts"
+#  else
+#    define SYSCALL_INTERRUPTIBLE 1
+#  endif
+#endif
 
+/* Debug ********************************************************************/
 /* Debug output from this file may interfere with context switching!  To get
  * debug output you must enabled the following in your NuttX configuration:
  *
@@ -116,6 +129,12 @@ static inline void dispatch_syscall(uint32_t *regs)
 
       int index = cmd - CONFIG_SYS_RESERVED;
 
+      /* Enable interrupts while the SYSCALL executes */
+
+#ifdef SYSCALL_INTERRUPTIBLE
+      irqenable();
+#endif
+
       /* Call the correct stub for each SYS call, based on the number of parameters */
 
       svcdbg("Calling stub%d at %p\n", index, g_stubloopkup[index].stub0);
@@ -177,6 +196,10 @@ static inline void dispatch_syscall(uint32_t *regs)
                  cmd, g_stubnparms[index]);
           break;
         }
+
+#ifdef SYSCALL_INTERRUPTIBLE
+      irqdisable();
+#endif
     }
 
   /* Set up the return vaue.  First, check if a context switch occurred. 
diff --git a/nuttx/arch/arm/src/dm320/dm320_decodeirq.c b/nuttx/arch/arm/src/dm320/dm320_decodeirq.c
index a844fcae9..cb3efa5b9 100644
--- a/nuttx/arch/arm/src/dm320/dm320_decodeirq.c
+++ b/nuttx/arch/arm/src/dm320/dm320_decodeirq.c
@@ -2,7 +2,7 @@
  * arch/arm/src/dm320/dm320_decodeirq.c
  * arch/arm/src/chip/dm320_decodeirq.c
  *
- *   Copyright (C) 2007, 2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007, 2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -94,6 +94,8 @@ void up_decodeirq(uint32_t* regs)
 
       if ((unsigned)irq < NR_IRQS)
         {
+          uint32_t *savestate;
+
           /* Mask and acknowledge the interrupt */
 
           up_maskack_irq(irq);
@@ -102,15 +104,19 @@ void up_decodeirq(uint32_t* regs)
            * current_regs is also used to manage interrupt level context switches.
            */
 
+          savestate    = (uint32_t*)current_regs;
           current_regs = regs;
 
           /* Deliver the IRQ */
 
           irq_dispatch(irq, regs);
 
-          /* Indicate that we are no longer in an interrupt handler */
+          /* Restore the previous value of current_regs.  NULL would indicate that
+           * we are no longer in an interrupt handler.  It will be non-NULL if we
+           * are returning from a nested interrupt.
+           */
 
-          current_regs = NULL;
+          current_regs = savestate;
 
           /* Unmask the last interrupt (global interrupts are still
            * disabled).
diff --git a/nuttx/arch/arm/src/dm320/dm320_irq.c b/nuttx/arch/arm/src/dm320/dm320_irq.c
index f094bab1c..eb8201bb4 100644
--- a/nuttx/arch/arm/src/dm320/dm320_irq.c
+++ b/nuttx/arch/arm/src/dm320/dm320_irq.c
@@ -57,7 +57,7 @@
  * Public Data
  ************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/imx/imx_decodeirq.c b/nuttx/arch/arm/src/imx/imx_decodeirq.c
index 96a40fd4a..55c72ed76 100644
--- a/nuttx/arch/arm/src/imx/imx_decodeirq.c
+++ b/nuttx/arch/arm/src/imx/imx_decodeirq.c
@@ -2,7 +2,7 @@
  * arch/arm/src/imx/imx_decodeirq.c
  * arch/arm/src/chip/imx_decodeirq.c
  *
- *   Copyright (C) 2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -78,6 +78,7 @@ void up_decodeirq(uint32_t* regs)
   current_regs = regs;
   PANIC(OSERR_ERREXCEPTION);
 #else
+  uint32_t* savestate;
   uint32_t regval;
   int irq;
 
@@ -85,6 +86,7 @@ void up_decodeirq(uint32_t* regs)
    * current_regs is also used to manage interrupt level context switches.
    */
 
+  savestate    = (uint32_t*)current_regs;
   current_regs = regs;
 
   /* Loop while there are pending interrupts to be processed */
@@ -124,8 +126,11 @@ void up_decodeirq(uint32_t* regs)
     }
   while (irq < NR_IRQS);
 
-  /* Indicate that we are no longer in an interrupt handler */
+  /* Restore the previous value of current_regs.  NULL would indicate that
+   * we are no longer in an interrupt handler.  It will be non-NULL if we
+   * are returning from a nested interrupt.
+   */
 
