Re: [RFC PATCH v3 1/5] tracing: Introduce faultable tracepoints (v3)

[Mathieu Desnoyers]

On 10/3/23 13:33, Paul E. McKenney wrote:
> On Tue, Oct 03, 2023 at 10:08:54AM -0400, Steven Rostedt wrote:
> > On Tue, 3 Oct 2023 06:44:50 -0700
> > "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote:
> >
> > > > That way it is clear what uses what, as I read the original paragraph a
> > > > couple of times and could have sworn that rcu_read_lock_trace() required
> > > > tasks to not block.
> > >
> > > That would work for me.  Would you like to send a patch, or would you
> > > rather we made the adjustments?
> >
> > Which ever.
>
> OK, how about like this?
>
> 							Thanx, Paul
>
> ------------------------------------------------------------------------
>
> commit 973eb79ec46c16f13bb5b47ad14d44a1f1c79dc9
> Author: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Date:   Tue Oct 3 10:30:01 2023 -0700
>
>      doc: Clarify RCU Tasks reader/updater checklist
>      
>      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.
>      

Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>

Thanks!

Mathieu

>      Reported-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
>      Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
>
> 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,

--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com