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doc: Clarify RCU Tasks reader/updater checklist

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Currently, the reader/updater compatibility rules for the three RCU
Tasks flavors are squished together in a single paragraph, which can
result in confusion.  This commit therefore splits them out into a list,
clearly showing the distinction between these flavors.

Link: https://lore.kernel.org/all/20231002211936.5948253e@gandalf.local.home/

Reported-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com>
This commit is contained in:
Paul E. McKenney 2023-10-03 10:30:01 -07:00 committed by Neeraj Upadhyay (AMD)
parent 493dffa3ab
commit 1b7178b23d
1 changed files with 16 additions and 9 deletions
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25
Documentation/RCU/checklist.rst
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@ -241,15 +241,22 @@ over a rather long period of time, but improvements are always welcome!
srcu_struct. The rules for the expedited RCU grace-period-wait srcu_struct. The rules for the expedited RCU grace-period-wait
primitives are the same as for their non-expedited counterparts. primitives are the same as for their non-expedited counterparts.
If the updater uses call_rcu_tasks() or synchronize_rcu_tasks(), Similarly, it is necessary to correctly use the RCU Tasks flavors:
then the readers must refrain from executing voluntary
context switches, that is, from blocking. If the updater uses a. If the updater uses synchronize_rcu_tasks() or
call_rcu_tasks_trace() or synchronize_rcu_tasks_trace(), then call_rcu_tasks(), then the readers must refrain from
the corresponding readers must use rcu_read_lock_trace() and executing voluntary context switches, that is, from
rcu_read_unlock_trace(). If an updater uses call_rcu_tasks_rude() blocking.
or synchronize_rcu_tasks_rude(), then the corresponding readers
must use anything that disables preemption, for example, b. If the updater uses call_rcu_tasks_trace()
preempt_disable() and preempt_enable(). or synchronize_rcu_tasks_trace(), then the
corresponding readers must use rcu_read_lock_trace()
and rcu_read_unlock_trace().
c. If an updater uses call_rcu_tasks_rude() or
synchronize_rcu_tasks_rude(), then the corresponding
readers must use anything that disables preemption,
for example, preempt_disable() and preempt_enable().
Mixing things up will result in confusion and broken kernels, and Mixing things up will result in confusion and broken kernels, and
has even resulted in an exploitable security issue. Therefore, has even resulted in an exploitable security issue. Therefore,