timers: Avoid an unnecessary iteration in __run_timers()

timers: Avoid an unnecessary iteration in __run_timers()

If the base clock is behind jiffies in the soft irq expiry code then the
next timer is retrieved by get_next_timer_interrupt() to avoid incrementing
base clock one by one. If the next timer interrupt is past current jiffies
then the base clock is set to jiffies - 1. At the call site this is
incremented and another iteration through the expiry loop is executed which
checks empty hash buckets.

That's a pointless excercise because it's already known that the next timer
is past jiffies.

Set the base clock in that case to jiffies directly so it gets incremented
to jiffies + 1 at the call site resulting in immediate termination of the
expiry loop.

[ tglx: Massaged changelog and added comment to the code ]

Signed-off-by: Zhenzhong Duan <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Acked-by: Anna-Maria Gleixner <[email protected]>
Cc: Joe Jin <[email protected]>
Cc: [email protected]
Cc: Srinivas Reddy Eeda <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/7086a857-f90c-4616-bbe8-f7696f21626c@default