ARM: OMAP: counter: add locking to read_persistent_clock
commit 9d7d6e363b06934221b81a859d509844c97380df upstream.
read_persistent_clock uses a global variable, use a spinlock to
ensure non-atomic updates to the variable don't overlap and cause
time to move backwards.
Signed-off-by: Colin Cross <ccross@android.com>
Signed-off-by: R Sricharan <r.sricharan@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/arm/plat-omap/counter_32k.c b/arch/arm/plat-omap/counter_32k.c
index 5068fe5..fd433e7 100644
--- a/arch/arm/plat-omap/counter_32k.c
+++ b/arch/arm/plat-omap/counter_32k.c
@@ -50,22 +50,29 @@
* nsecs and adds to a monotonically increasing timespec.
*/
static struct timespec persistent_ts;
-static cycles_t cycles, last_cycles;
+static cycles_t cycles;
static unsigned int persistent_mult, persistent_shift;
+static DEFINE_SPINLOCK(read_persistent_clock_lock);
+
void read_persistent_clock(struct timespec *ts)
{
unsigned long long nsecs;
- cycles_t delta;
- struct timespec *tsp = &persistent_ts;
+ cycles_t last_cycles;
+ unsigned long flags;
+
+ spin_lock_irqsave(&read_persistent_clock_lock, flags);
last_cycles = cycles;
cycles = timer_32k_base ? __raw_readl(timer_32k_base) : 0;
- delta = cycles - last_cycles;
- nsecs = clocksource_cyc2ns(delta, persistent_mult, persistent_shift);
+ nsecs = clocksource_cyc2ns(cycles - last_cycles,
+ persistent_mult, persistent_shift);
- timespec_add_ns(tsp, nsecs);
- *ts = *tsp;
+ timespec_add_ns(&persistent_ts, nsecs);
+
+ *ts = persistent_ts;
+
+ spin_unlock_irqrestore(&read_persistent_clock_lock, flags);
}
int __init omap_init_clocksource_32k(void)