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| author | Colin Cross <ccross@android.com> | 2012-10-08 14:01:12 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-12-03 11:47:23 -0800 |
| commit | e84ad739d8a2143e5cd284a4c0462278587e4aa3 (patch) | |
| tree | 923ceb6136a4e877fff38bbaa504d055308f229a | |
| parent | fc6058e1a4cc1f76aab5c580322e109cf448ec9b (diff) | |
| download | linux-3.10-e84ad739d8a2143e5cd284a4c0462278587e4aa3.tar.gz linux-3.10-e84ad739d8a2143e5cd284a4c0462278587e4aa3.tar.bz2 linux-3.10-e84ad739d8a2143e5cd284a4c0462278587e4aa3.zip | |
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>
| -rw-r--r-- | arch/arm/plat-omap/counter_32k.c | 21 |
1 files changed, 14 insertions, 7 deletions
diff --git a/arch/arm/plat-omap/counter_32k.c b/arch/arm/plat-omap/counter_32k.c index 5068fe5a691..fd433e7a25f 100644 --- a/arch/arm/plat-omap/counter_32k.c +++ b/arch/arm/plat-omap/counter_32k.c @@ -50,22 +50,29 @@ 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); + 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(&persistent_ts, nsecs); + + *ts = persistent_ts; - timespec_add_ns(tsp, nsecs); - *ts = *tsp; + spin_unlock_irqrestore(&read_persistent_clock_lock, flags); } int __init omap_init_clocksource_32k(void) |