[ARM] 3554/1: ARM: Fix dyntick locking

Patch from Tony Lindgren

This patch fixes some dyntick locking issues on ARM as pointed
out by Russell King.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 20 insertions, 9 deletions

diff --git a/arch/arm/kernel/irq.c b/arch/arm/kernel/irq.c
index 2d5896b36181..bcc19fbb32df 100644
--- a/arch/arm/kernel/irq.c
+++ b/arch/arm/kernel/irq.c
@@ -342,10 +342,10 @@ __do_irq(unsigned int irq, struct irqaction *action, struct pt_regs *regs)
 
 #ifdef CONFIG_NO_IDLE_HZ
         if (!(action->flags & SA_TIMER) && system_timer->dyn_tick != NULL) {
-                write_seqlock(&xtime_lock);
+                spin_lock(&system_timer->dyn_tick->lock);
                 if (system_timer->dyn_tick->state & DYN_TICK_ENABLED)
                         system_timer->dyn_tick->handler(irq, 0, regs);
-                write_sequnlock(&xtime_lock);
+                spin_unlock(&system_timer->dyn_tick->lock);
         }
 #endif
 
diff --git a/arch/arm/kernel/time.c b/arch/arm/kernel/time.c
index d6bd435a6857..9c12d4fefbd3 100644
--- a/arch/arm/kernel/time.c
+++ b/arch/arm/kernel/time.c
@@ -379,7 +379,7 @@ static int timer_dyn_tick_enable(void)
         int ret = -ENODEV;
 
         if (dyn_tick) {
-                write_seqlock_irqsave(&xtime_lock, flags);
+                spin_lock_irqsave(&dyn_tick->lock, flags);
                 ret = 0;
                 if (!(dyn_tick->state & DYN_TICK_ENABLED)) {
                         ret = dyn_tick->enable();
@@ -387,7 +387,7 @@ static int timer_dyn_tick_enable(void)
                         if (ret == 0)
                                 dyn_tick->state |= DYN_TICK_ENABLED;
                 }
-                write_sequnlock_irqrestore(&xtime_lock, flags);
+                spin_unlock_irqrestore(&dyn_tick->lock, flags);
         }
 
         return ret;
@@ -400,7 +400,7 @@ static int timer_dyn_tick_disable(void)
         int ret = -ENODEV;
 
         if (dyn_tick) {
-                write_seqlock_irqsave(&xtime_lock, flags);
+                spin_lock_irqsave(&dyn_tick->lock, flags);
                 ret = 0;
                 if (dyn_tick->state & DYN_TICK_ENABLED) {
                         ret = dyn_tick->disable();
@@ -408,7 +408,7 @@ static int timer_dyn_tick_disable(void)
                         if (ret == 0)
                                 dyn_tick->state &= ~DYN_TICK_ENABLED;
                 }
-                write_sequnlock_irqrestore(&xtime_lock, flags);
+                spin_unlock_irqrestore(&dyn_tick->lock, flags);
         }
 
         return ret;
@@ -422,15 +422,20 @@ static int timer_dyn_tick_disable(void)
 void timer_dyn_reprogram(void)
 {
         struct dyn_tick_timer *dyn_tick = system_timer->dyn_tick;
-        unsigned long next, seq;
+        unsigned long next, seq, flags;
 
-        if (dyn_tick && (dyn_tick->state & DYN_TICK_ENABLED)) {
+        if (!dyn_tick)
+                return;
+
+        spin_lock_irqsave(&dyn_tick->lock, flags);
+        if (dyn_tick->state & DYN_TICK_ENABLED) {
                 next = next_timer_interrupt();
                 do {
                         seq = read_seqbegin(&xtime_lock);
-                        dyn_tick->reprogram(next_timer_interrupt() - jiffies);
+                        dyn_tick->reprogram(next - jiffies);
                 } while (read_seqretry(&xtime_lock, seq));
         }
+        spin_unlock_irqrestore(&dyn_tick->lock, flags);
 }
 
 static ssize_t timer_show_dyn_tick(struct sys_device *dev, char *buf)
@@ -499,5 +504,10 @@ void __init time_init(void)
         if (system_timer->offset == NULL)
                 system_timer->offset = dummy_gettimeoffset;
         system_timer->init();
+
+#ifdef CONFIG_NO_IDLE_HZ
+        if (system_timer->dyn_tick)
+                system_timer->dyn_tick->lock = SPIN_LOCK_UNLOCKED;
+#endif
 }
 
diff --git a/include/asm-arm/mach/time.h b/include/asm-arm/mach/time.h
index 96c6db7dd0e1..9f28073559e8 100644
--- a/include/asm-arm/mach/time.h
+++ b/include/asm-arm/mach/time.h
@@ -50,6 +50,7 @@ struct sys_timer {
 #define DYN_TICK_ENABLED        (1 << 1)
 
 struct dyn_tick_timer {
+        spinlock_t      lock;
         unsigned int    state;                  /* Current state */
         int             (*enable)(void);        /* Enables dynamic tick */
         int             (*disable)(void);       /* Disables dynamic tick */