rcu: Add RCU_GET_STATE_NOT_TRACKED for subsystems without expedited GPs

SRCU and Tasks RCU do not track expedited grace periods. When their
callback state is checked via poll_state_synchronize_rcu_full(), the
uninitialized or zeroed exp field could cause false-positive
completion detection.

This commit adds an RCU_GET_STATE_NOT_TRACKED sentinel value (0x2) that
these subsystems can place into exp to indicate that expedited GP
tracking is not applicable. The expedited sequence check in
poll_state_synchronize_rcu_full() is guarded to skip entries marked with
this sentinel.

This is needed to allow rcu_segcblist_advance() and rcu_accelerate_cbs()
to work with both normal and expedited grace periods via
get_state_synchronize_rcu_full() and poll_state_synchronize_rcu_full().

Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Reviewed-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

0 files changed, 0 insertions, 0 deletions