From mboxrd@z Thu Jan 1 00:00:00 1970 From: r.sricharan@ti.com (R Sricharan) Date: Wed, 12 Sep 2012 12:44:41 +0530 Subject: [PATCH V2] ARM: OMAP: counter: add locking to read_persistent_clock Message-ID: <1347434081-11469-1-git-send-email-r.sricharan@ti.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org From: Colin Cross 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 Signed-off-by: R Sricharan --- [V2] Added signed-off-by and looped in "linux-arm-kernel" list arch/arm/plat-omap/counter_32k.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) diff --git a/arch/arm/plat-omap/counter_32k.c b/arch/arm/plat-omap/counter_32k.c index dbf1e03..2bc51fb 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); } /** -- 1.7.9.5