Re: [PATCH V7 01/18] perf/core: Use static_call to optimize perf_guest_info_callbacks

Joe Perches
2021-07-02T16:08:11Z

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: