Re: [PATCH] perf/x86/intel: Mark expected switch fall-throughs

Peter Zijlstra
2019-06-24T20:38:13Z

On Mon, Jun 24, 2019 at 12:45:54PM -0700, Joe Perches wrote:
> On Mon, 2019-06-24 at 21:31 +0200, Peter Zijlstra wrote:
> > On Mon, Jun 24, 2019 at 11:19:13AM -0500, Gustavo A. R. Silva wrote:
> > > In preparation to enabling -Wimplicit-fallthrough, mark switch
> > > cases where we are expecting to fall through.
> > >
> > > This patch fixes the following warnings:
> > >
> > > arch/x86/events/intel/core.c: In function ‘intel_pmu_init’:
> > > arch/x86/events/intel/core.c:4959:8: warning: this statement may fall through [-Wimplicit-fallthrough=]
> > > pmem = true;
> > > ~~~~~^~~~~~
> > > arch/x86/events/intel/core.c:4960:2: note: here
> > > case INTEL_FAM6_SKYLAKE_MOBILE:
> > > ^~~~
> > > arch/x86/events/intel/core.c:5008:8: warning: this statement may fall through [-Wimplicit-fallthrough=]
> > > pmem = true;
> > > ~~~~~^~~~~~
> > > arch/x86/events/intel/core.c:5009:2: note: here
> > > case INTEL_FAM6_ICELAKE_MOBILE:
> > > ^~~~
> > >
> > > Warning level 3 was used: -Wimplicit-fallthrough=3
> > >
> > > This patch is part of the ongoing efforts to enable
> > > -Wimplicit-fallthrough.
> > >
> > > Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
> >
> > I still consider it an abomination that the C parser looks at comments
> > -- other than to delete them, but OK I suppose, I'll take it.
>
> I still believe Arnaldo's/Miguel's/Shawn's/my et al. suggestion of
>
> #define __fallthrough __attribute__((fallthrough))
>
> is far better.
>
> https://lkml.org/lkml/2017/2/9/845
> https://lkml.org/lkml/2017/2/10/485
> https://lore.kernel.org/lkml/20181021171414.22674-2-miguel.ojeda.sandonis@gmail.com/
> https://lore.kernel.org/lkml/20190617155643.GA32544@amd/

Oh yes, worlds better. Please, can we haz that instead?