| Subject | Re: [PATCH 055/270] ARM: OMAP: counter: add locking to read_persistent_clock | From | Ben Hutchings <> | Date | Tue, 27 Nov 2012 15:05:20 +0000 |
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On Mon, 2012-11-26 at 14:55 -0200, Herton Ronaldo Krzesinski wrote: > 3.5.7u1 -stable review patch. If anyone has any objections, please let me know. > > ------------------ > > From: Colin Cross <ccross@android.com> > > 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: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com> [...]
This is also missing from 3.4. I'm attaching the adjusted version for 3.2, which looks like it will work for 3.4.
Ben.
-- Ben Hutchings Never attribute to conspiracy what can adequately be explained by stupidity. From: Colin Cross <ccross@android.com> Date: Mon, 8 Oct 2012 14:01:12 -0700 Subject: 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> --- arch/arm/plat-omap/counter_32k.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
--- a/arch/arm/plat-omap/counter_32k.c +++ b/arch/arm/plat-omap/counter_32k.c @@ -82,22 +82,29 @@ static void notrace omap_update_sched_cl * 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)[unhandled content-type:application/pgp-signature] |