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Subject: Re: [PATCH 02/10] rcu: Move rcu_preempt_depth_set() to rcupdate.h
From: Alan Huang <mmpgouride@gmail.com>
In-Reply-To: <073E72BD-63AF-4D88-95F8-9A002252C554@gmail.com>
Date: Mon, 1 Apr 2024 19:57:40 +0800
Cc: Joel Fernandes <joel@joelfernandes.org>,
 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>
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Message-Id: <60BB1971-38D3-4FE2-BB45-2DE228C6F370@gmail.com>
References: <20240328075318.83039-3-jiangshanlai@gmail.com>
 <769AEAAB-7DEA-4D94-8979-F01EDFD6EE46@joelfernandes.org>
 <CAJhGHyDjoQ3TrApksYJ5o1ooU4s8rzys2UnfF6EFzGwkaSVaKA@mail.gmail.com>
 <073E72BD-63AF-4D88-95F8-9A002252C554@gmail.com>
To: Lai Jiangshan <jiangshanlai@gmail.com>

2024=E5=B9=B44=E6=9C=881=E6=97=A5 19:40=EF=BC=8CAlan Huang =
<mmpgouride@gmail.com> wrote=EF=BC=9A
>=20
> 2024=E5=B9=B44=E6=9C=881=E6=97=A5 00:16=EF=BC=8CLai Jiangshan =
<jiangshanlai@gmail.com> wrote=EF=BC=9A
>>=20
>> On Sun, Mar 31, 2024 at 7:10=E2=80=AFPM Joel Fernandes =
<joel@joelfernandes.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 know
>>> 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
> But =E2=80=98current=E2=80=99 still needs to be expanded at last, it =
seems to me that it only affects=20
> the including order of the header files=EF=BC=9F
>=20
> Or what am I missing?

Get the missing part: if the user don=E2=80=99t need to use =
rcu_preempt_depth()=20
and rcu_preempt_depth_set() but other parts of rcupdate.h, then the two
has to be defined as a macro to avoid including linux/sched.h.

Sorry for the bother.

>=20
>>=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.
>>=20
>> Thanks
>> Lai