LKML Archive on
 help / color / Atom feed
From: Leo Yan <>
To: Arnaldo Carvalho de Melo <>,
	Mark Rutland <>,
	Alexander Shishkin <>,
	Jiri Olsa <>, Namhyung Kim <>,
Cc: Leo Yan <>
Subject: [PATCH v1 2/2] perf test: Avoid infinite loop for task exit case
Date: Fri, 11 Oct 2019 17:19:42 +0800
Message-ID: <> (raw)
In-Reply-To: <>

When execute task exit testing case, Perf tool stucks in this case and
doesn't return back on Arm64 Juno board.

After dig into this issue, since Juno board has Arm's big.LITTLE CPUs,
thus the PMUs are not compatible between the big CPUs and little CPUs.
This leads to PMU event cannot be enabled properly when the traced task
is migrated from one variant's CPU to another variant.  Finally, the
test case runs into infinite loop for cannot read out any event data
after return from polling.

Eventually, we need to work out formal solution to allow PMU events can
be freely migrated from one CPU variant to another, but this is a
difficult task and a different topic.  This patch tries to fix the Perf
test case to avoid infinite loop, when the testing detects 1000 times
retrying for reading empty events, it will directly bail out and return
failure.  This allows the Perf tool can continue its other test cases.

Signed-off-by: Leo Yan <>
 tools/perf/tests/task-exit.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/tests/task-exit.c b/tools/perf/tests/task-exit.c
index ca0a6ca43b13..d85c9f608564 100644
--- a/tools/perf/tests/task-exit.c
+++ b/tools/perf/tests/task-exit.c
@@ -53,6 +53,7 @@ int test__task_exit(struct test *test __maybe_unused, int subtest __maybe_unused
 	struct perf_cpu_map *cpus;
 	struct perf_thread_map *threads;
 	struct mmap *md;
+	int retry_count = 0;
 	signal(SIGCHLD, sig_handler);
@@ -132,6 +133,13 @@ int test__task_exit(struct test *test __maybe_unused, int subtest __maybe_unused
 	if (!exited || !nr_exit) {
 		evlist__poll(evlist, -1);
+		if (retry_count++ > 1000) {
+			pr_debug("Failed after retrying 1000 times\n");
+			err = -1;
+			goto out_free_maps;
+		}
 		goto retry;

  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-11  9:19 [PATCH v1 1/2] perf test: Report failure for mmap events Leo Yan
2019-10-11  9:19 ` Leo Yan [this message]
2019-10-11 14:38   ` [PATCH v1 2/2] perf test: Avoid infinite loop for task exit case Arnaldo Carvalho de Melo
2019-10-14 14:11   ` Arnaldo Carvalho de Melo
2019-10-15  3:20     ` Leo Yan
2019-10-21 23:19   ` [tip: perf/core] " tip-bot2 for Leo Yan
2019-10-14 14:09 ` [PATCH v1 1/2] perf test: Report failure for mmap events Arnaldo Carvalho de Melo
2019-10-21 23:19 ` [tip: perf/core] " tip-bot2 for Leo Yan

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

LKML Archive on

Archives are clonable:
	git clone --mirror lkml/git/0.git
	git clone --mirror lkml/git/1.git
	git clone --mirror lkml/git/2.git
	git clone --mirror lkml/git/3.git
	git clone --mirror lkml/git/4.git
	git clone --mirror lkml/git/5.git
	git clone --mirror lkml/git/6.git
	git clone --mirror lkml/git/7.git
	git clone --mirror lkml/git/8.git
	git clone --mirror lkml/git/9.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 lkml lkml/ \
	public-inbox-index lkml

Example config snippet for mirrors

Newsgroup available over NNTP:

AGPL code for this site: git clone