rcu: Avoid misordering in __call_rcu_nocb_enqueue()
The NOCB leader wakeup ordering depends on the store to the header happening before the check for the leader already being awake. However, because atomic_long_add() does not return a value, it does not provide ordering guarantees, the incorrect comment in wake_nocb_leader() notwithstanding. This commit therefore adds a smp_mb__after_atomic() after the final atomic_long_add() to provide the needed ordering guarantee. Reported-by: NAmit Shah <amit.shah@redhat.com> Signed-off-by: NPaul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: NPaul Gortmaker <paul.gortmaker@windriver.com>
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