diff --git a/arch/arm/src/common/arm_createstack.c b/arch/arm/src/common/arm_createstack.c
index ac5d63787e..025aa5844f 100644
--- a/arch/arm/src/common/arm_createstack.c
+++ b/arch/arm/src/common/arm_createstack.c
@@ -84,8 +84,6 @@
 
 int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
 {
-  stack_size = STACK_ALIGN_UP(stack_size);
-
 #ifdef CONFIG_TLS_ALIGNED
   /* The allocated stack size must not exceed the maximum possible for the
    * TLS feature.
@@ -138,14 +136,14 @@ int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
 
       if (ttype == TCB_FLAG_TTYPE_KERNEL)
         {
-          tcb->stack_alloc_ptr = kmm_memalign(STACK_ALIGNMENT, stack_size);
+          tcb->stack_alloc_ptr = kmm_malloc(stack_size);
         }
       else
 #endif
         {
           /* Use the user-space allocator if this is a task or pthread */
 
-          tcb->stack_alloc_ptr = kumm_memalign(STACK_ALIGNMENT, stack_size);
+          tcb->stack_alloc_ptr = kumm_malloc(stack_size);
         }
 #endif /* CONFIG_TLS_ALIGNED */
 
@@ -163,6 +161,9 @@ int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
 
   if (tcb->stack_alloc_ptr)
     {
+      uintptr_t top_of_stack;
+      size_t size_of_stack;
+
       /* The ARM uses a "full descending" stack:
        * the stack grows toward lower addresses in memory.
        * The stack pointer register points to the last pushed item in
@@ -170,14 +171,17 @@ int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
        * Items on the stack are referenced as positive word offsets from sp.
        */
 
-      /* Since both stack_alloc_ptr and stack_size are in
-       * STACK_ALIGNMENT, and the stack ptr is decremented before
-       * the first write, we can directly save our variables to struct
-       * tcb_s.
-       */
+      top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
+
+      /* Align the top of stack to STACK_ALIGNMENT. */
+
+      top_of_stack  = STACK_ALIGN_DOWN(top_of_stack);
+      size_of_stack = top_of_stack - (uintptr_t)tcb->stack_alloc_ptr;
+
+      /* Save the adjusted stack values in the struct tcb_s */
 
-      tcb->adj_stack_size = stack_size;
       tcb->stack_base_ptr = tcb->stack_alloc_ptr;
+      tcb->adj_stack_size = size_of_stack;
 
 #ifdef CONFIG_STACK_COLORATION
       /* If stack debug is enabled, then fill the stack with a
diff --git a/arch/ceva/src/common/up_createstack.c b/arch/ceva/src/common/up_createstack.c
index f9e75137d4..0868af0778 100644
--- a/arch/ceva/src/common/up_createstack.c
+++ b/arch/ceva/src/common/up_createstack.c
@@ -179,7 +179,7 @@ int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
 
   if (tcb->stack_alloc_ptr)
     {
-      FAR void *top_of_stack;
+      uintptr_t top_of_stack;
       size_t size_of_stack;
 
       /* The CEVA uses a push-down stack:  the stack grows toward lower
@@ -193,12 +193,13 @@ int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
        * boundary
        */
 
-      size_of_stack = STACK_ALIGN_DOWN(stack_size);
-      top_of_stack  = tcb->stack_alloc_ptr + size_of_stack;
+      top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
+      top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
+      size_of_stack = top_of_stack - (uintptr_t)tcb->stack_alloc_ptr;
 
       /* Save the adjusted stack values in the struct tcb_s */
 
-      tcb->stack_base_ptr = top_of_stack;
+      tcb->stack_base_ptr = tcb->stack_alloc_ptr;
       tcb->adj_stack_size = size_of_stack;
 
 #ifdef CONFIG_STACK_COLORATION
diff --git a/arch/ceva/src/common/up_stackframe.c b/arch/ceva/src/common/up_stackframe.c
index 12ce130af4..9c142b4711 100644
--- a/arch/ceva/src/common/up_stackframe.c
+++ b/arch/ceva/src/common/up_stackframe.c
@@ -67,7 +67,7 @@
 
 FAR void *up_stack_frame(FAR struct tcb_s *tcb, size_t frame_size)
 {
-  FAR void *topaddr;
+  FAR void *ret;
 
   /* Align the frame_size */
 
@@ -82,15 +82,15 @@ FAR void *up_stack_frame(FAR struct tcb_s *tcb, size_t frame_size)
 
