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From: Joel Fernandes <joel@joelfernandes.org>
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Subject: Re: [PATCH 02/10] rcu: Move rcu_preempt_depth_set() to rcupdate.h
Date: Sun, 31 Mar 2024 16:39:54 +0530
Message-Id: <769AEAAB-7DEA-4D94-8979-F01EDFD6EE46@joelfernandes.org>
References: <20240328075318.83039-3-jiangshanlai@gmail.com>
Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org, x86@kernel.org,
 Lai Jiangshan <jiangshan.ljs@antgroup.com>,
 "Paul E. McKenney" <paulmck@kernel.org>,
 Peter Zijlstra <peterz@infradead.org>,
 Frederic Weisbecker <frederic@kernel.org>,
 Neeraj Upadhyay <quic_neeraju@quicinc.com>,
 Josh Triplett <josh@joshtriplett.org>, Boqun Feng <boqun.feng@gmail.com>,
 Steven Rostedt <rostedt@goodmis.org>,
 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 Zqiang <qiang.zhang1211@gmail.com>
In-Reply-To: <20240328075318.83039-3-jiangshanlai@gmail.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>


> On Mar 28, 2024, at 1:20=E2=80=AFPM, Lai Jiangshan <jiangshanlai@gmail.com=
> wrote:
>=20
> =EF=BB=BFFrom: Lai Jiangshan <jiangshan.ljs@antgroup.com>
>=20
> Prepare for arch-specific-defined rcu_preempt_depth_set().
>=20
> No functionality change intended, but it has to be defined as a macro
> as rcupdate.h is a very low level header included from areas that don't
> even know about the task struct "current".

Sorry I did not follow changelog. If some rcupdate.h includers do not know
about task_struct, how does adding a macro that uses current help?

Thanks,

 - Joel

>=20
> Cc: "Paul E. McKenney" <paulmck@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Frederic Weisbecker <frederic@kernel.org>
> Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
> ---
> include/linux/rcupdate.h | 1 +
> kernel/rcu/tree_plugin.h | 5 -----
> 2 files changed, 1 insertion(+), 5 deletions(-)
>=20
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 16f519914415..210f65baf47c 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -78,6 +78,7 @@ void __rcu_read_unlock(void);
>  * types of kernel builds, the rcu_read_lock() nesting depth is unknowable=
.
>  */
> #define rcu_preempt_depth() READ_ONCE(current->rcu_read_lock_nesting)
> +#define rcu_preempt_depth_set(val) WRITE_ONCE(current->rcu_read_lock_nest=
ing, (val))
>=20
> #else /* #ifdef CONFIG_PREEMPT_RCU */
>=20
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 36a8b5dbf5b5..b1264096d03a 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -387,11 +387,6 @@ static int rcu_preempt_read_exit(void)
>    return ret;
> }
>=20
> -static void rcu_preempt_depth_set(int val)
> -{
> -    WRITE_ONCE(current->rcu_read_lock_nesting, val);
> -}
> -
> /*
>  * Preemptible RCU implementation for rcu_read_lock().
>  * Just increment ->rcu_read_lock_nesting, shared state will be updated
> --
> 2.19.1.6.gb485710b
>=20