linux-kernel - Re: [PATCH 14/19] rcu/context-tracking: Move RCU-dynticks internal functions to context

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Message-ID: <20220312231048.GI28057@worktop.programming.kicks-ass.net>
Date:   Sun, 13 Mar 2022 00:10:48 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>, Phil Auld <pauld@...hat.com>,
        Alex Belits <abelits@...vell.com>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        Neeraj Upadhyay <quic_neeraju@...cinc.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Yu Liao <liaoyu15@...wei.com>,
        Boqun Feng <boqun.feng@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>,
        Uladzislau Rezki <uladzislau.rezki@...y.com>,
        Joel Fernandes <joel@...lfernandes.org>
Subject: Re: [PATCH 14/19] rcu/context-tracking: Move RCU-dynticks internal
 functions to context_tracking

On Wed, Mar 02, 2022 at 04:48:05PM +0100, Frederic Weisbecker wrote:
> +noinstr unsigned long rcu_dynticks_inc(int incby)
> +{
> +	return arch_atomic_add_return(incby, this_cpu_ptr(&context_tracking.dynticks));
> +}

noinstr implies noinline, making the above a rather sad little function;
would it perhaps be better to make it __always_inline ?

Also; I could imagine myself doing an arch special for this such that
x86 generates:

	LOCK XADD	[reg], %gs:[var]

But that's for later I suppose, it would be but a little tweak to
perpcu_add_return_op()