Re: [PATCH v2 1/3] pidfd: allow pidfd_open() on non-thread-group leaders

[Christian Brauner <brauner@kernel.org>]

On Mon, Dec 11, 2023 at 03:28:09PM +0800, kernel test robot wrote:
> 
> 
> Hello,
> 
> kernel test robot noticed "kernel-selftests.pidfd.pidfd_test.fail" on:
> 
> commit: e6d9be676d2c1fa8332c63c4382b8d3227fca991 ("[PATCH v2 1/3] pidfd: allow pidfd_open() on non-thread-group leaders")
> url: https://github.com/intel-lab-lkp/linux/commits/Tycho-Andersen/selftests-pidfd-add-non-thread-group-leader-tests/20231208-011135
> patch link: https://lore.kernel.org/all/20231207170946.130823-1-tycho@tycho.pizza/
> patch subject: [PATCH v2 1/3] pidfd: allow pidfd_open() on non-thread-group leaders
> 
> in testcase: kernel-selftests
> version: kernel-selftests-x86_64-60acb023-1_20230329
> with following parameters:
> 
> 	group: pidfd
> 
> 
> 
> compiler: gcc-12
> test machine: 36 threads 1 sockets Intel(R) Core(TM) i9-10980XE CPU @ 3.00GHz (Cascade Lake) with 32G memory
> 
> (please refer to attached dmesg/kmsg for entire log/backtrace)
> 
> 
> 
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <oliver.sang@intel.com>
> | Closes: https://lore.kernel.org/oe-lkp/202312111516.26dc3fd5-oliver.sang@intel.com
> 
> 
> besides, we also observed kernel-selftests.pidfd.pidfd_poll_test.fail on this
> commit, but clean on parent:
> 
> bee0e7762ad2c602 e6d9be676d2c1fa8332c63c4382
> ---------------- ---------------------------
>        fail:runs  %reproduction    fail:runs
>            |             |             |
>            :6          100%           6:6     kernel-selftests.pidfd.pidfd_poll_test.fail
>            :6          100%           6:6     kernel-selftests.pidfd.pidfd_test.fail
> 
> 
> 
> TAP version 13
> 1..7
> # timeout set to 300
> # selftests: pidfd: pidfd_test
> # TAP version 13
> # 1..8
> # # Parent: pid: 2191
> # # Parent: Waiting for Child (2192) to complete.
> # # Child (pidfd): starting. pid 2192 tid 2192
> # # Child Thread: starting. pid 2192 tid 2193 ; and sleeping
> # # Child Thread: doing exec of sleep
> # Bail out! pidfd_poll check for premature notification on child thread exec test: Unexpected epoll_wait result (c=0, events=0) (errno 0)

So it seems that this broke multi-threaded exit notifications.