rcu: Disable TASKS_RCU for usermode Linux
Usermode Linux currently does not implement arch_irqs_disabled_flags(),
which results in a build failure in TASKS_RCU. Therefore, this commit
disables the TASKS_RCU Kconfig option in usermode Linux builds. The
usermode Linux maintainers expect to merge arch_irqs_disabled_flags()
into 4.8, at which point this commit may be reverted.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Jeff Dike <jdike@addtoit.com>
Acked-by: Richard Weinberger <richard@nod.at>
Paul E. McKenney