   /* Save the adjusted stack values in the struct tcb_s */
 
-  topaddr              = tcb->stack_base_ptr - frame_size;
-  tcb->stack_base_ptr  = topaddr;
+  ret = tcb->stack_base_ptr;
+  memset(ret, 0, frame_size);
+
+  /* Save the adjusted stack values in the struct tcb_s */
+
+  tcb->stack_base_ptr  = (FAR uint8_t *)tcb->stack_base_ptr + frame_size;
   tcb->adj_stack_size -= frame_size;
 
-  /* Reinitialize the task state after the stack is adjusted */
-
-  up_initial_state(tcb);
-
   /* And return the pointer to the allocated region */
 
-  return topaddr;
+  return ret;
 }
diff --git a/arch/ceva/src/common/up_usestack.c b/arch/ceva/src/common/up_usestack.c
index 85e1886629..0be0d51353 100644
--- a/arch/ceva/src/common/up_usestack.c
+++ b/arch/ceva/src/common/up_usestack.c
@@ -66,7 +66,7 @@
 
 int up_use_stack(FAR struct tcb_s *tcb, FAR void *stack, size_t stack_size)
 {
-  FAR void *top_of_stack;
+  uintptr_t top_of_stack;
   size_t size_of_stack;
 
 #ifdef CONFIG_TLS
@@ -101,12 +101,13 @@ int up_use_stack(FAR struct tcb_s *tcb, FAR void *stack, size_t stack_size)
    * boundary
    */
 
-  size_of_stack = STACK_ALIGN_DOWN(stack_size);
-  top_of_stack  = tcb->stack_alloc_ptr + size_of_stack;
+  top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
+  top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
+  size_of_stack = top_of_stack - (uintptr_t)tcb->stack_alloc_ptr;
 
   /* Save the adjusted stack values in the struct tcb_s */
 
-  tcb->stack_base_ptr = top_of_stack;
+  tcb->stack_base_ptr = tcb->stack_alloc_ptr;
   tcb->adj_stack_size = size_of_stack;
 
 #ifdef CONFIG_STACK_COLORATION
diff --git a/arch/misoc/src/lm32/lm32_usestack.c b/arch/misoc/src/lm32/lm32_usestack.c
index ffc13c9cb3..47e3a1449d 100644
--- a/arch/misoc/src/lm32/lm32_usestack.c
+++ b/arch/misoc/src/lm32/lm32_usestack.c
@@ -34,6 +34,8 @@
 #include <nuttx/arch.h>
 #include <nuttx/tls.h>
 
+#include "lm32.h"
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -98,19 +100,21 @@ int up_use_stack(struct tcb_s *tcb, void *stack, size_t stack_size)
   memset(tcb->stack_alloc_ptr, 0xaa, stack_size);
 #endif
 
-  /* The i486 uses a push-down stack:  the stack grows toward loweraddresses
-   * in memory.  The stack pointer register, points to the lowest, valid work
-   * address (the "top" of the stack).  Items on the stack are referenced as
-   * positive word offsets from sp.
+  /* LM32 uses a push-down stack:  the stack grows toward lower
+   * addresses in memory.  The stack pointer register points to the
+   * lowest, valid working address (the "top" of the stack).  Items on
+   * the stack are referenced as positive word offsets from sp.
    */
 
   top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
 
-  /* The i486 stack must be aligned at word (4 byte) boundaries. If necessary
-   * top_of_stack must be rounded down to the next boundary
+  /* The LM32 stack must be aligned at word (4 byte) boundaries; for
+   * floating point use, the stack must be aligned to 8-byte addresses.
+   * If necessary top_of_stack must be rounded down to the next
+   * boundary to meet these alignment requirements.
    */
 
-  top_of_stack &= ~3;
+  top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
   size_of_stack = top_of_stack - (uintptr_t)tcb->stack_alloc_ptr;
 
   /* Save the adjusted stack values in the struct tcb_s */
diff --git a/arch/misoc/src/minerva/minerva_usestack.c b/arch/misoc/src/minerva/minerva_usestack.c
index 6f30647464..00b5ea66f1 100644
--- a/arch/misoc/src/minerva/minerva_usestack.c
+++ b/arch/misoc/src/minerva/minerva_usestack.c
@@ -34,6 +34,8 @@
 #include <nuttx/arch.h>
 #include <nuttx/tls.h>
 
+#include "minerva.h"
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -98,19 +100,21 @@ int up_use_stack(struct tcb_s *tcb, void *stack, size_t stack_size)
   memset(tcb->stack_alloc_ptr, 0xaa, stack_size);
 #endif
 
