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().
v1->v2 changes: - Handled comment by Peter Zijlstra to remove locking for PF_EXIT_NOTIFY task->flags. - Added error handling in thread.c
v->v1 changes: - Handled comment by Simon Horman to remove unused err in cn_proc.c - Handled comment by Simon Horman to make adata and key_display static in cn_hash_test.c
Anjali Kulkarni (3): connector/cn_proc: Add hash table for threads connector/cn_proc: Kunit tests for threads hash table connector/cn_proc: Selftest for threads
drivers/connector/Makefile | 2 +- drivers/connector/cn_hash.c | 240 ++++++++++++++++++ drivers/connector/cn_proc.c | 55 +++- drivers/connector/connector.c | 96 ++++++- include/linux/connector.h | 47 ++++ include/linux/sched.h | 2 +- include/uapi/linux/cn_proc.h | 4 +- lib/Kconfig.debug | 17 ++ lib/Makefile | 1 + lib/cn_hash_test.c | 167 ++++++++++++ lib/cn_hash_test.h | 12 + tools/testing/selftests/connector/Makefile | 23 +- .../testing/selftests/connector/proc_filter.c | 5 + tools/testing/selftests/connector/thread.c | 116 +++++++++ .../selftests/connector/thread_filter.c | 96 +++++++ 15 files changed, 873 insertions(+), 10 deletions(-) create mode 100644 drivers/connector/cn_hash.c create mode 100644 lib/cn_hash_test.c create mode 100644 lib/cn_hash_test.h create mode 100644 tools/testing/selftests/connector/thread.c create mode 100644 tools/testing/selftests/connector/thread_filter.c