[IA64] add missing cpu_relax() in ITC syncing code
David Mosberger-Tang [Mon, 25 Apr 2005 18:44:02 +0000 (11:44 -0700)]
Call cpu_relax() in busy-waiting loops of the ITC-syncing code.

Signed-off-by: David Mosberger-Tang <davidm@hpl.hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>

arch/ia64/kernel/smpboot.c

index ca1536d..dbc6b61 100644 (file)
@@ -1,7 +1,7 @@
 /*
  * SMP boot-related support
  *
- * Copyright (C) 1998-2003 Hewlett-Packard Co
+ * Copyright (C) 1998-2003, 2005 Hewlett-Packard Co
  *     David Mosberger-Tang <davidm@hpl.hp.com>
  *
  * 01/05/16 Rohit Seth <rohit.seth@intel.com>  Moved SMP booting functions from smp.c to here.
@@ -156,7 +156,8 @@ sync_master (void *arg)
        local_irq_save(flags);
        {
                for (i = 0; i < NUM_ROUNDS*NUM_ITERS; ++i) {
-                       while (!go[MASTER]);
+                       while (!go[MASTER])
+                               cpu_relax();
                        go[MASTER] = 0;
                        go[SLAVE] = ia64_get_itc();
                }
@@ -179,7 +180,8 @@ get_delta (long *rt, long *master)
        for (i = 0; i < NUM_ITERS; ++i) {
                t0 = ia64_get_itc();
                go[MASTER] = 1;
-               while (!(tm = go[SLAVE]));
+               while (!(tm = go[SLAVE]))
+                       cpu_relax();
                go[SLAVE] = 0;
                t1 = ia64_get_itc();
 
@@ -258,7 +260,8 @@ ia64_sync_itc (unsigned int master)
                return;
        }
 
-       while (go[MASTER]);     /* wait for master to be ready */
+       while (go[MASTER])
+               cpu_relax();    /* wait for master to be ready */
 
        spin_lock_irqsave(&itc_sync_lock, flags);
        {