-  current_regs = NULL;
+  current_regs = savestate;
 #endif
 }
diff --git a/nuttx/arch/arm/src/imx/imx_irq.c b/nuttx/arch/arm/src/imx/imx_irq.c
index b346064c5..934a60f0b 100644
--- a/nuttx/arch/arm/src/imx/imx_irq.c
+++ b/nuttx/arch/arm/src/imx/imx_irq.c
@@ -2,7 +2,7 @@
  * arch/arm/src/imc/imx_irq.c
  * arch/arm/src/chip/imx_irq.c
  *
- *   Copyright (C) 2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -56,7 +56,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/lm3s/lm3s_irq.c b/nuttx/arch/arm/src/lm3s/lm3s_irq.c
index da7f3d9c3..915ce3d13 100644
--- a/nuttx/arch/arm/src/lm3s/lm3s_irq.c
+++ b/nuttx/arch/arm/src/lm3s/lm3s_irq.c
@@ -75,7 +75,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/lpc17xx/lpc17_irq.c b/nuttx/arch/arm/src/lpc17xx/lpc17_irq.c
index 967de45d7..cf3467833 100755
--- a/nuttx/arch/arm/src/lpc17xx/lpc17_irq.c
+++ b/nuttx/arch/arm/src/lpc17xx/lpc17_irq.c
@@ -75,7 +75,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/lpc214x/lpc214x_decodeirq.c b/nuttx/arch/arm/src/lpc214x/lpc214x_decodeirq.c
index dc76509a9..6317066c3 100644
--- a/nuttx/arch/arm/src/lpc214x/lpc214x_decodeirq.c
+++ b/nuttx/arch/arm/src/lpc214x/lpc214x_decodeirq.c
@@ -1,7 +1,7 @@
 /********************************************************************************
  * arch/arm/src/lpc214x/lpc214x_decodeirq.c
  *
- *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -145,19 +145,25 @@ static void lpc214x_decodeirq( uint32_t *regs)
 
   if (irq < NR_IRQS)
     {
+      uint32_t *savestate;
+
       /* Current regs non-zero indicates that we are processing an interrupt;
        * current_regs is also used to manage interrupt level context switches.
        */
 
+      savestate    = (uint32_t*)current_regs;
       current_regs = regs;
 
       /* Deliver the IRQ */
 
       irq_dispatch(irq, regs);
 
-      /* Indicate that we are no long in an interrupt handler */
+      /* Restore the previous value of current_regs.  NULL would indicate that
+       * we are no longer in an interrupt handler.  It will be non-NULL if we
+       * are returning from a nested interrupt.
+       */
 
-      current_regs = NULL;
+      current_regs = savestate;
     }
 #endif
 }
diff --git a/nuttx/arch/arm/src/lpc214x/lpc214x_irq.c b/nuttx/arch/arm/src/lpc214x/lpc214x_irq.c
index 9d8ed817b..a8b91037c 100644
--- a/nuttx/arch/arm/src/lpc214x/lpc214x_irq.c
+++ b/nuttx/arch/arm/src/lpc214x/lpc214x_irq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/lpc214x/lpc214x_irq.c
  *
- *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -59,7 +59,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/lpc2378/lpc23xx_decodeirq.c b/nuttx/arch/arm/src/lpc2378/lpc23xx_decodeirq.c
index 42b678432..100502a22 100755
--- a/nuttx/arch/arm/src/lpc2378/lpc23xx_decodeirq.c
+++ b/nuttx/arch/arm/src/lpc2378/lpc23xx_decodeirq.c
@@ -6,7 +6,7 @@
  *
  * This file is part of the NuttX RTOS and based on the lpc2148 port:
  *
- *   Copyright (C) 2010 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2010, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -131,11 +131,13 @@ static void lpc23xx_decodeirq(uint32_t *regs)
 
   if (irq < NR_IRQS)            /* redundant check ?? */
     {
+       uint32_t *savestate;
+
       /* Current regs non-zero indicates that we are processing an interrupt;
        * current_regs is also used to manage interrupt level context switches.
        */
 
-      DEBUGASSERT(current_regs == NULL);
+      savestate    = (uint32_t*)current_regs;
       current_regs = regs;
 
       /* Mask and acknowledge the interrupt */
@@ -146,9 +148,12 @@ static void lpc23xx_decodeirq(uint32_t *regs)
 
       irq_dispatch(irq, regs);
 
-      /* Indicate that we are no longer in an interrupt handler */
+      /* Restore the previous value of current_regs.  NULL would indicate that
+       * we are no longer in an interrupt handler.  It will be non-NULL if we
+       * are returning from a nested interrupt.
+       */
 
-      current_regs = NULL;
+      current_regs = savestate;
     }
 
 #endif
diff --git a/nuttx/arch/arm/src/lpc2378/lpc23xx_irq.c b/nuttx/arch/arm/src/lpc2378/lpc23xx_irq.c
index 9a6268a2f..10f188cba 100755
--- a/nuttx/arch/arm/src/lpc2378/lpc23xx_irq.c
+++ b/nuttx/arch/arm/src/lpc2378/lpc23xx_irq.c
@@ -65,7 +65,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/lpc313x/lpc313x_decodeirq.c b/nuttx/arch/arm/src/lpc313x/lpc313x_decodeirq.c
index 9abaff3c1..119e65c50 100755
--- a/nuttx/arch/arm/src/lpc313x/lpc313x_decodeirq.c
+++ b/nuttx/arch/arm/src/lpc313x/lpc313x_decodeirq.c
@@ -102,6 +102,8 @@ void up_decodeirq(uint32_t *regs)
 
       if ((unsigned)irq < NR_IRQS)
         {
+          uint32_t* savestate;
+
           /* Mask and acknowledge the interrupt */
 
           up_maskack_irq(irq);
@@ -110,15 +112,19 @@ void up_decodeirq(uint32_t *regs)
            * current_regs is also used to manage interrupt level context switches.
            */
 
+          savestate    = (uint32_t*)current_regs;
           current_regs = regs;
 
           /* Deliver the IRQ */
 
           irq_dispatch(irq, regs);
 
-          /* Indicate that we are no longer in an interrupt handler */
+          /* Restore the previous value of current_regs.  NULL would indicate that
+           * we are no longer in an interrupt handler.  It will be non-NULL if we
+           * are returning from a nested interrupt.
+           */
 
