[PATCH 2/3] perf tools: Do not rely on dso__data_read_offset() to open dso

[Namhyung Kim]

Do not rely on dso__data_read_offset() will always call dso__data_fd()
internally.  With multi-thread support, accessing a fd will be
protected by a lock and it'll cause a huge contention.  It can be
avoided since we can skip reading from file if there's a data in the
dso cache.

If one needs to call the dso__data_read_offset(), [s]he also needs to
call dso__data_fd() (or set dso->binary_type at least) first like the
dwarf unwind code does.

Signed-off-by: Namhyung Kim <namhyung@xxxxxxxxxx>
---
 tools/perf/tests/dso-data.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/tools/perf/tests/dso-data.c b/tools/perf/tests/dso-data.c
index 22a8c428283a..513e5febbe5a 100644
--- a/tools/perf/tests/dso-data.c
+++ b/tools/perf/tests/dso-data.c
@@ -112,6 +112,9 @@ int test__dso_data(void)
 
 	dso = dso__new((const char *)file);
 
+	TEST_ASSERT_VAL("Failed to access to dso",
+			dso__data_fd(dso, &machine) >= 0);
+
 	/* Basic 10 bytes tests. */
 	for (i = 0; i < ARRAY_SIZE(offsets); i++) {
 		struct test_data_offset *data = &offsets[i];
@@ -252,13 +255,13 @@ int test__dso_data_cache(void)
 		struct dso *dso = dsos[i];
 
 		/*
-		 * Open dsos via dso__data_fd or dso__data_read_offset.
-		 * Both opens the data file and keep it open.
+		 * Open dsos via dso__data_fd(), it opens the data
+		 * file and keep it open (unless open file limit).
 		 */
+		fd = dso__data_fd(dso, &machine);
+		TEST_ASSERT_VAL("failed to get fd", fd > 0);
+
 		if (i % 2) {
-			fd = dso__data_fd(dso, &machine);
-			TEST_ASSERT_VAL("failed to get fd", fd > 0);
-		} else {
 			#define BUFSIZE 10
 			u8 buf[BUFSIZE];
 			ssize_t n;
-- 
2.2.2

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