-  /* The i486 uses a push-down stack:  the stack grows toward loweraddresses
-   * in memory.  The stack pointer register, points to the lowest, valid work
-   * address (the "top" of the stack).  Items on the stack are referenced as
-   * positive word offsets from sp.
+  /* MINERVA uses a push-down stack: the stack grows toward lower
+   * addresses in memory.  The stack pointer register points to the
+   * lowest, valid working address (the "top" of the stack).  Items on
+   * the stack are referenced as positive word offsets from sp.
    */
 
   top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
 
-  /* The i486 stack must be aligned at word (4 byte) boundaries. If necessary
-   * top_of_stack must be rounded down to the next boundary
+  /* The MINERVA stack must be aligned at word (4 byte) boundaries; for
+   * floating point use, the stack must be aligned to 8-byte addresses.
+   * If necessary top_of_stack must be rounded down to the next boundary
+   * to meet these alignment requirements.
    */
 
-  top_of_stack &= ~3;
+  top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
   size_of_stack = top_of_stack - (uintptr_t)tcb->stack_alloc_ptr;
 
   /* Save the adjusted stack values in the struct tcb_s */
diff --git a/arch/or1k/src/common/up_usestack.c b/arch/or1k/src/common/up_usestack.c
index e2740db43b..2e1993cb22 100644
--- a/arch/or1k/src/common/up_usestack.c
+++ b/arch/or1k/src/common/up_usestack.c
@@ -34,6 +34,8 @@
 #include <nuttx/arch.h>
 #include <nuttx/tls.h>
 
+#include "up_internal.h"
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -98,19 +100,8 @@ int up_use_stack(struct tcb_s *tcb, void *stack, size_t stack_size)
   memset(tcb->stack_alloc_ptr, 0xaa, stack_size);
 #endif
 
-  /* The i486 uses a push-down stack:  the stack grows toward loweraddresses
-   * in memory.  The stack pointer register, points to the lowest, valid work
-   * address (the "top" of the stack).  Items on the stack are referenced as
-   * positive word offsets from sp.
-   */
-
   top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
-
-  /* The i486 stack must be aligned at word (4 byte) boundaries. If necessary
-   * top_of_stack must be rounded down to the next boundary
-   */
-
-  top_of_stack &= ~3;
+  top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
   size_of_stack = top_of_stack - (uintptr_t)tcb->stack_alloc_ptr;
 
   /* Save the adjusted stack values in the struct tcb_s */
diff --git a/arch/sim/src/sim/up_createstack.c b/arch/sim/src/sim/up_createstack.c
index 558dbb14b7..6e540afd37 100644
--- a/arch/sim/src/sim/up_createstack.c
+++ b/arch/sim/src/sim/up_createstack.c
@@ -73,9 +73,6 @@
 
 int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
 {
-  FAR uint8_t *stack_alloc_ptr;
-  int ret = ERROR;
-
   stack_size += CONFIG_SIM_STACKSIZE_ADJUSTMENT;
 
 #ifdef CONFIG_TLS_ALIGNED
@@ -90,27 +87,49 @@ int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
     }
 #endif
 
-  /* Move up to next even word boundary if necessary */
+  /* Is there already a stack allocated of a different size?  Because of
+   * alignment issues, stack_size might erroneously appear to be of a
+   * different size.  Fortunately, this is not a critical operation.
+   */
 
-  size_t adj_stack_size = STACK_ALIGN_UP(stack_size);
+  if (tcb->stack_alloc_ptr && tcb->adj_stack_size != stack_size)
+    {
+      /* Yes.. Release the old stack */
 
-  /* Allocate the memory for the stack */
+      up_release_stack(tcb, ttype);
+    }
+
+  /* Do we need to allocate a new stack? */
+
+  if (!tcb->stack_alloc_ptr)
+    {
+      /* Allocate the stack.  If DEBUG is enabled (but not stack debug),
+       * then create a zeroed stack to make stack dumps easier to trace.
+       * If TLS is enabled, then we must allocate aligned stacks.
+       */
 
 #ifdef CONFIG_TLS_ALIGNED
-  stack_alloc_ptr = kumm_memalign(TLS_STACK_ALIGN, adj_stack_size);
+      tcb->stack_alloc_ptr = kumm_memalign(TLS_STACK_ALIGN, stack_size);
 #else
-  stack_alloc_ptr = kumm_malloc(adj_stack_size);
+      tcb->stack_alloc_ptr = kumm_malloc(stack_size);
 #endif
+    }
 
