[PATCH 3.2 64/92] hrtimer: Set expiry time before switch_hrtimer_base()

From: Ben Hutchings
Date: Fri Jun 06 2014 - 21:33:28 EST


3.2.60-rc1 review patch. If anyone has any objections, please let me know.

------------------

From: Viresh Kumar <viresh.kumar@xxxxxxxxxx>

commit 84ea7fe37908254c3bd90910921f6e1045c1747a upstream.

switch_hrtimer_base() calls hrtimer_check_target() which ensures that
we do not migrate a timer to a remote cpu if the timer expires before
the current programmed expiry time on that remote cpu.

But __hrtimer_start_range_ns() calls switch_hrtimer_base() before the
new expiry time is set. So the sanity check in hrtimer_check_target()
is operating on stale or even uninitialized data.

Update expiry time before calling switch_hrtimer_base().

[ tglx: Rewrote changelog once again ]

Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Cc: linaro-kernel@xxxxxxxxxxxxxxxx
Cc: linaro-networking@xxxxxxxxxx
Cc: fweisbec@xxxxxxxxx
Cc: arvind.chauhan@xxxxxxx
Link: http://lkml.kernel.org/r/81999e148745fc51bbcd0615823fbab9b2e87e23.1399882253.git.viresh.kumar@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
kernel/hrtimer.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/kernel/hrtimer.c
+++ b/kernel/hrtimer.c
@@ -980,11 +980,8 @@ int __hrtimer_start_range_ns(struct hrti
/* Remove an active timer from the queue: */
ret = remove_hrtimer(timer, base);

- /* Switch the timer base, if necessary: */
- new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
-
if (mode & HRTIMER_MODE_REL) {
- tim = ktime_add_safe(tim, new_base->get_time());
+ tim = ktime_add_safe(tim, base->get_time());
/*
* CONFIG_TIME_LOW_RES is a temporary way for architectures
* to signal that they simply return xtime in
@@ -999,6 +996,9 @@ int __hrtimer_start_range_ns(struct hrti

hrtimer_set_expires_range_ns(timer, tim, delta_ns);

+ /* Switch the timer base, if necessary: */
+ new_base = switch_hrtimer_base(timer, base, mode & HRTIMER_MODE_PINNED);
+
timer_stats_hrtimer_set_start_info(timer);

leftmost = enqueue_hrtimer(timer, new_base);

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