4 files changed, 30 insertions, 0 deletions

diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S
index 3c8821024509..915e12791836 100644
--- a/arch/ia64/kernel/entry.S
+++ b/arch/ia64/kernel/entry.S
@@ -470,6 +470,29 @@ ENTRY(load_switch_stack)
         br.cond.sptk.many b7
 END(load_switch_stack)
 
+GLOBAL_ENTRY(prefetch_stack)
+        add r14 = -IA64_SWITCH_STACK_SIZE, sp
+        add r15 = IA64_TASK_THREAD_KSP_OFFSET, in0
+        ;;
+        ld8 r16 = [r15]                         // load next's stack pointer
+        lfetch.fault.excl [r14], 128
+        ;;
+        lfetch.fault.excl [r14], 128
+        lfetch.fault [r16], 128
+        ;;
+        lfetch.fault.excl [r14], 128
+        lfetch.fault [r16], 128
+        ;;
+        lfetch.fault.excl [r14], 128
+        lfetch.fault [r16], 128
+        ;;
+        lfetch.fault.excl [r14], 128
+        lfetch.fault [r16], 128
+        ;;
+        lfetch.fault [r16], 128
+        br.ret.sptk.many rp
+END(prefetch_switch_stack)
+
 GLOBAL_ENTRY(execve)
         mov r15=__NR_execve                     // put syscall number in place
         break __BREAK_SYSCALL
diff --git a/include/asm-ia64/system.h b/include/asm-ia64/system.h
index 33256db4a7cf..635235fa1e32 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 ea1b5f32ec5c..c551e6a1447e 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;
diff --git a/kernel/sched.c b/kernel/sched.c
index 18b95520a2e2..2632b812cf24 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2888,6 +2888,7 @@ switch_tasks:
         if (next == rq->idle)
                 schedstat_inc(rq, sched_goidle);
         prefetch(next);
+        prefetch_stack(next);
         clear_tsk_need_resched(prev);
         rcu_qsctr_inc(task_cpu(prev));