linux-kernel - Re: [PATCH] perf/x86/intel: Fix unwind errors from PEBS entries (mk-II)

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Date:   Mon, 6 Aug 2018 14:28:18 -0700
From:   Fubo Chen <fubo.chen@...il.com>
To:     peterz@...radead.org
Cc:     jpoimboe@...hat.com, Ingo Molnar <mingo@...nel.org>,
        bhole_prashant_q7@....ntt.co.jp,
        Linux Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf/x86/intel: Fix unwind errors from PEBS entries (mk-II)

On Mon, Aug 6, 2018 at 11:04 AM Peter Zijlstra <peterz@...radead.org> wrote:
> On Mon, Aug 06, 2018 at 09:54:23AM -0700, Fubo Chen wrote:
> > On Mon, Aug 6, 2018 at 8:42 AM Peter Zijlstra <peterz@...radead.org> wrote:
> > > On Mon, Aug 06, 2018 at 08:35:07AM -0700, Fubo Chen wrote:
> > > > On Thu, Jul 19, 2018 at 2:21 PM Peter Zijlstra <peterz@...radead.org> wrote:
> > > > > --- a/include/uapi/linux/perf_event.h
> > > > > +++ b/include/uapi/linux/perf_event.h
> > > > > @@ -143,6 +143,8 @@ enum perf_event_sample_format {
> > > > >         PERF_SAMPLE_PHYS_ADDR                   = 1U << 19,
> > > > >
> > > > >         PERF_SAMPLE_MAX = 1U << 20,             /* non-ABI */
> > > > > +
> > > > > +       __PERF_SAMPLE_CALLCHAIN_EARLY           = 1UL << 63,
> > > > >  };
> > > >
> > > > The above change makes sparse unhappy :-( Sparse reports the following
> > > > complaint about __PERF_SAMPLE_CALLCHAIN_EARLY:
> > >
> > > I thought I changed that to 1ULL before commit.
> >
> > The sparse complaint was reported for code with the "1ULL << 63".
>
> Ah ok.. and I think I see what you mean. The C standard says that enums
> shall be 'int'. However C++ standard says any integer type that fits the
> largest value.
>
> I suppose GCC uses the C++ definition and I suspect many other compilers
> will too.

Do you think the patch below is sufficient to suppress the sparse warning?

---
 include/uapi/linux/perf_event.h       | 2 +-
 tools/include/uapi/linux/perf_event.h | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index eeb787b1c53c..0f0f43599b74 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -144,8 +144,8 @@ enum perf_event_sample_format {

  PERF_SAMPLE_MAX = 1U << 20, /* non-ABI */

- __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63,
 };
+#define __PERF_SAMPLE_CALLCHAIN_EARLY (1ULL << 63)

 /*
  * values to program into branch_sample_type when PERF_SAMPLE_BRANCH is set
diff --git a/tools/include/uapi/linux/perf_event.h
b/tools/include/uapi/linux/perf_event.h
index eeb787b1c53c..3db800bc8d2e 100644
--- a/tools/include/uapi/linux/perf_event.h
+++ b/tools/include/uapi/linux/perf_event.h
@@ -143,9 +143,8 @@ enum perf_event_sample_format {
  PERF_SAMPLE_PHYS_ADDR = 1U << 19,

  PERF_SAMPLE_MAX = 1U << 20, /* non-ABI */
-
- __PERF_SAMPLE_CALLCHAIN_EARLY = 1ULL << 63,
 };
+#define __PERF_SAMPLE_CALLCHAIN_EARLY (1ULL << 63)

 /*
  * values to program into branch_sample_type when PERF_SAMPLE_BRANCH is set





-- 
Fubo.