From 880569296fb8989516be0492eb304cb88c879e5c Mon Sep 17 00:00:00 2001 From: Eirik Fuller Date: Fri, 25 Jun 2021 22:38:25 -0400 Subject: perf test: Handle fd gaps in test__dso_data_reopen https://github.com/beaker-project/restraint/issues/215 describes a file descriptor leak which revealed the test failure described here. The 'DSO data reopen' perf test assumes that RLIMIT_NOFILE limits the number of open file descriptors, but it actually limits newly opened file descriptors. When the file descriptor limit is reduced, file descriptors already open remain open regardless of the new limit. This test failure does not occur if open file descriptors are contiguous, beginning at zero. The following command triggers this perf test failure. perf test 'DSO data reopen' 3>/dev/null 8>/dev/null This patch determines the file descriptor limit by opening four files and then closing them. The limit is set to the fourth file descriptor, leaving only the first three available because any newly opened file descriptor must be less than the limit. Signed-off-by: Eirik Fuller Acked-by: Jiri Olsa Acked-by: Michael Petlan LPU-Reference: 20210626023825.1398547-1-efuller@redhat.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/tests/dso-data.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/tools/perf/tests/dso-data.c b/tools/perf/tests/dso-data.c index 627c1aaf1c9e..43e1b01e5afc 100644 --- a/tools/perf/tests/dso-data.c +++ b/tools/perf/tests/dso-data.c @@ -308,10 +308,20 @@ int test__dso_data_cache(struct test *test __maybe_unused, int subtest __maybe_u return 0; } +static long new_limit(int count) +{ + int fd = open("/dev/null", O_RDONLY); + long ret = fd; + if (count > 0) + ret = new_limit(--count); + close(fd); + return ret; +} + int test__dso_data_reopen(struct test *test __maybe_unused, int subtest __maybe_unused) { struct machine machine; - long nr_end, nr = open_files_cnt(); + long nr_end, nr = open_files_cnt(), lim = new_limit(3); int fd, fd_extra; #define dso_0 (dsos[0]) @@ -334,7 +344,7 @@ int test__dso_data_reopen(struct test *test __maybe_unused, int subtest __maybe_ /* Make sure we are able to open 3 fds anyway */ TEST_ASSERT_VAL("failed to set file limit", - !set_fd_limit((nr + 3))); + !set_fd_limit((lim))); TEST_ASSERT_VAL("failed to create dsos\n", !dsos__create(3, TEST_FILE_SIZE)); -- cgit v1.2.3