perf evlist: Drop redundant evsel->overwrite indicator

evsel->overwrite indicator means an event should be put into
overwritable ring buffer. In current implementation, it equals to
evsel->attr.write_backward. To reduce compliexity, remove
evsel->overwrite, use evsel->attr.write_backward instead.

In addition, in __perf_evsel__open(), if kernel doesn't support
write_backward and user explicitly set it in evsel, don't fallback
like other missing feature, since it is meaningless to fall back to
a forward ring buffer in this case: we are unable to stably read
from an forward overwritable ring buffer.

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: Nilay Vaish <nilayvaish@gmail.com>
Cc: Wang Nan <wangnan0@huawei.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1468485287-33422-2-git-send-email-wangnan0@huawei.com
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 8 insertions, 10 deletions

diff --git a/tools/perf/tests/backward-ring-buffer.c b/tools/perf/tests/backward-ring-buffer.c
index f20ea4c0d0cb..5cee3873f2b5 100644
--- a/tools/perf/tests/backward-ring-buffer.c
+++ b/tools/perf/tests/backward-ring-buffer.c
@@ -101,6 +101,7 @@ int test__backward_ring_buffer(int subtest __maybe_unused)
                 return TEST_FAIL;
         }
 
+        evlist->backward = true;
         err = perf_evlist__create_maps(evlist, &opts.target);
         if (err < 0) {
                 pr_debug("Not enough memory to create thread/cpu maps\n");
diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 862e69c2690d..6803f5ccd15e 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1003,7 +1003,7 @@ static bool
 perf_evlist__should_poll(struct perf_evlist *evlist __maybe_unused,
                          struct perf_evsel *evsel)
 {
-        if (evsel->overwrite)
+        if (evsel->attr.write_backward)
                 return false;
         return true;
 }
@@ -1018,7 +1018,7 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx,
         evlist__for_each_entry(evlist, evsel) {
                 int fd;
 
-                if (evsel->overwrite != (evlist->overwrite && evlist->backward))
+                if (!!evsel->attr.write_backward != (evlist->overwrite && evlist->backward))
                         continue;
 
                 if (evsel->system_wide && thread)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index ba0f59fa3d5d..9ac2f92ce88d 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -1377,6 +1377,9 @@ static int __perf_evsel__open(struct perf_evsel *evsel, struct cpu_map *cpus,
         int pid = -1, err;
         enum { NO_CHANGE, SET_TO_MAX, INCREASED_MAX } set_rlimit = NO_CHANGE;
 
+        if (perf_missing_features.write_backward && evsel->attr.write_backward)
+                return -EINVAL;
+
         if (evsel->system_wide)
                 nthreads = 1;
         else
@@ -1407,11 +1410,6 @@ 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 (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;
@@ -1513,7 +1511,7 @@ try_fallback:
          */
         if (!perf_missing_features.write_backward && evsel->attr.write_backward) {
                 perf_missing_features.write_backward = true;
-                goto fallback_missing_features;
+                goto out_close;
         } else if (!perf_missing_features.clockid_wrong && evsel->attr.use_clockid) {
                 perf_missing_features.clockid_wrong = true;
                 goto fallback_missing_features;
@@ -2422,7 +2420,7 @@ 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)
+                if (evsel->attr.write_backward && 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.");
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index d73391e8740e..e60cbfc2cd35 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -114,7 +114,6 @@ struct perf_evsel {
         bool                    tracking;
         bool                    per_pkg;
         bool                    precise_max;
-        bool                    overwrite;
         /* parse modifier helper */
         int                     exclude_GH;
         int                     nr_members;