[PATCH] hrtimers: cleanup locking

Improve kernel/hrtimers.c locking: use a per-CPU base with a lock to control
locking of all clocks belonging to a CPU.  This simplifies code that needs to
lock all clocks at once.  This makes life easier for high-res timers and
dyntick.

No functional changes.

[ optimization change from Andrew Morton <akpm@osdl.org> ]

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, 28 insertions, 15 deletions

diff --git a/include/linux/hrtimer.h b/include/linux/hrtimer.h
index 44c7d280b1a5..e00fc4d3d74f 100644
--- a/include/linux/hrtimer.h
+++ b/include/linux/hrtimer.h
@@ -21,6 +21,9 @@
 #include <linux/list.h>
 #include <linux/wait.h>
 
+struct hrtimer_clock_base;
+struct hrtimer_cpu_base;
+
 /*
  * Mode arguments of xxx_hrtimer functions:
  */
@@ -37,8 +40,6 @@ enum hrtimer_restart {
         HRTIMER_RESTART,        /* Timer must be restarted */
 };
 
-struct hrtimer_base;
-
 /**
  * struct hrtimer - the basic hrtimer structure
  * @node:       red black tree node for time ordered insertion
@@ -51,10 +52,10 @@ struct hrtimer_base;
  * The hrtimer structure must be initialized by init_hrtimer_#CLOCKTYPE()
  */
 struct hrtimer {
-        struct rb_node          node;
-        ktime_t                 expires;
-        enum hrtimer_restart    (*function)(struct hrtimer *);
-        struct hrtimer_base     *base;
+        struct rb_node                  node;
+        ktime_t                         expires;
+        enum hrtimer_restart            (*function)(struct hrtimer *);
+        struct hrtimer_clock_base       *base;
 };
 
 /**
@@ -71,29 +72,41 @@ struct hrtimer_sleeper {
 
 /**
  * struct hrtimer_base - the timer base for a specific clock
- * @index:              clock type index for per_cpu support when moving a timer
- *                      to a base on another cpu.
- * @lock:               lock protecting the base and associated timers
+ * @index:              clock type index for per_cpu support when moving a
+ *                      timer to a base on another cpu.
  * @active:             red black tree root node for the active timers
  * @first:              pointer to the timer node which expires first
  * @resolution:         the resolution of the clock, in nanoseconds
  * @get_time:           function to retrieve the current time of the clock
  * @get_softirq_time:   function to retrieve the current time from the softirq
- * @curr_timer:         the timer which is executing a callback right now
  * @softirq_time:       the time when running the hrtimer queue in the softirq
- * @lock_key:           the lock_class_key for use with lockdep
  */
-struct hrtimer_base {
+struct hrtimer_clock_base {
+        struct hrtimer_cpu_base *cpu_base;
         clockid_t               index;
-        spinlock_t              lock;
         struct rb_root          active;
         struct rb_node          *first;
         ktime_t                 resolution;
         ktime_t                 (*get_time)(void);
         ktime_t                 (*get_softirq_time)(void);
-        struct hrtimer          *curr_timer;
         ktime_t                 softirq_time;
-        struct lock_class_key lock_key;
+};
+
+#define HRTIMER_MAX_CLOCK_BASES 2
+
+/*
+ * struct hrtimer_cpu_base - the per cpu clock bases
+ * @lock:               lock protecting the base and associated clock bases
+ *                      and timers
+ * @lock_key:           the lock_class_key for use with lockdep
+ * @clock_base:         array of clock bases for this cpu
+ * @curr_timer:         the timer which is executing a callback right now
+ */
+struct hrtimer_cpu_base {
+        spinlock_t                      lock;
+        struct lock_class_key           lock_key;
+        struct hrtimer_clock_base       clock_base[HRTIMER_MAX_CLOCK_BASES];
+        struct hrtimer                  *curr_timer;
 };
 
 /*