[PATCH] tick-management: dyntick / highres functionality

With Ingo Molnar <mingo@elte.hu>

Add functions to provide dynamic ticks and high resolution timers.  The code
which keeps track of jiffies and handles the long idle periods is shared
between tick based and high resolution timer based dynticks.  The dyntick
functionality can be disabled on the kernel commandline.  Provide also the
infrastructure to support high resolution timers.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Cc: john stultz <johnstul@us.ibm.com>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 14 insertions, 6 deletions

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
index a2310d1bebe1..e04ef38ea3be 100644
--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -2,8 +2,8 @@
  *  linux/kernel/hrtimer.c
  *
  *  Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
- *  Copyright(C) 2005-2006, Red Hat, Inc., Ingo Molnar
- *  Copyright(C) 2006       Timesys Corp., Thomas Gleixner <tglx@timesys.com>
+ *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
+ *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner <tglx@timesys.com>
  *
  *  High-resolution kernel timers
  *
@@ -38,6 +38,7 @@
 #include <linux/notifier.h>
 #include <linux/syscalls.h>
 #include <linux/interrupt.h>
+#include <linux/tick.h>
 
 #include <asm/uaccess.h>
 
@@ -288,7 +289,7 @@ ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
 /*
  * Divide a ktime value by a nanosecond value
  */
-static unsigned long ktime_divns(const ktime_t kt, s64 div)
+unsigned long ktime_divns(const ktime_t kt, s64 div)
 {
         u64 dclc, inc, dns;
         int sft = 0;
@@ -305,9 +306,6 @@ static unsigned long ktime_divns(const ktime_t kt, s64 div)
 
         return (unsigned long) dclc;
 }
-
-#else /* BITS_PER_LONG < 64 */
-# define ktime_divns(kt, div)           (unsigned long)((kt).tv64 / (div))
 #endif /* BITS_PER_LONG >= 64 */
 
 /*
@@ -682,6 +680,16 @@ void hrtimer_run_queues(void)
         struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
         int i;
 
+        /*
+         * This _is_ ugly: We have to check in the softirq context,
+         * whether we can switch to highres and / or nohz mode. The
+         * clocksource switch happens in the timer interrupt with
+         * xtime_lock held. Notification from there only sets the
+         * check bit in the tick_oneshot code, otherwise we might
+         * deadlock vs. xtime_lock.
+         */
+        tick_check_oneshot_change(1);
+
         hrtimer_get_softirq_time(cpu_base);
 
         for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)