1 files changed, 29 insertions, 0 deletions

diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 5b7e736f3b49..028a2b95936c 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -249,3 +249,32 @@ time_init (void)
          */
         set_normalized_timespec(&wall_to_monotonic, -xtime.tv_sec, -xtime.tv_nsec);
 }
+
+#define SMALLUSECS 100
+
+void
+udelay (unsigned long usecs)
+{
+        unsigned long start;
+        unsigned long cycles;
+        unsigned long smallusecs;
+
+        /*
+         * Execute the non-preemptible delay loop (because the ITC might
+         * not be synchronized between CPUS) in relatively short time
+         * chunks, allowing preemption between the chunks.
+         */
+        while (usecs > 0) {
+                smallusecs = (usecs > SMALLUSECS) ? SMALLUSECS : usecs;
+                preempt_disable();
+                cycles = smallusecs*local_cpu_data->cyc_per_usec;
+                start = ia64_get_itc();
+
+                while (ia64_get_itc() - start < cycles)
+                        cpu_relax();
+
+                preempt_enable();
+                usecs -= smallusecs;
+        }
+}
+EXPORT_SYMBOL(udelay);