perf record: Read from overwritable ring buffer

Drive the evlist->bkw_mmap_state state machine during draining and when
SIGUSR2 is received. Read the backward ring buffer in record__mmap_read_all.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Zefan Li <lizefan@huawei.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1468485287-33422-12-git-send-email-wangnan0@huawei.com
Signed-off-by: He Kuang <hekuang@huawei.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 30 insertions, 1 deletions

diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c
index d4f15e76c98a..b87070b1f492 100644
--- a/tools/perf/builtin-record.c
+++ b/tools/perf/builtin-record.c
@@ -555,7 +555,7 @@ static int record__mmap_read_all(struct record *rec)
         if (err)
                 return err;
 
-        return err;
+        return record__mmap_read_evlist(rec, rec->evlist, true);
 }
 
 static void record__init_features(struct record *rec)
@@ -953,6 +953,17 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
         for (;;) {
                 unsigned long long hits = rec->samples;
 
+                /*
+                 * rec->evlist->bkw_mmap_state is possible to be
+                 * BKW_MMAP_EMPTY here: when done == true and
+                 * hits != rec->samples in previous round.
+                 *
+                 * perf_evlist__toggle_bkw_mmap ensure we never
+                 * convert BKW_MMAP_EMPTY to BKW_MMAP_DATA_PENDING.
+                 */
+                if (trigger_is_hit(&switch_output_trigger) || done || draining)
+                        perf_evlist__toggle_bkw_mmap(rec->evlist, BKW_MMAP_DATA_PENDING);
+
                 if (record__mmap_read_all(rec) < 0) {
                         trigger_error(&auxtrace_snapshot_trigger);
                         trigger_error(&switch_output_trigger);
@@ -972,8 +983,26 @@ static int __cmd_record(struct record *rec, int argc, const char **argv)
                 }
 
                 if (trigger_is_hit(&switch_output_trigger)) {
+                        /*
+                         * If switch_output_trigger is hit, the data in
+                         * overwritable ring buffer should have been collected,
+                         * so bkw_mmap_state should be set to BKW_MMAP_EMPTY.
+                         *
+                         * If SIGUSR2 raise after or during record__mmap_read_all(),
+                         * record__mmap_read_all() didn't collect data from
+                         * overwritable ring buffer. Read again.
+                         */
+                        if (rec->evlist->bkw_mmap_state == BKW_MMAP_RUNNING)
+                                continue;
                         trigger_ready(&switch_output_trigger);
 
+                        /*
+                         * Reenable events in overwrite ring buffer after
+                         * record__mmap_read_all(): we should have collected
+                         * data from it.
+                         */
+                        perf_evlist__toggle_bkw_mmap(rec->evlist, BKW_MMAP_RUNNING);
+
                         if (!quiet)
                                 fprintf(stderr, "[ perf record: dump data: Woken up %ld times ]\n",
                                         waking);