ia64: Switch do_timer() to xtime_update()

local_cpu_data->itm_next = new_itm; does not need to be protected by
xtime_lock. xtime_update() takes the lock itself.

Signed-off-by: Torben Hohn <torbenh@gmx.de>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: johnstul@us.ibm.com
Cc: hch@infradead.org
Cc: yong.zhang0@gmail.com
LKML-Reference: <20110127145956.23248.49107.stgit@localhost>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

arch/ia64/kernel/time.c

@@ -190,19 +190,10 @@ timer_interrupt (int irq, void *dev_id)
 
 		new_itm += local_cpu_data->itm_delta;
 
-		if (smp_processor_id() == time_keeper_id) {
-			/*
-			 * Here we are in the timer irq handler. We have irqs locally
-			 * disabled, but we don't know if the timer_bh is running on
-			 * another CPU. We need to avoid to SMP race by acquiring the
-			 * xtime_lock.
-			 */
-			write_seqlock(&xtime_lock);
-			do_timer(1);
-			local_cpu_data->itm_next = new_itm;
-			write_sequnlock(&xtime_lock);
-		} else
-			local_cpu_data->itm_next = new_itm;
+		if (smp_processor_id() == time_keeper_id)
+			xtime_update(1);
+
+		local_cpu_data->itm_next = new_itm;
 
 		if (time_after(new_itm, ia64_get_itc()))
 			break;
@@ -222,7 +213,7 @@ timer_interrupt (int irq, void *dev_id)
 		 * comfort, we increase the safety margin by
 		 * intentionally dropping the next tick(s).  We do NOT
 		 * update itm.next because that would force us to call
-		 * do_timer() which in turn would let our clock run
+		 * xtime_update() which in turn would let our clock run
 		 * too fast (with the potentially devastating effect
 		 * of losing monotony of time).
 		 */

arch/ia64/xen/time.c

@@ -139,14 +139,11 @@ consider_steal_time(unsigned long new_itm)
 		run_posix_cpu_timers(p);
 		delta_itm += local_cpu_data->itm_delta * (stolen + blocked);
 
-		if (cpu == time_keeper_id) {
-			write_seqlock(&xtime_lock);
-			do_timer(stolen + blocked);
-			local_cpu_data->itm_next = delta_itm + new_itm;
-			write_sequnlock(&xtime_lock);
-		} else {
-			local_cpu_data->itm_next = delta_itm + new_itm;
-		}
+		if (cpu == time_keeper_id)
+			xtime_update(stolen + blocked);
+
+		local_cpu_data->itm_next = delta_itm + new_itm;
+
 		per_cpu(xen_stolen_time, cpu) += NS_PER_TICK * stolen;
 		per_cpu(xen_blocked_time, cpu) += NS_PER_TICK * blocked;
 	}