[tip:perf/urgent] perf evlist: Fix side band thread draining

[tip-bot for Jiri Olsa]

Commit-ID:  adc6257c4a6f23ff97dca8314fcd33828e2d8db5
Gitweb:     https://git.kernel.org/tip/adc6257c4a6f23ff97dca8314fcd33828e2d8db5
Author:     Jiri Olsa <jolsa@xxxxxxxxxx>
AuthorDate: Tue, 16 Apr 2019 18:01:23 +0200
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Wed, 17 Apr 2019 14:30:11 -0300

perf evlist: Fix side band thread draining

Current perf_evlist__poll_thread() code could finish without draining
the data. Adding the logic that makes sure we won't finish before the
drain.

Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Alexei Starovoitov <ast@xxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Daniel Borkmann <daniel@xxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Song Liu <songliubraving@xxxxxx>
Fixes: 657ee5531903 ("perf evlist: Introduce side band thread")
Link: http://lkml.kernel.org/r/20190416160127.30203-9-jolsa@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/util/evlist.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index 6689378ee577..51ead577533f 100644
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -1868,12 +1868,12 @@ static void *perf_evlist__poll_thread(void *arg)
 {
 	struct perf_evlist *evlist = arg;
 	bool draining = false;
-	int i;
+	int i, done = 0;
+
+	while (!done) {
+		bool got_data = false;
 
-	while (draining || !(evlist->thread.done)) {
-		if (draining)
-			draining = false;
-		else if (evlist->thread.done)
+		if (evlist->thread.done)
 			draining = true;
 
 		if (!draining)
@@ -1894,9 +1894,13 @@ static void *perf_evlist__poll_thread(void *arg)
 					pr_warning("cannot locate proper evsel for the side band event\n");
 
 				perf_mmap__consume(map);
+				got_data = true;
 			}
 			perf_mmap__read_done(map);
 		}
+
+		if (draining && !got_data)
+			break;
 	}
 	return NULL;
 }