lkml.org 
[lkml]   [2012]   [Nov]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: [PATCH 055/270] ARM: OMAP: counter: add locking to read_persistent_clock
From
Date
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]
\
 
 \ /
  Last update: 2012-11-27 16:41    [W:1.155 / U:0.448 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site