-  /* Was the allocation successful? */
+  /* Did we successfully allocate a stack? */
 
-  if (stack_alloc_ptr)
+  if (tcb->stack_alloc_ptr)
     {
+      uintptr_t top_of_stack;
+      size_t size_of_stack;
+
+      top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
+      top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
+      size_of_stack = top_of_stack - (uintptr_t)tcb->stack_alloc_ptr;
+
       /* Save the values in the TCB */
 
-      tcb->adj_stack_size  = adj_stack_size;
-      tcb->stack_alloc_ptr = stack_alloc_ptr;
-      tcb->stack_base_ptr  = tcb->stack_alloc_ptr;
+      tcb->stack_base_ptr = tcb->stack_alloc_ptr;
+      tcb->adj_stack_size = size_of_stack;
 
 #ifdef CONFIG_STACK_COLORATION
       /* If stack debug is enabled, then fill the stack with a
@@ -122,10 +141,10 @@ int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
 #endif /* CONFIG_STACK_COLORATION */
       tcb->flags |= TCB_FLAG_FREE_STACK;
 
-      ret = OK;
+      return OK;
     }
 
-  return ret;
+  return ERROR;
 }
 
 /****************************************************************************
diff --git a/arch/sim/src/sim/up_usestack.c b/arch/sim/src/sim/up_usestack.c
index 0f45fbc9d5..1c23d4719a 100644
--- a/arch/sim/src/sim/up_usestack.c
+++ b/arch/sim/src/sim/up_usestack.c
@@ -69,24 +69,36 @@
 int up_use_stack(FAR struct tcb_s *tcb, FAR void *stack, size_t stack_size)
 {
 #if CONFIG_SIM_STACKSIZE_ADJUSTMENT == 0
-  size_t adj_stack_size;
+  uintptr_t top_of_stack;
+  size_t size_of_stack;
 
 #ifdef CONFIG_TLS_ALIGNED
   /* Make certain that the user provided stack is properly aligned */
 
   DEBUGASSERT(((uintptr_t)stack & TLS_STACK_MASK) == 0);
 #endif
-  /* Move down to next even word boundary within the pre-allocated stack
-   * memory, if necessary.
-   */
 
-  adj_stack_size = STACK_ALIGN_DOWN(stack_size);
+  /* Is there already a stack allocated? */
 
-  /* Save the values in the TCB */
+  if (tcb->stack_alloc_ptr)
+    {
+      /* Yes.. Release the old stack allocation */
+
+      up_release_stack(tcb, tcb->flags & TCB_FLAG_TTYPE_MASK);
+    }
+
+  /* Save the new stack allocation */
 
-  tcb->adj_stack_size  = adj_stack_size;
   tcb->stack_alloc_ptr = stack;
-  tcb->stack_base_ptr  = tcb->stack_alloc_ptr;
+
+  /* Save the adjusted stack values in the struct tcb_s */
+
+  top_of_stack = (uintptr_t)tcb->stack_alloc_ptr + stack_size;
+  top_of_stack = STACK_ALIGN_DOWN(top_of_stack);
+  size_of_stack = top_of_stack - (uintptr_t)tcb->stack_alloc_ptr;
+
+  tcb->stack_base_ptr = tcb->stack_alloc_ptr;
+  tcb->adj_stack_size = size_of_stack;
 
 #if defined(CONFIG_STACK_COLORATION)
   /* If stack debug is enabled, then fill the stack with a
diff --git a/arch/sparc/src/common/up_createstack.c b/arch/sparc/src/common/up_createstack.c
index df9cb57e22..3dc94e69b8 100644
--- a/arch/sparc/src/common/up_createstack.c
+++ b/arch/sparc/src/common/up_createstack.c
@@ -105,14 +105,14 @@ int up_create_stack(FAR struct tcb_s *tcb, size_t stack_size, uint8_t ttype)
 
       if (ttype == TCB_FLAG_TTYPE_KERNEL)
         {
-          tcb->stack_alloc_ptr = (uint32_t *)kmm_malloc(stack_size);
+          tcb->stack_alloc_ptr = kmm_malloc(stack_size);
         }
       else
 #endif
         {
           /* Use the user-space allocator if this is a task or pthread */
 
-          tcb->stack_alloc_ptr = (uint32_t *)kumm_malloc(stack_size);
+          tcb->stack_alloc_ptr = kumm_malloc(stack_size);
         }
 
 #ifdef CONFIG_DEBUG_FEATURES