[PATCH] x86_64: x86_64 stack usage debugging

Applies to git & 2.6.17-rc6 after CONFIG_DEBUG_STACKOVERFLOW patch

uses same stack-zeroing mechanism as on i386 to discover maximum stack
excursions.
Signed-off-by: Eric Sandeen <sandeen@sgi.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/Kconfig.debug

@@ -42,6 +42,15 @@ config DEBUG_STACKOVERFLOW
 	  This option will cause messages to be printed if free stack space
 	  drops below a certain limit.
 
+config DEBUG_STACK_USAGE
+        bool "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 X86_REMOTE_DEBUG
 #       bool "kgdb debugging stub"
 

include/asm-x86_64/thread_info.h

@@ -73,8 +73,21 @@ static inline struct thread_info *stack_thread_info(void)
 }
 
 /* thread information allocation */
+#ifdef CONFIG_DEBUG_STACK_USAGE
+#define alloc_thread_info(tsk)					\
+    ({								\
+	struct thread_info *ret;				\
+								\
+	ret = ((struct thread_info *) __get_free_pages(GFP_KERNEL,THREAD_ORDER)); \
+	if (ret)						\
+		memset(ret, 0, THREAD_SIZE);			\
+	ret;							\
+    })
+#else
 #define alloc_thread_info(tsk) \
 	((struct thread_info *) __get_free_pages(GFP_KERNEL,THREAD_ORDER))
+#endif
+
 #define free_thread_info(ti) free_pages((unsigned long) (ti), THREAD_ORDER)
 
 #else /* !__ASSEMBLY__ */