R Sricharan <[email protected]> writes: > From: Colin Cross <[email protected]> > > 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 <[email protected]> > Signed-off-by: R Sricharan <[email protected]>
Acked-by: Kevin Hilman <[email protected]> Tony, this should probably be queued up for v3.7-rc and flagged for stable. Thanks, Kevin > --- > [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); > } > > /** -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
