linux-kernel - Re: [RFC PATCH] compiler.h: Introduce ptr

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Message-ID: <55678fb6-4476-4e25-82d5-5d5ad5b7e7d9@paulmck-laptop>
Date: Sat, 28 Sep 2024 04:32:06 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Boqun Feng <boqun.feng@...il.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Will Deacon <will@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Alan Stern <stern@...land.harvard.edu>,
	John Stultz <jstultz@...gle.com>,
	Neeraj Upadhyay <Neeraj.Upadhyay@....com>,
	Frederic Weisbecker <frederic@...nel.org>,
	Joel Fernandes <joel@...lfernandes.org>,
	Josh Triplett <josh@...htriplett.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Lai Jiangshan <jiangshanlai@...il.com>,
	Zqiang <qiang.zhang1211@...il.com>, Ingo Molnar <mingo@...hat.com>,
	Waiman Long <longman@...hat.com>,
	Mark Rutland <mark.rutland@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Vlastimil Babka <vbabka@...e.cz>, maged.michael@...il.com,
	Mateusz Guzik <mjguzik@...il.com>, rcu@...r.kernel.org,
	linux-mm@...ck.org, lkmm@...ts.linux.dev
Subject: Re: [RFC PATCH] compiler.h: Introduce ptr_eq() to preserve address
 dependency

On Fri, Sep 27, 2024 at 07:05:53PM -0400, Mathieu Desnoyers wrote:
> On 2024-09-27 22:33, Mathieu Desnoyers wrote:
> [...]
> 
> > ---
> >   include/linux/compiler.h | 62 ++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 62 insertions(+)
> > 
> 
> I'm wondering if this really belongs in compiler.h, or if it's so
> RCU/HP specific that it should be implemented in rcupdate.h ?
> 
> [... ]
> > +static __always_inline
> > +int ptr_eq(const volatile void *a, const volatile void *b)
> 
> And perhaps rename this to rcu_ptr_eq() ?

For either location or name:

Acked-by: Paul E. McKenney <paulmck@...nel.org>

There are non-RCU uses, but RCU is currently by far the most common.

							Thanx, Paul

> Thanks,
> 
> Mathieu
> 
> > +{
> > +	OPTIMIZER_HIDE_VAR(a);
> > +	OPTIMIZER_HIDE_VAR(b);
> > +	return a == b;
> > +}
> > +
> 
> 
> 
> -- 
> Mathieu Desnoyers
> EfficiOS Inc.
> https://www.efficios.com
>