Commit 3cf50161 authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Boqun Feng
Browse files

doc: Make checklist.rst note that spinlocks are implied RCU readers 



In kernels built with CONFIG_PREEMPT_RT=n, spinlock critical sections
are RCU readers because they disable preemption.  However, they are also
RCU readers in CONFIG_PREEMPT_RT=y because in that case the locking
primitives contain rcu_read_lock() and rcu_read_unlock().  Therefore,
upgrade checklist.rst to document this non-obvious case.

While in the area, fix a typo by changing "read-side critical" to
"read-side critical section".

Signed-off-by: default avatarPaul E. McKenney <paulmck@kernel.org>
Signed-off-by: default avatarBoqun Feng <boqun.feng@gmail.com>
parent 8dbc33b4

Documentation/RCU/checklist.rst

+3 −2
Original line number Diff line number Diff line
@@ -68,7 +68,8 @@ over a rather long period of time, but improvements are always welcome! 
	rcu_read_lock_sched(), or by the appropriate update-side lock.

	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.

	prevents lockdep from detecting locking issues.  Acquiring a

	spinlock also enters an RCU read-side critical section.



	Please note that you *cannot* rely on code known to be built

	only in non-preemptible kernels.  Such code can and will break,
@@ -444,7 +445,7 @@ over a rather long period of time, but improvements are always welcome! 
	real-time workloads than is synchronize_rcu_expedited().



	It is also permissible to sleep in RCU Tasks Trace read-side

	critical, which are delimited by rcu_read_lock_trace() and

	critical section, which are delimited by rcu_read_lock_trace() and

	rcu_read_unlock_trace().  However, this is a specialized flavor

	of RCU, and you should not use it without first checking with

	its current users.  In most cases, you should instead use SRCU.