[arch][kernel] handle default stack size better

-let arch define the default stack size in ARCH_DEFAULT_STACK_SIZE
-platform/target/project can override with CUSTOM_DEFAULT_STACK_SIZE

arch/arm/rules.mk

@@ -115,6 +115,9 @@ OBJS += \
 	$(LOCAL_DIR)/arm/mmu.o \
 	$(LOCAL_DIR)/arm/thread.o \
 	$(LOCAL_DIR)/arm/dcc.o
+
+DEFINES += \
+	ARCH_DEFAULT_STACK_SIZE=4096
 endif
 ifeq ($(SUBARCH),arm-m)
 OBJS += \
@@ -128,9 +131,8 @@ OBJS += \
 INCLUDES += \
 	-I$(LOCAL_DIR)/arm-m/CMSIS/CM3/CoreSupport
 
-# set a much smaller stack size
 DEFINES += \
-	DEFAULT_STACK_SIZE=1024
+	ARCH_DEFAULT_STACK_SIZE=1024
 endif
 
 # set the default toolchain to arm elf and set a #define

arch/x86/include/arch/defines.h

@@ -28,5 +28,7 @@
 // TODO: define to resolve to platform setup discovered value
 #define CACHE_LINE 32
 
+#define ARCH_DEFAULT_STACK_SIZE 8192
+
 #endif
 

include/kernel/thread.h

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008-2009 Travis Geiselbrecht
+ * Copyright (c) 2008-2012 Travis Geiselbrecht
  *
  * Permission is hereby granted, free of charge, to any person obtaining
  * a copy of this software and associated documentation files
@@ -26,6 +26,7 @@
 #include <sys/types.h>
 #include <list.h>
 #include <compiler.h>
+#include <arch/defines.h>
 #include <arch/ops.h>
 #include <arch/thread.h>
 
@@ -93,8 +94,10 @@ typedef struct thread {
 #define HIGH_PRIORITY ((NUM_PRIORITIES / 4) * 3)
 
 /* stack size */
-#ifndef DEFAULT_STACK_SIZE
-#define DEFAULT_STACK_SIZE 8192
+#ifdef CUSTOM_DEFAULT_STACK_SIZE
+#define DEFAULT_STACK_SIZE CUSTOM_DEFAULT_STACK_SIZE
+#else
+#define DEFAULT_STACK_SIZE ARCH_DEFAULT_STACK_SIZE
 #endif
 
 /* functions */