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From:   Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Date:   Fri, 26 Apr 2019 11:16:07 -0300
To:     Thomas Richter <tmricht@linux.ibm.com>
Cc:     linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org,
        brueckner@linux.vnet.ibm.com, schwidefsky@de.ibm.com,
        heiko.carstens@de.ibm.com, jolsa@redhat.com
Subject: Re: [PATCH] perf/report: Report OOM in perf report status line
Message-ID: <20190426141607.GB23426@kernel.org>
References: <20190423105303.61683-1-tmricht@linux.ibm.com>
 <20190426140907.GB22086@kernel.org>
 <20190426141032.GA23426@kernel.org>
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Em Fri, Apr 26, 2019 at 11:10:32AM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Fri, Apr 26, 2019 at 11:09:07AM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Tue, Apr 23, 2019 at 12:53:03PM +0200, Thomas Richter escreveu:
> > > An -ENOMEM error is not reported in the GTK GUI.
> > > Instead this error message pops up on the screen:
> > > 
> > > [root@m35lp76 perf]# ./perf  report -i perf.data.error68-1
> > > 
> > > 	Processing events... [974K/3M]
> > > 	Error:failed to process sample
> > > 
> > > 	0xf4198 [0x8]: failed to process type: 68
> > 
> > Thanks, applied to perf/urgent.
> 
> Well, I tried to, now trying to fix this...
> 
> 
> [acme@quaco perf]$ m
> make: Entering directory '/home/acme/git/perf/tools/perf'
>   BUILD:   Doing 'make -j8' parallel build
>   INSTALL  GTK UI
>   INSTALL  trace_plugins
>   CC       /tmp/build/perf/util/session.o
> util/session.c: In function ‘perf_session__process_events’:
> util/session.c:1936:7: error: ‘skip’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
>    err = skip;
>    ~~~~^~~~~~
> util/session.c:1874:6: note: ‘skip’ was declared here
>   s64 skip;
>       ^~~~
> cc1: all warnings being treated as errors
> mv: cannot stat '/tmp/build/perf/util/.session.o.tmp': No such file or directory
> make[4]: *** [/home/acme/git/perf/tools/build/Makefile.build:96: /tmp/build/perf/util/session.o] Error 1
> make[3]: *** [/home/acme/git/perf/tools/build/Makefile.build:139: util] Error 2
> make[2]: *** [Makefile.perf:559: /tmp/build/perf/perf-in.o] Error 2
> make[1]: *** [Makefile.perf:215: sub-make] Error 2
> make: *** [Makefile:110: install-bin] Error 2
> make: Leaving directory '/home/acme/git/perf/tools/perf'

So, here is your patch:

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index b17f1c9bc965..e89716175588 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1930,10 +1930,10 @@ reader__process_events(struct reader *rd, struct perf_session *session,

        if (size < sizeof(struct perf_event_header) ||
            (skip = rd->process(session, event, file_pos)) < 0) {
-               pr_err("%#" PRIx64 " [%#x]: failed to process type: %d\n",
+               pr_err("%#" PRIx64 " [%#x]: failed to process type: %d [%s]\n",
                       file_offset + head, event->header.size,
-                      event->header.type);
-               err = -EINVAL;
+                      event->header.type, strerror(-skip));
+               err = skip;
                goto out;
        }

[acme@quaco perf]$

What happens if (size < sizeof(struct perf_event_header)) is true? size
will have an undefined value, so the right thing is to have this patch
on top of yours, so that err get, as before, set to -EINVAL when the
size is less than the perf_event_header sizeof:

diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index e89716175588..bad5f87ae001 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -1928,6 +1928,8 @@ reader__process_events(struct reader *rd, struct perf_session *session,
 
 	size = event->header.size;
 
+	skip = -EINVAL;
+
 	if (size < sizeof(struct perf_event_header) ||
 	    (skip = rd->process(session, event, file_pos)) < 0) {
 		pr_err("%#" PRIx64 " [%#x]: failed to process type: %d [%s]\n",

---

With two Reviewed-by tags, I jumped to quickly at applying, please
compile test next time guys ;-) :-)

- Arnaldo