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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20210702163836.GB94260@C02TD0UTHF1T.local>
Date:   Fri, 2 Jul 2021 17:38:36 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Joe Perches <joe@...ches.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Zhu Lingshan <lingshan.zhu@...el.com>, wanpengli@...cent.com,
        Like Xu <like.xu@...ux.intel.com>, eranian@...gle.com,
        weijiang.yang@...el.com, Guo Ren <guoren@...nel.org>,
        linux-riscv@...ts.infradead.org, Will Deacon <will@...nel.org>,
        kvmarm@...ts.cs.columbia.edu, kan.liang@...ux.intel.com,
        ak@...ux.intel.com, kvm@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>, joro@...tes.org, x86@...nel.org,
        linux-csky@...r.kernel.org, wei.w.wang@...el.com,
        xen-devel@...ts.xenproject.org, liuxiangdong5@...wei.com,
        bp@...en8.de, Paul Walmsley <paul.walmsley@...ive.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        linux-arm-kernel@...ts.infradead.org, jmattson@...gle.com,
        like.xu.linux@...il.com, Nick Hu <nickhu@...estech.com>,
        seanjc@...gle.com, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, vkuznets@...hat.com
Subject: Re: [PATCH V7 01/18] perf/core: Use static_call to optimize
 perf_guest_info_callbacks

On Fri, Jul 02, 2021 at 09:00:22AM -0700, Joe Perches wrote:
> 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:

Immediately after this, we say:

| Also, use braces when a loop contains more than a single simple statement:
|
| .. code-block:: c
| 
|         while (condition) {
|                 if (test)
|                         do_something();
|         }
| 

... and while that says "a loop", the principle is obviously supposed to
apply to conditionals too; structurally they're no different. We should
just fix the documentation to say "a loop or conditional", or something
to that effect.

Mark.