perf evsel: Fix write_backwards fallback
Commit b90dc17a5d14 "perf evsel: Add overwrite attribute and check
write_backward" misunderstood the 'order' should be obeyed in
__perf_evsel__open.
But the way this was done for attr.write_backwards was buggy, as we need
to check features in the inverse order of their introduction to the
kernel, so that a newer tool checks first the newest perf_event_attr
fields, detecting that the older kernel doesn't have support for them.
Also, we can avoid calling sys_perf_event_open() if we have already
detected the missing of write_backward.
Cc: He Kuang <hekuang@huawei.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Fixes: b90dc17a5d14 ("perf evsel: Add overwrite attribute and check write_backward")
Link: http://lkml.kernel.org/r/1466419645-75551-2-git-send-email-wangnan0@huawei.com
Link: http://lkml.kernel.org/r/20160616214724.GI13337@kernel.org
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 9b2e3e6..1d8f2bb 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1389,8 +1389,11 @@
if (perf_missing_features.lbr_flags)
evsel->attr.branch_sample_type &= ~(PERF_SAMPLE_BRANCH_NO_FLAGS |
PERF_SAMPLE_BRANCH_NO_CYCLES);
- if (perf_missing_features.write_backward)
+ if (perf_missing_features.write_backward) {
+ if (evsel->overwrite)
+ return -EINVAL;
evsel->attr.write_backward = false;
+ }
retry_sample_id:
if (perf_missing_features.sample_id_all)
evsel->attr.sample_id_all = 0;
@@ -1453,12 +1456,6 @@
err = -EINVAL;
goto out_close;
}
-
- if (evsel->overwrite &&
- perf_missing_features.write_backward) {
- err = -EINVAL;
- goto out_close;
- }
}
}
@@ -1496,7 +1493,10 @@
* Must probe features in the order they were added to the
* perf_event_attr interface.
*/
- if (!perf_missing_features.clockid_wrong && evsel->attr.use_clockid) {
+ if (!perf_missing_features.write_backward && evsel->attr.write_backward) {
+ perf_missing_features.write_backward = true;
+ goto fallback_missing_features;
+ } else if (!perf_missing_features.clockid_wrong && evsel->attr.use_clockid) {
perf_missing_features.clockid_wrong = true;
goto fallback_missing_features;
} else if (!perf_missing_features.clockid && evsel->attr.use_clockid) {
@@ -1521,12 +1521,7 @@
PERF_SAMPLE_BRANCH_NO_FLAGS))) {
perf_missing_features.lbr_flags = true;
goto fallback_missing_features;
- } else if (!perf_missing_features.write_backward &&
- evsel->attr.write_backward) {
- perf_missing_features.write_backward = true;
- goto fallback_missing_features;
}
-
out_close:
do {
while (--thread >= 0) {
@@ -2409,6 +2404,8 @@
"We found oprofile daemon running, please stop it and try again.");
break;
case EINVAL:
+ if (evsel->overwrite && perf_missing_features.write_backward)
+ return scnprintf(msg, size, "Reading from overwrite event is not supported by this kernel.");
if (perf_missing_features.clockid)
return scnprintf(msg, size, "clockid feature not supported.");
if (perf_missing_features.clockid_wrong)