Hi again,
On Thu, Mar 14, 2024 at 02:40:45PM +0500, Muhammad Usama Anjum wrote:
> The atexit() is called from parent process as well as forked processes.
> Hence the child restores the settings at exit while the parent is still
> executing. Fix this by checking pid of atexit() calling process and only
> restore THP number from parent process.
>
> Fixes: c23ea61726d5 ("selftests/mm: protection_keys: save/restore nr_hugepages settings")
> Tested-by: Joey Gouly <joey.gouly@xxxxxxx>
> Signed-off-by: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
> ---
> tools/testing/selftests/mm/protection_keys.c | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/mm/protection_keys.c b/tools/testing/selftests/mm/protection_keys.c
> index f822ae31af22e..374a308174d2b 100644
> --- a/tools/testing/selftests/mm/protection_keys.c
> +++ b/tools/testing/selftests/mm/protection_keys.c
> @@ -1745,9 +1745,12 @@ void pkey_setup_shadow(void)
> shadow_pkey_reg = __read_pkey_reg();
> }
>
> +pid_t parent_pid;
> +
> void restore_settings_atexit(void)
> {
> - cat_into_file(buf, "/proc/sys/vm/nr_hugepages");
> + if (parent_pid == getpid())
> + cat_into_file(buf, "/proc/sys/vm/nr_hugepages");
> }
>
> void save_settings(void)
> @@ -1773,6 +1776,7 @@ void save_settings(void)
> exit(__LINE__);
> }
>
> + parent_pid = getpid();
> atexit(restore_settings_atexit);
> close(fd);
> }
After more testing, this is not actually enough. It passes sometimes, which is
why I gave my Tested-by, but it can still fail the same way as I originally
said.
assert() at protection_keys.c::812 test_nr: 19 iteration: 1
running abort_hooks()...
errno at assert: 12
I think the parent process needs to wait for all it's child processes (recursively).
This is due to the test_pkey_alloc_exhaust() calling become_child(), where it
exits, and that exit may be from the original PID.
Thanks,
Joey
