rcu_read_lock_bh_held
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## Name

rcu_read_lock_bh_held — might we be in RCU-bh read-side critical section?

## Synopsis

`int rcu_read_lock_bh_held (` | void`)`;

## Arguments

`void`

  no arguments

## Description

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.

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