In switch_hrtimer_base() we are calling hrtimer_check_target() which guarantees this:

/* * With HIGHRES=y we do not migrate the timer when it is expiring * before the next event on the target cpu because we cannot reprogram * the target cpu hardware and we would cause it to fire late. * * Called with cpu_base->lock of target cpu held. */

But switch_hrtimer_base() is only called from one place, i.e. __hrtimer_start_range_ns() and at that point (where we call switch_hrtimer_base()) expiration time is not yet known as we call this routine later: hrtimer_set_expires_range_ns().

To fix this, we need to find the updated expiry time before calling switch_hrtimer_base().

Signed-off-by: Viresh Kumar viresh.kumar@linaro.org --- Hi Thomas,

I have sent this previously as part of: https://lkml.org/lkml/2014/4/4/23

But as you asked to send bugfixes without any dependencies for ticks patches, I thought of sending bugfixes separately for timers too. This was the only bugfix from that series and other patches don't conflict with it, so I am not resending other patches from above series again.

Not adding any stable tags as this is broken from a long long time and don't know if you want to fix it for those kernels.

kernel/hrtimer.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c index d55092c..c86b95a 100644 --- a/kernel/hrtimer.c +++ b/kernel/hrtimer.c @@ -968,11 +968,8 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim, /* 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 @@ -987,6 +984,9 @@ int __hrtimer_start_range_ns(struct hrtimer *timer, ktime_t tim,

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);