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| author | Colin Cross <ccross@android.com> | 2012-10-08 14:01:12 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-10-21 09:32:39 -0700 |
| commit | d16325665f213bfb893c978f54d43b142a0daecd (patch) | |
| tree | 35e22bbd95cfedf20bfaddb1d90140a7f1a89dfd /arch | |
| parent | 9d03830aa8319e80d33e021f6a3f8ffe1adbe780 (diff) | |
| download | lwn-d16325665f213bfb893c978f54d43b142a0daecd.tar.gz lwn-d16325665f213bfb893c978f54d43b142a0daecd.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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -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 dbf1e03029a5..2bc51fb1f717 100644 --- a/arch/arm/plat-omap/counter_32k.c +++ b/arch/arm/plat-omap/counter_32k.c @@ -55,22 +55,29 @@ 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(&persistent_ts, nsecs); + + *ts = persistent_ts; - timespec_add_ns(tsp, nsecs); - *ts = *tsp; + spin_unlock_irqrestore(&read_persistent_clock_lock, flags); } /** |