-          current_regs = NULL;
+          current_regs = savestate;
 
           /* Unmask the last interrupt (global interrupts are still
            * disabled).
diff --git a/nuttx/arch/arm/src/lpc313x/lpc313x_irq.c b/nuttx/arch/arm/src/lpc313x/lpc313x_irq.c
index 35ef3e89e..9b7f10e12 100755
--- a/nuttx/arch/arm/src/lpc313x/lpc313x_irq.c
+++ b/nuttx/arch/arm/src/lpc313x/lpc313x_irq.c
@@ -2,7 +2,7 @@
  * arch/arm/src/lpc313x/lpc313x_irq.c
  * arch/arm/src/chip/lpc313x_irq.c
  *
- *   Copyright (C) 2009-2010 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2009-2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -64,7 +64,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/sam3u/sam3u_irq.c b/nuttx/arch/arm/src/sam3u/sam3u_irq.c
index 1d19c126e..228be0f1f 100755
--- a/nuttx/arch/arm/src/sam3u/sam3u_irq.c
+++ b/nuttx/arch/arm/src/sam3u/sam3u_irq.c
@@ -75,7 +75,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/stm32/stm32_irq.c b/nuttx/arch/arm/src/stm32/stm32_irq.c
index 7f963a117..b27f5448e 100644
--- a/nuttx/arch/arm/src/stm32/stm32_irq.c
+++ b/nuttx/arch/arm/src/stm32/stm32_irq.c
@@ -75,7 +75,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/arm/src/str71x/str71x_decodeirq.c b/nuttx/arch/arm/src/str71x/str71x_decodeirq.c
index 4182ab417..8a24ea44d 100644
--- a/nuttx/arch/arm/src/str71x/str71x_decodeirq.c
+++ b/nuttx/arch/arm/src/str71x/str71x_decodeirq.c
@@ -1,7 +1,7 @@
 /********************************************************************************
  * arch/arm/src/str71x/str71x_decodeirq.c
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -108,11 +108,13 @@ void up_decodeirq(uint32_t *regs)
 
   if (irq < NR_IRQS)
     {
+      uint32_t* savestate;
+
       /* Current regs non-zero indicates that we are processing an interrupt;
        * current_regs is also used to manage interrupt level context switches.
        */
 
-      DEBUGASSERT(current_regs == NULL);
+      savestate     = (uint32_t*)current_regs;
       current_regs = regs;
 
       /* Mask and acknowledge the interrupt */
@@ -123,9 +125,12 @@ void up_decodeirq(uint32_t *regs)
 
       irq_dispatch(irq, regs);
 
-      /* Indicate that we are no long in an interrupt handler */
+      /* Restore the previous value of current_regs.  NULL would indicate that
+       * we are no longer in an interrupt handler.  It will be non-NULL if we
+       * are returning from a nested interrupt.
+       */
 
-      current_regs = NULL;
+      current_regs = savestate;
 
       /* Unmask the last interrupt (global interrupts are still disabled) */
 
diff --git a/nuttx/arch/arm/src/str71x/str71x_irq.c b/nuttx/arch/arm/src/str71x/str71x_irq.c
index d27412e17..c5c359cdf 100644
--- a/nuttx/arch/arm/src/str71x/str71x_irq.c
+++ b/nuttx/arch/arm/src/str71x/str71x_irq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/arm/src/st71x/st71x_irq.c
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -58,7 +58,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/avr/src/at32uc3/at32uc3_irq.c b/nuttx/arch/avr/src/at32uc3/at32uc3_irq.c
index 1cdc7ed7d..ce42fd03d 100644
--- a/nuttx/arch/avr/src/at32uc3/at32uc3_irq.c
+++ b/nuttx/arch/avr/src/at32uc3/at32uc3_irq.c
@@ -2,7 +2,7 @@
  * arch/avr/src/at32uc3_/at32uc3_irq.c
  * arch/avr/src/chip/at32uc3_irq.c
  *
- *   Copyright (C) 2010 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2010-2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -83,7 +83,7 @@ extern uint32_t avr32_int3;
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Types
diff --git a/nuttx/arch/avr/src/avr32/up_doirq.c b/nuttx/arch/avr/src/avr32/up_doirq.c
index abc0cf54d..061583393 100644
--- a/nuttx/arch/avr/src/avr32/up_doirq.c
+++ b/nuttx/arch/avr/src/avr32/up_doirq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/avr/src/avr32/up_doirq.c
  *
- *   Copyright (C) 2010 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2010-2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -76,6 +76,8 @@ uint32_t *up_doirq(int irq, uint32_t *regs)
 #ifdef CONFIG_SUPPRESS_INTERRUPTS
   PANIC(OSERR_ERREXCEPTION);
 #else
+  uint32_t *savestate;
+
   /* Nested interrupts are not supported in this implementation.  If you want
    * implemented nested interrupts, you would have to (1) change the way that
    * current regs is handled and (2) the design associated with
@@ -86,7 +88,7 @@ uint32_t *up_doirq(int irq, uint32_t *regs)
    * current_regs is also used to manage interrupt level context switches.
    */
 
-  DEBUGASSERT(current_regs == NULL);
+  savestate    = (uint32_t*)current_regs;
   current_regs = regs;
 
   /* Deliver the IRQ */
@@ -101,9 +103,12 @@ uint32_t *up_doirq(int irq, uint32_t *regs)
 
   regs = current_regs;
 
