rcu: Add Kconfig option to expedite grace periods during boot

This commit adds a CONFIG_RCU_EXPEDITE_BOOT Kconfig parameter
that emulates a very early boot rcu_expedite_gp().  A late-boot
call to rcu_end_inkernel_boot() will provide the corresponding
rcu_unexpedite_gp().  The late-boot call to rcu_end_inkernel_boot()
should be made just before init is spawned.

Reported-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
3 files changed