x86: clean up stack allocation and free

Clean up the allocation and freeing of stacks a bit by using a __GFP_ZERO flag
instead of memset.
Signed-off-by: Christoph Lameter <clameter@sgi.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Mike Travis <travis@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/asm-x86/thread_info_64.h

@@ -74,20 +74,14 @@ 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;							\
-    })
+#define THREAD_FLAGS (GFP_KERNEL | __GFP_ZERO)
 #else
-#define alloc_thread_info(tsk) \
-	((struct thread_info *) __get_free_pages(GFP_KERNEL,THREAD_ORDER))
+#define THREAD_FLAGS GFP_KERNEL
 #endif
 
+#define alloc_thread_info(tsk) \
+	((struct thread_info *) __get_free_pages(THREAD_FLAGS, THREAD_ORDER))
+
 #define free_thread_info(ti) free_pages((unsigned long) (ti), THREAD_ORDER)
 
 #else /* !__ASSEMBLY__ */