-  /* Indicate that we are no long in an interrupt handler */
+  /* Restore the previous value of current_regs.  NULL would indicate that
+   * we are no longer in an interrupt handler.  It will be non-NULL if we
+   * are returning from a nested interrupt.
+   */
 
-  current_regs = NULL;
+  current_regs = savestate;
 #endif
   up_ledoff(LED_INIRQ);
   return regs;
diff --git a/nuttx/arch/avr/src/common/up_internal.h b/nuttx/arch/avr/src/common/up_internal.h
index ad5fc30f3..413e44078 100644
--- a/nuttx/arch/avr/src/common/up_internal.h
+++ b/nuttx/arch/avr/src/common/up_internal.h
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/avr/src/common/up_internal.h
  *
- *   Copyright (C) 2010 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2010-2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -70,7 +70,7 @@
  * state from the TCB.
  */
 
-#define up_savestate(regs)    up_copystate(regs, current_regs)
+#define up_savestate(regs)    up_copystate(regs, (uint32_t*)current_regs)
 #define up_restorestate(regs) (current_regs = regs)
 
 /****************************************************************************
@@ -91,7 +91,7 @@ typedef void (*up_vector_t)(void);
  * interrupt processing.
  */
 
-extern uint32_t *current_regs;
+extern volatile uint32_t *current_regs;
 
 /* This is the beginning of heap as provided from up_head.S.
  * This is the first address in DRAM after the loaded
diff --git a/nuttx/arch/hc/src/common/up_doirq.c b/nuttx/arch/hc/src/common/up_doirq.c
index 05dbaa2cf..adb3f81ce 100644
--- a/nuttx/arch/hc/src/common/up_doirq.c
+++ b/nuttx/arch/hc/src/common/up_doirq.c
@@ -76,6 +76,8 @@ uint8_t *up_doirq(int irq, uint8_t *regs)
 #ifdef CONFIG_SUPPRESS_INTERRUPTS
   PANIC(OSERR_ERREXCEPTION);
 #else
+  uint8_t *savestate;
+
   /* Nested interrupts are not supported in this implementation.  If you want
    * implemented nested interrupts, you would have to (1) change the way that
    * current regs is handled and (2) the design associated with
@@ -86,7 +88,7 @@ uint8_t *up_doirq(int irq, uint8_t *regs)
    * current_regs is also used to manage interrupt level context switches.
    */
 
-  DEBUGASSERT(current_regs == NULL);
+  savestate    = (uint8_t*)current_regs;
   current_regs = regs;
 
   /* Deliver the IRQ */
@@ -101,9 +103,12 @@ uint8_t *up_doirq(int irq, uint8_t *regs)
 
   regs = current_regs;
 
-  /* Indicate that we are no long in an interrupt handler */
+  /* Restore the previous value of current_regs.  NULL would indicate that
+   * we are no longer in an interrupt handler.  It will be non-NULL if we
+   * are returning from a nested interrupt.
+   */
 
-  current_regs = NULL;
+  current_regs = savestate;
 #endif
   up_ledoff(LED_INIRQ);
   return regs;
diff --git a/nuttx/arch/hc/src/common/up_internal.h b/nuttx/arch/hc/src/common/up_internal.h
index 8879eee57..1a30f28e5 100755
--- a/nuttx/arch/hc/src/common/up_internal.h
+++ b/nuttx/arch/hc/src/common/up_internal.h
@@ -81,7 +81,7 @@
  * a referenced is passed to get the state from the TCB.
  */
 
-#define up_savestate(regs)    up_copystate(regs, current_regs)
+#define up_savestate(regs)    up_copystate(regs, (uint8_t*)current_regs)
 #define up_restorestate(regs) (current_regs = regs)
 
 /****************************************************************************
diff --git a/nuttx/arch/hc/src/m9s12/m9s12_irq.c b/nuttx/arch/hc/src/m9s12/m9s12_irq.c
index 1e95c4e68..ab4758925 100755
--- a/nuttx/arch/hc/src/m9s12/m9s12_irq.c
+++ b/nuttx/arch/hc/src/m9s12/m9s12_irq.c
@@ -60,7 +60,7 @@
  * Public Data
  ****************************************************************************/
 
-uint8_t *current_regs;
+volatile uint8_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/sh/src/common/up_doirq.c b/nuttx/arch/sh/src/common/up_doirq.c
index 6e64a623c..0ec82b7d9 100644
--- a/nuttx/arch/sh/src/common/up_doirq.c
+++ b/nuttx/arch/sh/src/common/up_doirq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/sh/src/common/up_doirq.c
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -77,11 +77,14 @@ uint32_t *up_doirq(int irq, uint32_t* regs)
 #else
   if ((unsigned)irq < NR_IRQS)
     {
+       uint32_t *savestate;
+
        /* Current regs non-zero indicates that we are processing
         * an interrupt; current_regs is also used to manage
         * interrupt level context switches.
         */
 
+       savestate    = (uint32_t*)current_regs;
        current_regs = regs;
 
        /* Mask and acknowledge the interrupt (if supported by the chip) */
@@ -100,9 +103,12 @@ uint32_t *up_doirq(int irq, uint32_t* regs)
 
        regs = current_regs;
 
-       /* Indicate that we are no longer in an interrupt handler */
+       /* Restore the previous value of current_regs.  NULL would indicate that
+        * we are no longer in an interrupt handler.  It will be non-NULL if we
+        * are returning from a nested interrupt.
+        */
 
