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>

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index a7eb0ea..0f57716 100644 (file)
--- 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;
        }