2 files changed, 58 insertions, 8 deletions

diff --git a/include/linux/timer.h b/include/linux/timer.h
index 719113b652dd..e0c5c16c992f 100644
--- a/include/linux/timer.h
+++ b/include/linux/timer.h
@@ -37,6 +37,7 @@ extern struct tvec_t_base_s boot_tvec_bases;
                 TIMER_INITIALIZER(_function, _expires, _data)
 
 void fastcall init_timer(struct timer_list * timer);
+void fastcall init_timer_deferrable(struct timer_list *timer);
 
 static inline void setup_timer(struct timer_list * timer,
                                 void (*function)(unsigned long),
diff --git a/kernel/timer.c b/kernel/timer.c
index b22bd39740dd..dbe966feff2f 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -74,7 +74,7 @@ struct tvec_t_base_s {
         tvec_t tv3;
         tvec_t tv4;
         tvec_t tv5;
-} ____cacheline_aligned_in_smp;
+} ____cacheline_aligned;
 
 typedef struct tvec_t_base_s tvec_base_t;
 
@@ -82,6 +82,37 @@ tvec_base_t boot_tvec_bases;
 EXPORT_SYMBOL(boot_tvec_bases);
 static DEFINE_PER_CPU(tvec_base_t *, tvec_bases) = &boot_tvec_bases;
 
+/*
+ * Note that all tvec_bases is 2 byte aligned and lower bit of
+ * base in timer_list is guaranteed to be zero. Use the LSB for
+ * the new flag to indicate whether the timer is deferrable
+ */
+#define TBASE_DEFERRABLE_FLAG           (0x1)
+
+/* Functions below help us manage 'deferrable' flag */
+static inline unsigned int tbase_get_deferrable(tvec_base_t *base)
+{
+        return ((unsigned int)(unsigned long)base & TBASE_DEFERRABLE_FLAG);
+}
+
+static inline tvec_base_t *tbase_get_base(tvec_base_t *base)
+{
+        return ((tvec_base_t *)((unsigned long)base & ~TBASE_DEFERRABLE_FLAG));
+}
+
+static inline void timer_set_deferrable(struct timer_list *timer)
+{
+        timer->base = ((tvec_base_t *)((unsigned long)(timer->base) |
+                                       TBASE_DEFERRABLE_FLAG));
+}
+
+static inline void
+timer_set_base(struct timer_list *timer, tvec_base_t *new_base)
+{
+        timer->base = (tvec_base_t *)((unsigned long)(new_base) |
+                                      tbase_get_deferrable(timer->base));
+}
+
 /**
  * __round_jiffies - function to round jiffies to a full second
  * @j: the time in (absolute) jiffies that should be rounded
@@ -295,6 +326,13 @@ void fastcall init_timer(struct timer_list *timer)
 }
 EXPORT_SYMBOL(init_timer);
 
+void fastcall init_timer_deferrable(struct timer_list *timer)
+{
+        init_timer(timer);
+        timer_set_deferrable(timer);
+}
+EXPORT_SYMBOL(init_timer_deferrable);
+
 static inline void detach_timer(struct timer_list *timer,
                                 int clear_pending)
 {
@@ -325,10 +363,11 @@ static tvec_base_t *lock_timer_base(struct timer_list *timer,
         tvec_base_t *base;
 
         for (;;) {
-                base = timer->base;
+                tvec_base_t *prelock_base = timer->base;
+                base = tbase_get_base(prelock_base);
                 if (likely(base != NULL)) {
                         spin_lock_irqsave(&base->lock, *flags);
-                        if (likely(base == timer->base))
+                        if (likely(prelock_base == timer->base))
                                 return base;
                         /* The timer has migrated to another CPU */
                         spin_unlock_irqrestore(&base->lock, *flags);
@@ -365,11 +404,11 @@ int __mod_timer(struct timer_list *timer, unsigned long expires)
                  */
                 if (likely(base->running_timer != timer)) {
                         /* See the comment in lock_timer_base() */
-                        timer->base = NULL;
+                        timer_set_base(timer, NULL);
                         spin_unlock(&base->lock);
                         base = new_base;
                         spin_lock(&base->lock);
-                        timer->base = base;
+                        timer_set_base(timer, base);
                 }
         }
 
@@ -397,7 +436,7 @@ void add_timer_on(struct timer_list *timer, int cpu)
         timer_stats_timer_set_start_info(timer);
         BUG_ON(timer_pending(timer) || !timer->function);
         spin_lock_irqsave(&base->lock, flags);
-        timer->base = base;
+        timer_set_base(timer, base);
         internal_add_timer(base, timer);
         spin_unlock_irqrestore(&base->lock, flags);
 }
@@ -550,7 +589,7 @@ static int cascade(tvec_base_t *base, tvec_t *tv, int index)
          * don't have to detach them individually.
          */
         list_for_each_entry_safe(timer, tmp, &tv_list, entry) {
-                BUG_ON(timer->base != base);
+                BUG_ON(tbase_get_base(timer->base) != base);
                 internal_add_timer(base, timer);
         }
 
@@ -636,6 +675,9 @@ static unsigned long __next_timer_interrupt(tvec_base_t *base)
         index = slot = timer_jiffies & TVR_MASK;
         do {
                 list_for_each_entry(nte, base->tv1.vec + slot, entry) {
+                        if (tbase_get_deferrable(nte->base))
+                                continue;
+
                         found = 1;
                         expires = nte->expires;
                         /* Look at the cascade bucket(s)? */
@@ -1617,6 +1659,13 @@ static int __devinit init_timers_cpu(int cpu)
                                                 cpu_to_node(cpu));
                         if (!base)
                                 return -ENOMEM;
+
+                        /* Make sure that tvec_base is 2 byte aligned */
+                        if (tbase_get_deferrable(base)) {
+                                WARN_ON(1);
+                                kfree(base);
+                                return -ENOMEM;
+                        }
                         memset(base, 0, sizeof(*base));
                         per_cpu(tvec_bases, cpu) = base;
                 } else {
@@ -1658,7 +1707,7 @@ static void migrate_timer_list(tvec_base_t *new_base, struct list_head *head)
         while (!list_empty(head)) {
                 timer = list_entry(head->next, struct timer_list, entry);
                 detach_timer(timer, 0);
-                timer->base = new_base;
+                timer_set_base(timer, new_base);
                 internal_add_timer(new_base, timer);
         }
 }