-       current_regs = NULL;
+       current_regs = savestate;
 
        /* Unmask the last interrupt (global interrupts are still
         * disabled.
diff --git a/nuttx/arch/sh/src/common/up_internal.h b/nuttx/arch/sh/src/common/up_internal.h
index 7840caf66..7b1fb5f33 100644
--- a/nuttx/arch/sh/src/common/up_internal.h
+++ b/nuttx/arch/sh/src/common/up_internal.h
@@ -98,7 +98,7 @@ typedef void (*up_vector_t)(void);
  * interrupt processing.
  */
 
-extern uint32_t *current_regs;
+extern volatile uint32_t *current_regs;
 
 /* This is the beginning of heap as provided from up_head.S.
  * This is the first address in DRAM after the loaded
diff --git a/nuttx/arch/sh/src/common/up_reprioritizertr.c b/nuttx/arch/sh/src/common/up_reprioritizertr.c
index cc9d0ff47..58a142563 100644
--- a/nuttx/arch/sh/src/common/up_reprioritizertr.c
+++ b/nuttx/arch/sh/src/common/up_reprioritizertr.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  *  arch/sh/src/common/up_reprioritizertr.c
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/nuttx/arch/sh/src/m16c/m16c_irq.c b/nuttx/arch/sh/src/m16c/m16c_irq.c
index 10e129412..5cfb43e8d 100644
--- a/nuttx/arch/sh/src/m16c/m16c_irq.c
+++ b/nuttx/arch/sh/src/m16c/m16c_irq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/sh/src/m16c/m16c_irq.c
  *
- *   Copyright (C) 2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -57,7 +57,7 @@
  * structure.  If is non-NULL only during interrupt processing.
  */
 
-uint32_t *current_regs; /* Actually a pointer to the beginning of a uint8_t array */
+volatile uint32_t *current_regs; /* Actually a pointer to the beginning of a uint8_t array */
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/sh/src/sh1/sh1_dumpstate.c b/nuttx/arch/sh/src/sh1/sh1_dumpstate.c
index cf6a16cbe..ddfa5e455 100755
--- a/nuttx/arch/sh/src/sh1/sh1_dumpstate.c
+++ b/nuttx/arch/sh/src/sh1/sh1_dumpstate.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/sh/src/sh1/sh1_assert.c
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -113,7 +113,7 @@ static void sh1_stackdump(uint32_t sp, uint32_t stack_base)
 
 static inline void sh1_registerdump(void)
 {
-  uint32_t *ptr = current_regs;
+  uint32_t *ptr = (uint32_t*)current_regs;
 
   /* Are user registers available from interrupt processing? */
 
diff --git a/nuttx/arch/sh/src/sh1/sh1_irq.c b/nuttx/arch/sh/src/sh1/sh1_irq.c
index c5b33cc3e..d76d1d94c 100644
--- a/nuttx/arch/sh/src/sh1/sh1_irq.c
+++ b/nuttx/arch/sh/src/sh1/sh1_irq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/sh/src/sh1/sh1_irq.c
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -57,7 +57,7 @@
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/x86/src/common/up_assert.c b/nuttx/arch/x86/src/common/up_assert.c
index 55ba376b4..776784656 100644
--- a/nuttx/arch/x86/src/common/up_assert.c
+++ b/nuttx/arch/x86/src/common/up_assert.c
@@ -198,7 +198,7 @@ static void up_dumpstate(void)
 
   if (current_regs != NULL)
     {
-      up_registerdump(current_regs);
+      up_registerdump((uint32_t*)current_regs);
 	}
 }
 #else
diff --git a/nuttx/arch/x86/src/common/up_internal.h b/nuttx/arch/x86/src/common/up_internal.h
index 51f79beb3..185d0afc0 100644
--- a/nuttx/arch/x86/src/common/up_internal.h
+++ b/nuttx/arch/x86/src/common/up_internal.h
@@ -99,7 +99,7 @@ typedef void (*up_vector_t)(void);
  * structure.  If is non-NULL only during interrupt processing.
  */
 
-extern uint32_t *current_regs;
+extern volatile uint32_t *current_regs;
 
 /* This is the beginning of heap as provided from up_head.S. This is the first
  * address in DRAM after the loaded program+bss+idle stack.  The end of the
diff --git a/nuttx/arch/x86/src/i486/up_irq.c b/nuttx/arch/x86/src/i486/up_irq.c
index 627c727de..01da4962e 100755
--- a/nuttx/arch/x86/src/i486/up_irq.c
+++ b/nuttx/arch/x86/src/i486/up_irq.c
@@ -72,7 +72,7 @@ static inline void up_idtinit(void);
  * Public Data
  ****************************************************************************/
 
-uint32_t *current_regs;
+volatile uint32_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/x86/src/i486/up_savestate.c b/nuttx/arch/x86/src/i486/up_savestate.c
index d5f97fa85..1d35c62a9 100644
--- a/nuttx/arch/x86/src/i486/up_savestate.c
+++ b/nuttx/arch/x86/src/i486/up_savestate.c
@@ -80,7 +80,7 @@ void up_savestate(uint32_t *regs)
   
   /* First, just copy all of the registers */
 
-  up_copystate(regs, current_regs);
+  up_copystate(regs, (uint32_t*)current_regs);
 
