linux-kernel - Re: [PATCH V7 01/18] perf/core: Use static_call to optimize perf_guest_info

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Message-ID: <7379289718c6826dd1affec5824b749be2aee0a4.camel@perches.com>
Date:   Fri, 02 Jul 2021 09:00:22 -0700
From:   Joe Perches <joe@...ches.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Zhu Lingshan <lingshan.zhu@...el.com>
Cc:     pbonzini@...hat.com, bp@...en8.de, seanjc@...gle.com,
        vkuznets@...hat.com, wanpengli@...cent.com, jmattson@...gle.com,
        joro@...tes.org, weijiang.yang@...el.com,
        kan.liang@...ux.intel.com, ak@...ux.intel.com,
        wei.w.wang@...el.com, eranian@...gle.com, liuxiangdong5@...wei.com,
        linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
        like.xu.linux@...il.com, Like Xu <like.xu@...ux.intel.com>,
        Will Deacon <will@...nel.org>, Marc Zyngier <maz@...nel.org>,
        Guo Ren <guoren@...nel.org>, Nick Hu <nickhu@...estech.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-csky@...r.kernel.org, linux-riscv@...ts.infradead.org,
        xen-devel@...ts.xenproject.org
Subject: Re: [PATCH V7 01/18] perf/core: Use static_call to optimize
 perf_guest_info_callbacks

On Fri, 2021-07-02 at 13:22 +0200, Peter Zijlstra wrote:
> On Tue, Jun 22, 2021 at 05:42:49PM +0800, Zhu Lingshan wrote:
> > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
[]
> > @@ -90,6 +90,27 @@ DEFINE_STATIC_CALL_NULL(x86_pmu_pebs_aliases, *x86_pmu.pebs_aliases);
> >   */
> >  DEFINE_STATIC_CALL_RET0(x86_pmu_guest_get_msrs, *x86_pmu.guest_get_msrs);
> >  
> > 
> > +DEFINE_STATIC_CALL_RET0(x86_guest_state, *(perf_guest_cbs->state));
> > +DEFINE_STATIC_CALL_RET0(x86_guest_get_ip, *(perf_guest_cbs->get_ip));
> > +DEFINE_STATIC_CALL_RET0(x86_guest_handle_intel_pt_intr, *(perf_guest_cbs->handle_intel_pt_intr));
> > +
> > +void arch_perf_update_guest_cbs(void)
> > +{
> > +	static_call_update(x86_guest_state, (void *)&__static_call_return0);
> > +	static_call_update(x86_guest_get_ip, (void *)&__static_call_return0);
> > +	static_call_update(x86_guest_handle_intel_pt_intr, (void *)&__static_call_return0);
> > +
> > +	if (perf_guest_cbs && perf_guest_cbs->state)
> > +		static_call_update(x86_guest_state, perf_guest_cbs->state);
> > +
> > +	if (perf_guest_cbs && perf_guest_cbs->get_ip)
> > +		static_call_update(x86_guest_get_ip, perf_guest_cbs->get_ip);
> > +
> > +	if (perf_guest_cbs && perf_guest_cbs->handle_intel_pt_intr)
> > +		static_call_update(x86_guest_handle_intel_pt_intr,
> > +				   perf_guest_cbs->handle_intel_pt_intr);
> > +}
> 
> Coding style wants { } on that last if().

That's just your personal preference.

The coding-style document doesn't require that.

It just says single statement.  It's not the number of
vertical lines or characters required for the statement.

----------------------------------

Do not unnecessarily use braces where a single statement will do.

.. code-block:: c

	if (condition)
		action();

and

.. code-block:: none

	if (condition)
		do_this();
	else
		do_that();

This does not apply if only one branch of a conditional statement is a single
statement; in the latter case use braces in both branches: