On Sat, Sep 29, 2018 at 04:43:11PM +0800, Peter Xu wrote:
> 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.
>
> Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxxxxxx>
> ---
> 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 f79706f13ce7..a388675b15af 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -623,6 +623,12 @@ 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) {
> @@ -640,11 +646,6 @@ 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;
> }
>
> --
> 2.17.1
>
--
Sincerely yours,
Mike.