   /* The RES_SP and REG_SS values will not be saved by the interrupt handling
    * logic if there is no change in privilege level.  In that case, we will
diff --git a/nuttx/arch/x86/src/qemu/qemu_handlers.c b/nuttx/arch/x86/src/qemu/qemu_handlers.c
index fbcb327aa..a85370f76 100644
--- a/nuttx/arch/x86/src/qemu/qemu_handlers.c
+++ b/nuttx/arch/x86/src/qemu/qemu_handlers.c
@@ -86,6 +86,8 @@ static void idt_outb(uint8_t val, uint16_t addr)
 #ifndef CONFIG_SUPPRESS_INTERRUPTS
 static uint32_t *common_handler(int irq, uint32_t *regs)
 {
+  uint32_t *savestate;
+
   up_ledon(LED_INIRQ);
 
   /* Nested interrupts are not supported in this implementation.  If you want
@@ -98,7 +100,7 @@ static uint32_t *common_handler(int irq, uint32_t *regs)
    * current_regs is also used to manage interrupt level context switches.
    */
 
-  DEBUGASSERT(current_regs == NULL);
+  savestate    = (uint32_t*)current_regs;
   current_regs = regs;
 
   /* Deliver the IRQ */
@@ -111,11 +113,14 @@ static uint32_t *common_handler(int irq, uint32_t *regs)
    * switch occurred during interrupt processing.
    */
 
-  regs = current_regs;
+  regs = (uint32_t*)current_regs;
 
-  /* Indicate that we are no long in an interrupt handler */
+  /* Restore the previous value of current_regs.  NULL would indicate that
+   * we are no longer in an interrupt handler.  It will be non-NULL if we
+   * are returning from a nested interrupt.
+   */
 
-  current_regs = NULL;
+  current_regs = savestate;
   return regs;
 }
 #endif
diff --git a/nuttx/arch/z16/src/common/up_doirq.c b/nuttx/arch/z16/src/common/up_doirq.c
index e7e43b24d..3adddf6db 100644
--- a/nuttx/arch/z16/src/common/up_doirq.c
+++ b/nuttx/arch/z16/src/common/up_doirq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * common/up_doirq.c
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -88,31 +88,37 @@ FAR chipreg_t *up_doirq(int irq, FAR chipreg_t *regs)
 #else
   if ((unsigned)irq < NR_IRQS)
     {
-       /* Current regs non-zero indicates that we are processing
-        * an interrupt; current_regs is also used to manage
-        * interrupt level context switches.
-        */
+      FAR chipreg_t *savestate;
 
-       current_regs = regs;
+      /* Current regs non-zero indicates that we are processing
+       * an interrupt; current_regs is also used to manage
+       * interrupt level context switches.
+       */
 
-       /* Mask and acknowledge the interrupt */
+      savestate    = (uint32_t*)current_regs;
+      current_regs = regs;
 
-       up_maskack_irq(irq);
+      /* Mask and acknowledge the interrupt */
 
-       /* Deliver the IRQ */
+      up_maskack_irq(irq);
 
-       irq_dispatch(irq, regs);
+      /* Deliver the IRQ */
 
-       /* Indicate that we are no long in an interrupt handler */
+      irq_dispatch(irq, regs);
 
-       ret          = current_regs;
-       current_regs = NULL;
+      /* Restore the previous value of current_regs.  NULL would indicate that
+       * we are no longer in an interrupt handler.  It will be non-NULL if we
+       * are returning from a nested interrupt.
+       */
 
-       /* Unmask the last interrupt (global interrupts are still
-        * disabled.
-        */
+      ret          = current_regs;
+      current_regs = savestate;
 
-       up_enable_irq(irq);
+      /* Unmask the last interrupt (global interrupts are still
+       * disabled.
+       */
+
+      up_enable_irq(irq);
     }
   up_ledoff(LED_INIRQ);
 #endif
diff --git a/nuttx/arch/z16/src/common/up_initialize.c b/nuttx/arch/z16/src/common/up_initialize.c
index 2121f73d9..063ccdf71 100644
--- a/nuttx/arch/z16/src/common/up_initialize.c
+++ b/nuttx/arch/z16/src/common/up_initialize.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * common/up_initialize.c
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -68,7 +68,7 @@
  * interrupt processing.
  */
 
-FAR chipreg_t *current_regs;
+volatile FAR chipreg_t *current_regs;
 
 /****************************************************************************
  * Private Types
diff --git a/nuttx/arch/z16/src/common/up_internal.h b/nuttx/arch/z16/src/common/up_internal.h
index fa527fd62..117d7f405 100644
--- a/nuttx/arch/z16/src/common/up_internal.h
+++ b/nuttx/arch/z16/src/common/up_internal.h
@@ -1,7 +1,7 @@
 /****************************************************************************
  * common/up_internal.h
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -74,7 +74,7 @@
 /* Macros for portability */
 
 #define IN_INTERRUPT             (current_regs != NULL)
-#define SAVE_IRQCONTEXT(tcb)     up_copystate((tcb)->xcp.regs, current_regs)
+#define SAVE_IRQCONTEXT(tcb)     up_copystate((tcb)->xcp.regs, (FAR chipreg_t*)current_regs)
 #define SET_IRQCONTEXT(tcb)      do { current_regs = (tcb)->xcp.regs; } while (0)
 #define SAVE_USERCONTEXT(tcb)    up_saveusercontext((tcb)->xcp.regs)
 #define RESTORE_USERCONTEXT(tcb) up_restoreusercontext((tcb)->xcp.regs)
@@ -98,7 +98,7 @@ typedef void (*up_vector_t)(void);
  * interrupt processing.
  */
 
