rcu_read_lock_bh_held - might we be in RCU-bh read-side critical section?
Check for bottom half being disabled, which covers both the CONFIG_PROVE_RCU and not cases. Note that if someone uses rcu_read_lock_bh, but then later enables BH, lockdep (if enabled) will show the situation. This is useful for debug checks in functions that require that they be called within an RCU read-side critical section.
Check debug_lockdep_rcu_enabled to prevent false positives during boot.
Note that rcu_read_lock is disallowed if the CPU is either idle or offline from an RCU perspective, so check for those as well.
|January 2017||Kernel Hackers Manual 4.8.|