linux-kernel - Re: [PATCH 09/10] x86/rcu: Add rcu_preempt

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Message-ID: <ZiecmBdOwHaaMufg@localhost.localdomain>
Date: Tue, 23 Apr 2024 13:33:44 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Lai Jiangshan <jiangshanlai@...il.com>
Cc: linux-kernel@...r.kernel.org, rcu@...r.kernel.org, x86@...nel.org,
	Lai Jiangshan <jiangshan.ljs@...group.com>,
	"Paul E. McKenney" <paulmck@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>, Uros Bizjak <ubizjak@...il.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>, Nadav Amit <namit@...are.com>,
	Breno Leitao <leitao@...ian.org>,
	Kent Overstreet <kent.overstreet@...ux.dev>,
	Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
	Rick Edgecombe <rick.p.edgecombe@...el.com>,
	Vegard Nossum <vegard.nossum@...cle.com>,
	Daniel Sneddon <daniel.sneddon@...ux.intel.com>,
	Nikolay Borisov <nik.borisov@...e.com>
Subject: Re: [PATCH 09/10] x86/rcu: Add rcu_preempt_count

Le Tue, Apr 23, 2024 at 05:02:35PM +0800, Lai Jiangshan a écrit :
> Hello, Frederic
> 
> Thanks for reviewing.
> 
> On Mon, Apr 22, 2024 at 7:05 PM Frederic Weisbecker <frederic@...nel.org> wrote:
> 
> > > +
> > > +/* We use the MSB mostly because its available */
> >
> > I think you can safely remove the "We " from all the comments :-)
> 
> The file is mainly copied from arch/x86/include/asm/preempt.h.
> I will rephrase sentences in later iterations.
> 
> >
> > > +#define RCU_PREEMPT_UNLOCK_SPECIAL_INVERTED  0x80000000
> >
> > How about RCU_PREEMPT_UNLOCK_FASTPATH ?
> 
> 
> I'm not good at naming. But the MSB really means exactly the opposite
> of current->rcu_read_unlock_special and I think "UNLOCK_SPECIAL_INVERTED"
> fits the meaning.

Right but I tend to think a constant should tell what something is, not what
something is not.

FWIW, p->rcu_read_unlock_special could even be renamed to p->rcu_read_unlock_slowpath

Thanks.