-extern FAR chipreg_t *current_regs;
+extern voltile FAR chipreg_t *current_regs;
 #endif
 
 /****************************************************************************
diff --git a/nuttx/arch/z80/src/common/up_doirq.c b/nuttx/arch/z80/src/common/up_doirq.c
index 2c4c9e113..828806a49 100644
--- a/nuttx/arch/z80/src/common/up_doirq.c
+++ b/nuttx/arch/z80/src/common/up_doirq.c
@@ -84,6 +84,8 @@ FAR chipreg_t *up_doirq(uint8_t irq, FAR chipreg_t *regs)
 #else
   if (irq < NR_IRQS)
     {
+       FAR chipreg_t *savestate;
+
        /* Indicate that we have entered IRQ processing logic */
 
        IRQ_ENTER(irq, regs);
diff --git a/nuttx/arch/z80/src/ez80/ez80_irq.c b/nuttx/arch/z80/src/ez80/ez80_irq.c
index 38a51c9c4..d89bff859 100644
--- a/nuttx/arch/z80/src/ez80/ez80_irq.c
+++ b/nuttx/arch/z80/src/ez80/ez80_irq.c
@@ -57,7 +57,7 @@
  * structure.  If is non-NULL only during interrupt processing.
  */
 
-chipreg_t *current_regs;
+volatile chipreg_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/arch/z80/src/ez80/switch.h b/nuttx/arch/z80/src/ez80/switch.h
index b1d71669b..3b7f1bd95 100644
--- a/nuttx/arch/z80/src/ez80/switch.h
+++ b/nuttx/arch/z80/src/ez80/switch.h
@@ -2,7 +2,7 @@
  * arch/z80/src/ez80/switch.h
  * arch/z80/src/chip/switch.h
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -61,7 +61,7 @@
 
 #define INIT_IRQCONTEXT()        current_regs = NULL
 
-/* IN_INTERRUPT returns true if the system is current operating in the interrupt
+/* IN_INTERRUPT returns true if the system is currently operating in the interrupt
  * context.  IN_INTERRUPT is the inline equivalent of up_interrupt_context().
  */
 
@@ -69,11 +69,15 @@
 
 /* The following macro is used when the system enters interrupt handling logic */
 
-#define IRQ_ENTER(irq, regs)     current_regs = (regs)
+#define IRQ_ENTER(irq, regs) \
+  do { \
+    savestate    = (FAR chipreg_t *)current_regs; \
+    current_regs = (regs); \
+  } while (0)
 
 /* The following macro is used when the system exits interrupt handling logic */
 
-#define IRQ_LEAVE(irq)           current_regs = NULL
+#define IRQ_LEAVE(irq)           current_regs = savestate
 
 /* The following macro is used to sample the interrupt state (as a opaque handle) */
 
@@ -81,11 +85,11 @@
 
 /* Save the current IRQ context in the specified TCB */
 
-#define SAVE_IRQCONTEXT(tcb)     ez80_copystate((tcb)->xcp.regs, current_regs)
+#define SAVE_IRQCONTEXT(tcb)     ez80_copystate((tcb)->xcp.regs, (FAR chipreg_t*)current_regs)
 
 /* Set the current IRQ context to the state specified in the TCB */
 
-#define SET_IRQCONTEXT(tcb)      ez80_copystate(current_regs, (tcb)->xcp.regs)
+#define SET_IRQCONTEXT(tcb)      ez80_copystate((FAR chipreg_t*)current_regs, (tcb)->xcp.regs)
 
 /* Save the user context in the specified TCB.  User context saves can be simpler
  * because only those registers normally saved in a C called need be stored.
@@ -116,7 +120,7 @@
  * If is non-NULL only during interrupt processing.
  */
 
-extern chipreg_t *current_regs;
+extern volatile chipreg_t *current_regs;
 #endif
 
 /************************************************************************************
@@ -133,19 +137,19 @@ extern "C" {
 
 /* Defined in ez80_copystate.c */
 
-EXTERN void ez80_copystate(chipreg_t *dest, const chipreg_t *src);
+EXTERN void ez80_copystate(FAR chipreg_t *dest, FAR const chipreg_t *src);
 
 /* Defined in ez80_saveusercontext.asm */
 
-EXTERN int ez80_saveusercontext(chipreg_t *regs);
+EXTERN int ez80_saveusercontext(FAR chipreg_t *regs);
 
 /* Defined in ez80_restorecontext.asm */
 
-EXTERN void ez80_restorecontext(chipreg_t *regs);
+EXTERN void ez80_restorecontext(FAR chipreg_t *regs);
 
 /* Defined in ez80_sigsetup.c */
 
-EXTERN void ez80_sigsetup(_TCB *tcb, sig_deliver_t sigdeliver, chipreg_t *regs);
+EXTERN void ez80_sigsetup(FAR _TCB *tcb, sig_deliver_t sigdeliver, chipreg_t *regs);
 
 /* Defined in ez80_registerdump.c */
 
diff --git a/nuttx/arch/z80/src/z8/switch.h b/nuttx/arch/z80/src/z8/switch.h
index 69e766cf6..c37d7bcd0 100644
--- a/nuttx/arch/z80/src/z8/switch.h
+++ b/nuttx/arch/z80/src/z8/switch.h
@@ -2,7 +2,7 @@
  * arch/z80/src/z8/switch.h
  * arch/z80/src/chip/switch.h
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -105,7 +105,7 @@
     g_z8irqstate.state = Z8_IRQSTATE_NONE; \
   } while (0)
 
