rcu: Fix preemption mode check on synchronize_rcu[_expedited]()

An early check on synchronize_rcu[_expedited]() tries to determine if
the current CPU is in UP mode on an SMP no-preempt kernel, in which case
there is no need to start a grace period since the current assumed
quiescent state is all we need.

However the preemption mode doesn't take into account the boot selected
preemption mode under CONFIG_PREEMPT_DYNAMIC=y, missing a possible
early return if the running flavour is "none" or "voluntary".

Use the shiny new preempt mode accessors to fix this.  However,
avoid invoking them during early boot because doing so triggers a
WARN_ON_ONCE().

[ paulmck: Update for mainlined API. ]

Reported-by: Paul E. McKenney <[email protected]>
Signed-off-by: Frederic Weisbecker <[email protected]>
Cc: Uladzislau Rezki <[email protected]>
Cc: Joel Fernandes <[email protected]>
Cc: Boqun Feng <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Neeraj Upadhyay <[email protected]>
Cc: Valentin Schneider <[email protected]>
Signed-off-by: Paul E. McKenney <[email protected]>

0 files changed, 0 insertions, 0 deletions