From d95baf08082ed514301f243f333970fdb217b286 Mon Sep 17 00:00:00 2001 From: Leo Yan Date: Fri, 11 Oct 2019 17:19:42 +0800 Subject: [PATCH] perf test: Avoid infinite loop for task exit case BugLink: https://bugs.launchpad.net/bugs/1860490 [ Upstream commit 791ce9c48c79210d2ffcdbe69421e7783b32921f ] When executing the task exit testing case, perf gets stuck in an endless loop this case and doesn't return back on Arm64 Juno board. After digging 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 a PMU event that 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 Cc: Alexander Shishkin Cc: Jiri Olsa Cc: Mark Rutland Cc: Namhyung Kim Link: http://lore.kernel.org/lkml/20191011091942.29841-2-leo.yan@linaro.org Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin Signed-off-by: Kamal Mostafa Signed-off-by: Khalid Elmously --- 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 788b0805d2f1..3986fd162a7e 100644 --- a/tools/perf/tests/task-exit.c +++ b/tools/perf/tests/task-exit.c @@ -48,6 +48,7 @@ int test__task_exit(struct test *test __maybe_unused, int subtest __maybe_unused struct cpu_map *cpus; struct thread_map *threads; struct perf_mmap *md; + int retry_count = 0; signal(SIGCHLD, sig_handler); @@ -127,6 +128,13 @@ retry: out_init: if (!exited || !nr_exit) { perf_evlist__poll(evlist, -1); + + if (retry_count++ > 1000) { + pr_debug("Failed after retrying 1000 times\n"); + err = -1; + goto out_free_maps; + } + goto retry; } -- 2.39.5