-/* IN_INTERRUPT returns true if the system is current operating in the interrupt
+/* IN_INTERRUPT returns true if the system is currently operating in the interrupt
  * context.  IN_INTERRUPT is the inline equivalent of up_interrupt_context().
  */
 
@@ -114,8 +114,15 @@
 
 /* The following macro is used when the system enters interrupt handling logic */
 
+#define IRQ_SAVE(irq, regs)      savestate    = (FAR chipreg_t *)current_regs;
+#define IRQ_ENTER(irq, regs)     current_regs = (regs)
+
+/* The following macro is used when the system exits interrupt handling logic */
+
 #define IRQ_ENTER(irq, regs) \
   do { \
+    savestate.state    = g_z8irqstate.state; \
+    savestate.regs     = g_z8irqstate.regs; \
     g_z8irqstate.state = Z8_IRQSTATE_ENTRY; \
     g_z8irqstate.regs  = (regs); \
     up_maskack_irq(irq); \
@@ -125,7 +132,8 @@
 
 #define IRQ_LEAVE(irq) \
   do { \
-    g_z8irqstate.state = Z8_IRQSTATE_NONE; \
+    g_z8irqstate.state = savestate.state; \
+    g_z8irqstate.regs  = savestate.regs; \
     up_enable_irq(irq); \
   } while (0)
 
diff --git a/nuttx/arch/z80/src/z80/switch.h b/nuttx/arch/z80/src/z80/switch.h
index f30f41b9c..1b54ada5e 100644
--- a/nuttx/arch/z80/src/z80/switch.h
+++ b/nuttx/arch/z80/src/z80/switch.h
@@ -2,7 +2,7 @@
  * arch/z80/src/z80/switch.h
  * arch/z80/src/chip/switch.h
  *
- *   Copyright (C) 2008-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -68,11 +68,15 @@
 
 /* The following macro is used when the system enters interrupt handling logic */
 
-#define IRQ_ENTER(irq, regs)     current_regs = (regs)
+#define IRQ_ENTER(irq, regs) \
+  do { \
+    savestate    = (FAR chipreg_t *)current_regs; \
+    current_regs = (regs); \
+  } while (0)
 
 /* The following macro is used when the system exits interrupt handling logic */
 
-#define IRQ_LEAVE(irq)           current_regs = NULL
+#define IRQ_LEAVE(irq)           current_regs = savestate
 
 /* The following macro is used to sample the interrupt state (as a opaque handle) */
 
@@ -80,11 +84,11 @@
 
 /* Save the current IRQ context in the specified TCB */
 
-#define SAVE_IRQCONTEXT(tcb)     z80_copystate((tcb)->xcp.regs, current_regs)
+#define SAVE_IRQCONTEXT(tcb)     z80_copystate((tcb)->xcp.regs, (FAR chipreg_t*)current_regs)
 
 /* Set the current IRQ context to the state specified in the TCB */
 
-#define SET_IRQCONTEXT(tcb)      z80_copystate(current_regs, (tcb)->xcp.regs)
+#define SET_IRQCONTEXT(tcb)      z80_copystate((FAR chipreg_t*)current_regs, (tcb)->xcp.regs)
 
 /* Save the user context in the specified TCB.  User context saves can be simpler
  * because only those registers normally saved in a C called need be stored.
@@ -103,16 +107,19 @@
 #define _REGISTER_DUMP()         z80_registerdump()
 
 /************************************************************************************
+ * Public Types
+ ************************************************************************************/
+
+/************************************************************************************
  * Public Variables
  ************************************************************************************/
 
 #ifndef __ASSEMBLY__
-/* This holds a references to the current interrupt level
- * register storage structure.  If is non-NULL only during
- * interrupt processing.
+/* This holds a references to the current interrupt level register storage structure.
+ * If is non-NULL only during interrupt processing.
  */
 
-extern chipreg_t *current_regs;
+extern volatile chipreg_t *current_regs;
 #endif
 
 /************************************************************************************
diff --git a/nuttx/arch/z80/src/z80/z80_irq.c b/nuttx/arch/z80/src/z80/z80_irq.c
index 8b46acc40..5efd36b9f 100644
--- a/nuttx/arch/z80/src/z80/z80_irq.c
+++ b/nuttx/arch/z80/src/z80/z80_irq.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * arch/z80/src/z80/z80_irq.c
  *
- *   Copyright (C) 2007-2009 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -56,7 +56,7 @@
  * structure.  If is non-NULL only during interrupt processing.
  */
 
-chipreg_t *current_regs;
+volatile chipreg_t *current_regs;
 
 /****************************************************************************
  * Private Data
diff --git a/nuttx/configs/ntosd-dm320/thttpd/appconfig b/nuttx/configs/ntosd-dm320/thttpd/appconfig
index 1a0b0718e..42bcab4d4 100644
--- a/nuttx/configs/ntosd-dm320/thttpd/appconfig
+++ b/nuttx/configs/ntosd-dm320/thttpd/appconfig
@@ -37,8 +37,8 @@
 
 CONFIGURED_APPS += examples/thttpd
 
-
 # Networking support
 
 CONFIGURED_APPS += netutils/uiplib
 CONFIGURED_APPS += netutils/thttpd
+