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doc: Emphasize the need for explicit RCU read-side markers

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This commit updates checklist.rst to emphasize the need for explicit
markers for RCU read-side critical sections.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-07-05 12:15:35 -07:00
parent 568035b01c
commit 4d2f862b5b
1 changed files with 7 additions and 2 deletions
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9
Documentation/RCU/checklist.rst
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@ -66,8 +66,13 @@ over a rather long period of time, but improvements are always welcome!
As a rough rule of thumb, any dereference of an RCU-protected
pointer must be covered by rcu_read_lock(), rcu_read_lock_bh(),
rcu_read_lock_sched(), or by the appropriate update-side lock.
Disabling of preemption can serve as rcu_read_lock_sched(), but
is less readable and prevents lockdep from detecting locking issues.
Explicit disabling of preemption (preempt_disable(), for example)
can serve as rcu_read_lock_sched(), but is less readable and
prevents lockdep from detecting locking issues.
Please not that you *cannot* rely on code known to be built
only in non-preemptible kernels. Such code can and will break,
especially in kernels built with CONFIG_PREEMPT_COUNT=y.
Letting RCU-protected pointers "leak" out of an RCU read-side
critical section is every bit as bad as letting them leak out