lkml.org 
[lkml]   [2023]   [Oct]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [RFC PATCH v3 1/5] tracing: Introduce faultable tracepoints (v3)
From
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@kernel.org> 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@kernel.org>
> 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@efficios.com>

Thanks!

Mathieu

> Reported-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
>
> 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

\
 
 \ /
  Last update: 2023-10-03 19:39    [W:0.059 / U:0.092 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site