tree bd4b7b4e2e7db065c971eb264196f02e0b01ecff
parent 2515ddc6db8eb49a79f0fe5e67ff09ac7c81eab4
author Thomas Gleixner <tglx@linutronix.de> 1224613055 +0200
committer Thomas Gleixner <tglx@linutronix.de> 1224615204 +0200

NOHZ: fix thinko in the timer restart code path

commit fb02fbc14d17837b4b7b02dbb36142c16a7bf208 (NOHZ: restart tick
device from irq_enter())

solves the problem of stale jiffies when long running softirqs happen
in a long idle sleep period, but it has a major thinko in it:

When the interrupt which came in _is_ the timer interrupt which should
expire ts->sched_timer then we cancel and rearm the timer _before_ it
gets expired in hrtimer_interrupt() to the next period. That means the
call back function is not called. This game can go on for ever :(

Prevent this by making sure to only rearm the timer when the expiry
time is more than one tick_period away. Otherwise keep it running as
it is either already expired or will expiry at the right point to
update jiffies.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Venkatesch Pallipadi <venkatesh.pallipadi@intel.com>