> On Dec 12, 2023, at 12:27 PM, Neeraj Upadhyay (AMD) <[email protected]>
> wrote:
>
> 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:
Typo: necessary.
Probably no need to resend this one, just fix in the PR.
Thanks,
- Joel
> +
> + 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
>
>
