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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: Mon, 1 Apr 2024 07:57:56 +0530
Message-Id: <B89CA77D-2E7C-4AE7-B4AA-06BF681A983A@joelfernandes.org>
References: <CAJhGHyDjoQ3TrApksYJ5o1ooU4s8rzys2UnfF6EFzGwkaSVaKA@mail.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: <CAJhGHyDjoQ3TrApksYJ5o1ooU4s8rzys2UnfF6EFzGwkaSVaKA@mail.gmail.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>


> On Mar 31, 2024, at 9:46=E2=80=AFPM, Lai Jiangshan <jiangshanlai@gmail.com=
> wrote:
>=20
> =EF=BB=BFOn Sun, Mar 31, 2024 at 7:10=E2=80=AFPM Joel Fernandes <joel@joel=
fernandes.org> wrote:
>>=20
>>=20
>>=20
>>>> 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".
>>=20
>> Sorry I did not follow changelog. If some rcupdate.h includers do not kno=
w
>> about task_struct, how does adding a macro that uses current help?
>>=20
>=20
> Hello
>=20
> This is how macro works and it expands blindly based on tokens on the
> usage-sites.
>=20
> And rcu_preempt_depth() & rcu_preempt_depth_set() are not universally
> used wrappers, the user can simply also include linux/sched.h to make
> they work.

Oh I see, so by hiding it in a macro, the code remains unexpanded. That make=
s sense..

Thanks.


>=20
> Thanks
> Lai