From: "Paul E. McKenney" <[email protected]> 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/[email protected]/ Reported-by: Steven Rostedt <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> Reviewed-by: Mathieu Desnoyers <[email protected]> Reviewed-by: Steven Rostedt (Google) <[email protected]> Signed-off-by: Neeraj Upadhyay (AMD) <[email protected]> --- Documentation/RCU/checklist.rst | 25 ++++++++++++++++--------- 1 file changed, 16 insertions(+), 9 deletions(-) diff --git a/Documentation/RCU/checklist.rst b/Documentation/RCU/checklist.rst index bd3c58c44bef..c432899aff22 100644 --- a/Documentation/RCU/checklist.rst +++ b/Documentation/RCU/checklist.rst @@ -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 primitives are the same as for their non-expedited counterparts. - If the updater uses call_rcu_tasks() or synchronize_rcu_tasks(), - then the readers must refrain from executing voluntary - context switches, that is, from blocking. If the updater uses - call_rcu_tasks_trace() or synchronize_rcu_tasks_trace(), then - the corresponding readers must use rcu_read_lock_trace() and - rcu_read_unlock_trace(). 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(). + Similarly, it is necssary to correctly use the RCU Tasks flavors: + + a. If the updater uses synchronize_rcu_tasks() or + call_rcu_tasks(), then the readers must refrain from + executing voluntary context switches, that is, from + blocking. + + b. If the updater uses call_rcu_tasks_trace() + 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 has even resulted in an exploitable security issue. Therefore, -- 2.40.1
