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ARM: OMAP: counter: add locking to read_persistent_clock

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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>
Cc: stable@vger.kernel.org
Signed-off-by: Tony Lindgren <tony@atomide.com>
This commit is contained in:
Colin Cross 2012-10-08 14:01:12 -07:00 committed by Tony Lindgren
parent 5e090ed7af
commit 9d7d6e363b
1 changed files with 14 additions and 7 deletions
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21
arch/arm/plat-omap/counter_32k.c
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@ -52,22 +52,29 @@ static u32 notrace omap_32k_read_sched_clock(void)
* 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);
static void omap_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 = sync32k_cnt_reg ? __raw_readl(sync32k_cnt_reg) : 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);
}
/**