diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
index 376fcbc..fd4f3be 100644
--- a/arch/ia64/kernel/perfmon.c
+++ b/arch/ia64/kernel/perfmon.c
@@ -1265,6 +1265,8 @@
 }
 EXPORT_SYMBOL(pfm_unregister_buffer_fmt);
 
+extern void update_pal_halt_status(int);
+
 static int
 pfm_reserve_session(struct task_struct *task, int is_syswide, unsigned int cpu)
 {
@@ -1311,6 +1313,11 @@
 		is_syswide,
 		cpu));
 
+	/*
+	 * disable default_idle() to go to PAL_HALT
+	 */
+	update_pal_halt_status(0);
+
 	UNLOCK_PFS(flags);
 
 	return 0;
@@ -1366,6 +1373,12 @@
 		is_syswide,
 		cpu));
 
+	/*
+	 * if possible, enable default_idle() to go into PAL_HALT
+	 */
+	if (pfm_sessions.pfs_task_sessions == 0 && pfm_sessions.pfs_sys_sessions == 0)
+		update_pal_halt_status(1);
+
 	UNLOCK_PFS(flags);
 
 	return 0;
diff --git a/arch/ia64/kernel/process.c b/arch/ia64/kernel/process.c
index c0140f4..474d75f 100644
--- a/arch/ia64/kernel/process.c
+++ b/arch/ia64/kernel/process.c
@@ -173,7 +173,9 @@
 		ia64_do_signal(oldset, scr, in_syscall);
 }
 
-static int pal_halt = 1;
+static int pal_halt        = 1;
+static int can_do_pal_halt = 1;
+
 static int __init nohalt_setup(char * str)
 {
 	pal_halt = 0;
@@ -181,16 +183,22 @@
 }
 __setup("nohalt", nohalt_setup);
 
+int
+update_pal_halt_status(int status)
+{
+	can_do_pal_halt = pal_halt && status;
+}
+
 /*
  * We use this if we don't have any better idle routine..
  */
 void
 default_idle (void)
 {
-	unsigned long pmu_active = ia64_getreg(_IA64_REG_PSR) & (IA64_PSR_PP | IA64_PSR_UP);
+	int can_do_pal;
 
 	while (!need_resched())
-		if (pal_halt && !pmu_active)
+		if (can_do_pal_halt)
 			safe_halt();
 		else
 			cpu_relax();