2 files changed, 6 insertions, 0 deletions

diff --git a/include/asm-ia64/system.h b/include/asm-ia64/system.h
index 33256db4a7c..635235fa1e3 100644
--- a/include/asm-ia64/system.h
+++ b/include/asm-ia64/system.h
@@ -275,6 +275,7 @@ extern void ia64_load_extra (struct task_struct *task);
  */
 #define __ARCH_WANT_UNLOCKED_CTXSW
 
+#define ARCH_HAS_PREFETCH_SWITCH_STACK
 #define ia64_platform_is(x) (strcmp(x, platform_name) == 0)
 
 void cpu_idle_wait(void);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index ea1b5f32ec5..c551e6a1447 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -604,6 +604,11 @@ extern int groups_search(struct group_info *group_info, gid_t grp);
 #define GROUP_AT(gi, i) \
     ((gi)->blocks[(i)/NGROUPS_PER_BLOCK][(i)%NGROUPS_PER_BLOCK])
 
+#ifdef ARCH_HAS_PREFETCH_SWITCH_STACK
+extern void prefetch_stack(struct task_struct*);
+#else
+static inline void prefetch_stack(struct task_struct *t) { }
+#endif
 
 struct audit_context;           /* See audit.c */
 struct mempolicy;