linux-kernel - [PATCH net-next 0/2] Threads extension for process connector

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Message-ID: <20240920000933.185090-1-anjali.k.kulkarni@oracle.com>
Date: Thu, 19 Sep 2024 17:09:31 -0700
From: Anjali Kulkarni <anjali.k.kulkarni@...cle.com>
To: davem@...emloft.net, Liam.Howlett@...cle.com
Cc: edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, oleg@...hat.com,
        akpm@...ux-foundation.org, axboe@...nel.dk, brauner@...nel.org,
        mhocko@...e.com, alexjlzheng@...cent.com, willy@...radead.org,
        michael.christie@...cle.com, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, shuah@...nel.org,
        linux-kselftest@...r.kernel.org, anjali.k.kulkarni@...cle.com,
        peili.io@...cle.com
Subject: [PATCH net-next 0/2] Threads extension for process connector

Recently we committed a fix to allow processes to receive notifications for
non-zero exits via the process connector module. Commit is a4c9a56e6a2c.

However, for threads, when it does a pthread_exit(&exit_status) call, the
kernel is not aware of the exit status with which pthread_exit is called.
It is sent by child thread to the parent process, if it is waiting in
pthread_join(). Hence, for a thread exiting abnormally, kernel cannot
send notifications to any listening processes.

The exception to this is if the thread is sent a signal which it has not
handled, and dies along with it's process as a result; for eg. SIGSEGV or
SIGKILL. In this case, kernel is aware of the non-zero exit and sends a
notification for it.

For our use case, we cannot have parent wait in pthread_join, one of the
main reasons for this being that we do not want to track normal
pthread_exit(), which could be a very large number. We only want to be
notified of any abnormal exits. Hence, threads are created with
pthread_attr_t set to PTHREAD_CREATE_DETACHED.

To fix this problem, we add a new type PROC_CN_MCAST_NOTIFY to proc connector
API, which allows a thread to send it's exit status to kernel either when
it needs to call pthread_exit() with non-zero value to indicate some
error or from signal handler before pthread_exit().

Anjali Kulkarni (2):
  connector/cn_proc: Handle threads for proc connector
  connector/cn_proc: Selftest for threads case

 drivers/connector/cn_proc.c                   | 11 ++-
 include/linux/cn_proc.h                       |  5 +-
 include/uapi/linux/cn_proc.h                  |  4 +-
 kernel/exit.c                                 |  5 +-
 tools/testing/selftests/connector/Makefile    | 23 ++++-
 .../testing/selftests/connector/proc_filter.c |  5 +
 tools/testing/selftests/connector/thread.c    | 87 +++++++++++++++++
 .../selftests/connector/thread_filter.c       | 93 +++++++++++++++++++
 8 files changed, 226 insertions(+), 7 deletions(-)
 create mode 100644 tools/testing/selftests/connector/thread.c
 create mode 100644 tools/testing/selftests/connector/thread_filter.c

-- 
2.45.2