x86: move warning message of polling idle and HT enabled

The warning message at idle_setup() is never shown because
smp_num_sibling hasn't been updated at this point yet.

Move this polling idle and HT enabled warning to select_idle_routine().
I also implement this warning on 64-bit kernel.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 12 insertions, 5 deletions

diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index dbe0a846ec52..95313532b2e0 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -291,20 +291,27 @@ static int mwait_usable(const struct cpuinfo_x86 *c)
 
 void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)
 {
-        static int printed;
+        static int selected;
+
+        if (selected)
+                return;
+#ifdef CONFIG_X86_SMP
+        if (pm_idle == poll_idle && smp_num_siblings > 1) {
+                printk(KERN_WARNING "WARNING: polling idle and HT enabled,"
+                        " performance may degrade.\n");
+        }
+#endif
         if (cpu_has(c, X86_FEATURE_MWAIT) && mwait_usable(c)) {
                 /*
                  * Skip, if setup has overridden idle.
                  * One CPU supports mwait => All CPUs supports mwait
                  */
                 if (!pm_idle) {
-                        if (!printed) {
-                                printk(KERN_INFO "using mwait in idle threads.\n");
-                                printed = 1;
-                        }
+                        printk(KERN_INFO "using mwait in idle threads.\n");
                         pm_idle = mwait_idle;
                 }
         }
+        selected = 1;
 }
 
 static int __init idle_setup(char *str)