x86: Move address environment switch from the task switchers to the interrupt handler. That may save doing the action multiple times per interrupt

arch/x86/src/common/up_blocktask.c

@@ -136,19 +136,11 @@ void up_block_task(struct tcb_s *tcb, tstate_t task_state)
 
           rtcb = (struct tcb_s*)g_readytorun.head;
 
-          /* Then switch contexts */
+          /* Then switch contexts.  Any necessary address environment
+           * changes will be made when the interrupt returns.
+           */
 
           up_restorestate(rtcb->xcp.regs);
-
-#ifdef CONFIG_ARCH_ADDRENV
-         /* Make sure that the address environment for the previously
-          * running task is closed down gracefully (data caches dump,
-          * MMU flushed) and set up the address environment for the new
-          * thread at the head of the ready-to-run list.
-          */
-
-         (void)group_addrenv(rtcb);
-#endif
         }
 
       /* Copy the user C context into the TCB at the (old) head of the

arch/x86/src/common/up_unblocktask.c

@@ -126,19 +126,11 @@ void up_unblock_task(struct tcb_s *tcb)
 
           rtcb = (struct tcb_s*)g_readytorun.head;
 
-          /* Then switch contexts */
+          /* Then switch contexts.  Any necessary address environment
+           * changes will be made when the interrupt returns.
+           */
 
           up_restorestate(rtcb->xcp.regs);
-
-#ifdef CONFIG_ARCH_ADDRENV
-         /* Make sure that the address environment for the previously
-          * running task is closed down gracefully (data caches dump,
-          * MMU flushed) and set up the address environment for the new
-          * thread at the head of the ready-to-run list.
-          */
-
-         (void)group_addrenv(rtcb);
-#endif
         }
 
       /* We are not in an interrupt handler.  Copy the user C context

arch/x86/src/qemu/qemu_handlers.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  *  arch/x86/src/qemu/qemu_handlers.c
  *
- *   Copyright (C) 2011-2012 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2011-2012,2014 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -87,27 +87,49 @@ 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;
-
   board_led_on(LED_INIRQ);
 
-  /* 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
-   * CONFIG_ARCH_INTERRUPTSTACK.
-   */
-
   /* Current regs non-zero indicates that we are processing an interrupt;
    * current_regs is also used to manage interrupt level context switches.
+   *
+   * Nested interrupts are not supported.
    */
 
-  savestate    = (uint32_t*)current_regs;
+  DEBUGASSERT(current_regs == NULL);
   current_regs = regs;
 
   /* Deliver the IRQ */
 
   irq_dispatch(irq, regs);
 
+#if defined(CONFIG_ARCH_FPU) || defined(CONFIG_ARCH_ADDRENV)
+  /* Check for a context switch.  If a context switch occurred, then
+   * current_regs will have a different value than it did on entry.  If an
+   * interrupt level context switch has occurred, then restore the floating
+   * point state and the establish the correct address environment before
+   * returning from the interrupt.
+   */
+
+  if (regs != current_regs)
+    {
+#ifdef CONFIG_ARCH_FPU
+      /* Restore floating point registers */
+
+      up_restorefpu((uint32_t*)current_regs);
+#endif
+
+#ifdef CONFIG_ARCH_ADDRENV
+      /* Make sure that the address environment for the previously
+       * running task is closed down gracefully (data caches dump,
+       * MMU flushed) and set up the address environment for the new
+       * thread at the head of the ready-to-run list.
+       */
+
+      (void)group_addrenv(rtcb);
+#endif
+    }
+#endif
+
   /* If a context switch occurred while processing the interrupt then
    * current_regs may have change value.  If we return any value different
    * from the input regs, then the lower level will know that a context
@@ -116,12 +138,11 @@ static uint32_t *common_handler(int irq, uint32_t *regs)
 
   regs = (uint32_t*)current_regs;
 
-  /* Restore the previous value of current_regs.  NULL would indicate that
+  /* Set current_regs to NULL to indicate that we are no longer in an
-   * we are no longer in an interrupt handler.  It will be non-NULL if we
+   * interrupt handler.
-   * are returning from a nested interrupt.
    */
 
-  current_regs = savestate;
+  current_regs = NULL;
   return regs;
 }
 #endif