linux-kernel - Re: [PATCH] perf jevents: Fix sys_event_tables to be freed like arch_std

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Date:   Tue, 28 Sep 2021 14:56:30 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     John Garry <john.garry@...wei.com>
Cc:     Like Xu <like.xu.linux@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf jevents: Fix sys_event_tables to be freed like
 arch_std_events

Em Tue, Sep 28, 2021 at 02:32:02PM +0100, John Garry escreveu:
> On 28/09/2021 14:22, Arnaldo Carvalho de Melo wrote:
> >   jevents-y      += json.o jsmn.o jevents.o
> > -HOSTCFLAGS_jevents.o   = -I$(srctree)/tools/include
> > +HOSTCFLAGS_jevents.o   = -I$(srctree)/tools/include -Wall -Wextra
> >   pmu-events-y   += pmu-events.o
> >   JDIR           =  pmu-events/arch/$(SRCARCH)
> >   JSON           =  $(shell [ -d $(JDIR) ] &&                            \
> > ⬢[acme@...lbox perf]$
> > 
> > I get this before applying Xu's patch:
> > 
> >    LINK    /tmp/build/perf/libbpf.a
> > pmu-events/jevents.c: In function ‘save_arch_std_events’:
> > pmu-events/jevents.c:473:39: warning: unused parameter ‘data’ [-Wunused-parameter]
> >    473 | static int save_arch_std_events(void *data, struct json_event *je)
> >        |                                 ~~~~~~^~~~
> > At top level:
> > pmu-events/jevents.c:93:13: warning: ‘free_sys_event_tables’ defined but not used [-Wunused-function]
> >     93 | static void free_sys_event_tables(void)
> >        |             ^~~~~~~~~~~~~~~~~~~~~
> > 
> > 
> > -------------------------------------
> > 
> > I'll add this to perf/core, as this isn't a strict fix, so can wait for
> > v5.16.
> 
> Hi Arnaldo,
> 
> OK, would you also consider reusing CFLAGS:
> 
> --- a/tools/perf/pmu-events/Build
> +++ b/tools/perf/pmu-events/Build
> @@ -9,10 +9,12 @@ JSON          =  $(shell [ -d $(JDIR) ] &&
> \
> JDIR_TEST      =  pmu-events/arch/test
> JSON_TEST      =  $(shell [ -d $(JDIR_TEST) ] &&                       \
>                        find $(JDIR_TEST) -name '*.json')
> -
> +HOSTCFLAGS_jevents += $(CFLAGS)

Humm, we have to check if CFLAGS doesn't come with cross-build options,
i.e. IIRC we have to use HOSTCFLAGS instead. Unsure if there is some
*CFLAGS variable that gets the common part, where these -Wall and
-Wextra, -Werror could go.
 
> I tried it, and there are more things to fix for jevents.o. Let me know your
> preference and if any help required to fix any errors up.

I fixed the one I found, see below, I'll test build what I have in
perf/core and push it, then you can continue from there, after checking
this HOSTCFLAGS/CFLAGS issue.

- Arnaldo

>From 0e46c8307574a8e2dac8d7ba97e0f6f4bbee67a5 Mon Sep 17 00:00:00 2001
From: Arnaldo Carvalho de Melo <acme@...hat.com>
Date: Tue, 28 Sep 2021 14:15:01 -0300
Subject: [PATCH 1/1] perf jevents: Add __maybe_unused attribute to unused
 function arg

The tools/perf/pmu-events/jevents.c file isn't being compiled with
-Werror and -Wextra, which will be the case soon, so before we turn
those compiler flags on, fix what it would flag.

Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Like Xu <like.xu.linux@...il.com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
To: John Garry <john.garry@...wei.com>
---
 tools/perf/pmu-events/jevents.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/tools/perf/pmu-events/jevents.c b/tools/perf/pmu-events/jevents.c
index 6731b3cf0c2fc9b7..323e1dfe2436c049 100644
--- a/tools/perf/pmu-events/jevents.c
+++ b/tools/perf/pmu-events/jevents.c
@@ -45,6 +45,7 @@
 #include <sys/resource.h>		/* getrlimit */
 #include <ftw.h>
 #include <sys/stat.h>
+#include <linux/compiler.h>
 #include <linux/list.h>
 #include "jsmn.h"
 #include "json.h"
@@ -470,7 +471,7 @@ static void free_arch_std_events(void)
 	}
 }
 
-static int save_arch_std_events(void *data, struct json_event *je)
+static int save_arch_std_events(void *data __maybe_unused, struct json_event *je)
 {
 	struct event_struct *es;
 
-- 
2.31.1