[SPARC64]: Add support for CONFIG_DEBUG_STACK_USAGE.

arch/sparc64/Kconfig

@@ -633,6 +633,15 @@ config DEBUG_KERNEL
 	  Say Y here if you are developing drivers or trying to debug and
 	  identify kernel problems.
 
+config DEBUG_STACK_USAGE
+	bool "Enable stack utilization instrumentation"
+	depends on DEBUG_KERNEL
+	help
+	  Enables the display of the minimum amount of free stack which each
+	  task has ever had available in the sysrq-T and sysrq-P debug output.
+
+	  This option will slow down process creation somewhat.
+
 config DEBUG_SLAB
 	bool "Debug memory allocations"
 	depends on DEBUG_KERNEL

arch/sparc64/defconfig

@@ -905,7 +905,6 @@ CONFIG_IRDA_FAST_RR=y
 #
 # Old SIR device drivers
 #
-# CONFIG_IRPORT_SIR is not set
 
 #
 # Old Serial dongle support
@@ -1657,6 +1656,7 @@ CONFIG_OPROFILE=m
 # Kernel hacking
 #
 CONFIG_DEBUG_KERNEL=y
+# CONFIG_DEBUG_STACK_USAGE is not set
 # CONFIG_DEBUG_SLAB is not set
 CONFIG_MAGIC_SYSRQ=y
 # CONFIG_DEBUG_SPINLOCK is not set

include/asm-sparc64/thread_info.h

@@ -142,13 +142,30 @@ register struct thread_info *current_thread_info_reg asm("g6");
 
 /* thread information allocation */
 #if PAGE_SHIFT == 13
-#define alloc_thread_info(tsk)((struct thread_info *)__get_free_pages(GFP_KERNEL, 1))
-#define free_thread_info(ti)  free_pages((unsigned long)(ti),1)
+#define __THREAD_INFO_ORDER	1
 #else /* PAGE_SHIFT == 13 */
-#define alloc_thread_info(tsk)((struct thread_info *)__get_free_pages(GFP_KERNEL, 0))
-#define free_thread_info(ti)  free_pages((unsigned long)(ti),0)
+#define __THREAD_INFO_ORDER	0
 #endif /* PAGE_SHIFT == 13 */
 
+#ifdef CONFIG_DEBUG_STACK_USAGE
+#define alloc_thread_info(tsk)					\
+({								\
+	struct thread_info *ret;				\
+								\
+	ret = (struct thread_info *)				\
+	  __get_free_pages(GFP_KERNEL, __THREAD_INFO_ORDER);	\
+	if (ret)						\
+		memset(ret, 0, PAGE_SIZE<<__THREAD_INFO_ORDER);	\
+	ret;							\
+})
+#else
+#define alloc_thread_info(tsk) \
+	((struct thread_info *)__get_free_pages(GFP_KERNEL, __THREAD_INFO_ORDER))
+#endif
+
+#define free_thread_info(ti) \
+	free_pages((unsigned long)(ti),__THREAD_INFO_ORDER)
+
 #define __thread_flag_byte_ptr(ti)	\
 	((unsigned char *)(&((ti)->flags)))
 #define __cur_thread_flag_byte_ptr	__thread_flag_byte_ptr(current_thread_info())