From: Joel Fernandes <joel@joelfernandes.org>
To: "Neeraj Upadhyay (AMD)" <neeraj.iitr10@gmail.com>
Cc: rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
kernel-team@meta.com, rostedt@goodmis.org, paulmck@kernel.org,
Neeraj.Upadhyay@amd.com,
Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Subject: Re: [PATCH rcu 3/5] doc: Clarify RCU Tasks reader/updater checklist
Date: Tue, 12 Dec 2023 15:09:28 -0500 [thread overview]
Message-ID: <019C4075-EDA3-48A9-8762-CBB28D0BA37C@joelfernandes.org> (raw)
In-Reply-To: <20231212172653.11485-3-neeraj.iitr10@gmail.com>
> On Dec 12, 2023, at 12:27 PM, Neeraj Upadhyay (AMD) <neeraj.iitr10@gmail.com> wrote:
>
> From: "Paul E. McKenney" <paulmck@kernel.org>
>
> 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>
> ---
> 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
>
>
next prev parent reply other threads:[~2023-12-12 20:09 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-12 17:23 [PATCH rcu 0/5] Documentation updates for v6.8 Neeraj Upadhyay (AMD)
2023-12-12 17:26 ` [PATCH rcu 1/5] Documentation: RCU: Remove repeated word in comments Neeraj Upadhyay (AMD)
2023-12-12 17:26 ` [PATCH rcu 2/5] rculist.h: docs: Fix wrong function summary Neeraj Upadhyay (AMD)
2023-12-12 17:26 ` [PATCH rcu 3/5] doc: Clarify RCU Tasks reader/updater checklist Neeraj Upadhyay (AMD)
2023-12-12 20:09 ` Joel Fernandes [this message]
2023-12-12 17:26 ` [PATCH rcu 4/5] doc: Mention address and data dependencies in rcu_dereference.rst Neeraj Upadhyay (AMD)
2023-12-12 17:26 ` [PATCH rcu 5/5] doc: Clarify historical disclaimers in memory-barriers.txt Neeraj Upadhyay (AMD)
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