[tip:perf/core] perf evlist: Handle -EINVAL for sample_freq > max_sample_rate in strerror_open()

[tip-bot for Arnaldo Carvalho de Melo <tipbot@zytor.com>]

Commit-ID:  d9aade7fd27a604bbffd363e6a68416ef51bab88
Gitweb:     http://git.kernel.org/tip/d9aade7fd27a604bbffd363e6a68416ef51bab88
Author:     Arnaldo Carvalho de Melo <acme@redhat.com>
AuthorDate: Thu, 18 Feb 2016 13:34:09 -0300
Committer:  Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Fri, 19 Feb 2016 19:12:42 -0300

perf evlist: Handle -EINVAL for sample_freq > max_sample_rate in strerror_open()

When running the "code reading" test we get:

  # perf test -v "code reading" 2>&1 | tail -5
  Parsing event 'cycles:u'
  perf_evlist__open failed
  test child finished with -1
  ---- end ----
  Test object code reading: FAILED!
  #

And with -vv we get the errno value, -22, i.e. -EINVAL, but we can do
better and handle the case at hand, with this patch it becomes:

  # perf test -v "code reading" 2>&1 | tail -7
  perf_evlist__open() failed!
  Error: Invalid argument.
  Hint:  Check /proc/sys/kernel/perf_event_max_sample_rate.
  Hint:  The current value is 1000 and 4000 is being requested.
  test child finished with -1
  ---- end ----
  Test object code reading: FAILED!
  #

Next patch will make this 'perf test' entry to use perf_evlist__strerror()

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Steven Noonan <steven@uplinklabs.net>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-i31ai6kfefn75eapejjokfhc@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
 tools/perf/util/evlist.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index a7eb0ea..0f57716 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1624,7 +1624,7 @@ size_t perf_evlist__fprintf(struct perf_evlist *evlist, FILE *fp)
 	return printed + fprintf(fp, "\n");
 }
 
-int perf_evlist__strerror_open(struct perf_evlist *evlist __maybe_unused,
+int perf_evlist__strerror_open(struct perf_evlist *evlist,
 			       int err, char *buf, size_t size)
 {
 	int printed, value;
@@ -1652,7 +1652,25 @@ int perf_evlist__strerror_open(struct perf_evlist *evlist __maybe_unused,
 				    "Hint:\tTry: 'sudo sh -c \"echo -1 > /proc/sys/kernel/perf_event_paranoid\"'\n"
 				    "Hint:\tThe current value is %d.", value);
 		break;
+	case EINVAL: {
+		struct perf_evsel *first = perf_evlist__first(evlist);
+		int max_freq;
+
+		if (sysctl__read_int("kernel/perf_event_max_sample_rate", &max_freq) < 0)
+			goto out_default;
+
+		if (first->attr.sample_freq < (u64)max_freq)
+			goto out_default;
+
+		printed = scnprintf(buf, size,
+				    "Error:\t%s.\n"
+				    "Hint:\tCheck /proc/sys/kernel/perf_event_max_sample_rate.\n"
+				    "Hint:\tThe current value is %d and %" PRIu64 " is being requested.",
+				    emsg, max_freq, first->attr.sample_freq);
+		break;
+	}
 	default:
+out_default:
 		scnprintf(buf, size, "%s", emsg);
 		break;
 	}