From 7da36e94e7fad768ca8640b61ed1f49b284e1dc5 Mon Sep 17 00:00:00 2001 From: Arnaldo Carvalho de Melo Date: Mon, 20 Jun 2016 10:47:18 +0000 Subject: [PATCH] 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 Cc: Jiri Olsa Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Zefan Li 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 Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/evsel.c | 23 ++++++++++------------- 1 file changed, 10 insertions(+), 13 deletions(-) diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 9b2e3e624efe..1d8f2bbd38a7 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -1389,8 +1389,11 @@ fallback_missing_features: 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 @@ retry_open: err = -EINVAL; goto out_close; } - - if (evsel->overwrite && - perf_missing_features.write_backward) { - err = -EINVAL; - goto out_close; - } } } @@ -1496,7 +1493,10 @@ try_fallback: * 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 @@ try_fallback: 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 @@ int perf_evsel__open_strerror(struct perf_evsel *evsel, struct target *target, "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) -- 2.20.1