From 7eaa8c969efa77127de9a05856eef9e5d22cf487 Mon Sep 17 00:00:00 2001 From: Peter Xu Date: Fri, 26 Oct 2018 15:09:17 -0700 Subject: [PATCH] userfaultfd: selftest: recycle lock threads first Now we recycle the uffd servicing threads earlier than the lock threads. It might happen that when the lock thread is still blocked at a pthread mutex lock while the servicing thread has already quitted for the cpu so the lock thread will be blocked forever and hang the test program. To fix the possible race, recycle the lock threads first. This never happens with current missing-only tests, but when I start to run the write-protection tests (the feature is not yet posted upstream) it happens every time of the run possibly because in that new test we'll need to service two page faults for each lock operation. Link: http://lkml.kernel.org/r/20180930074259.18229-4-peterx@redhat.com Signed-off-by: Peter Xu Acked-by: Mike Rapoport Cc: Shuah Khan Cc: Mike Kravetz Cc: Jerome Glisse Cc: Zi Yan Cc: "Kirill A . Shutemov" Cc: Shaohua Li Cc: Andrea Arcangeli Cc: "Dr . David Alan Gilbert" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- tools/testing/selftests/vm/userfaultfd.c | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c index 7a8c6937cc67..5d1db824f73a 100644 --- a/tools/testing/selftests/vm/userfaultfd.c +++ b/tools/testing/selftests/vm/userfaultfd.c @@ -626,6 +626,12 @@ static int stress(unsigned long *userfaults) if (uffd_test_ops->release_pages(area_src)) return 1; + + finished = 1; + for (cpu = 0; cpu < nr_cpus; cpu++) + if (pthread_join(locking_threads[cpu], NULL)) + return 1; + for (cpu = 0; cpu < nr_cpus; cpu++) { char c; if (bounces & BOUNCE_POLL) { @@ -643,11 +649,6 @@ static int stress(unsigned long *userfaults) } } - finished = 1; - for (cpu = 0; cpu < nr_cpus; cpu++) - if (pthread_join(locking_threads[cpu], NULL)) - return 1; - return 0; } -- 2.11.0