On Fri, Oct 12, 2018 at 05:33:35PM -0700, Enke Chen wrote: > For simplicity and consistency, this patch provides an implementation > for signal-based fault notification prior to the coredump of a child > process. A new prctl command, PR_SET_PREDUMP_SIG, is defined that can > be used by an application to express its interest and to specify the > signal (SIGCHLD or SIGUSR1 or SIGUSR2) for such a notification. A new > signal code (si_code), CLD_PREDUMP, is also defined for SIGCHLD. > > Background: > > As the coredump of a process may take time, in certain time-sensitive > applications it is necessary for a parent process (e.g., a process > manager) to be notified of a child's imminent death before the coredump > so that the parent process can act sooner, such as re-spawning an > application process, or initiating a control-plane fail-over. > > Currently there are two ways for a parent process to be notified of a > child process's state change. One is to use the POSIX signal, and > another is to use the kernel connector module. The specific events and > actions are summarized as follows: > > Process Event POSIX Signal Connector-based > ---------------------------------------------------------------------- > ptrace_attach() do_notify_parent_cldstop() proc_ptrace_connector() > SIGCHLD / CLD_STOPPED > > ptrace_detach() do_notify_parent_cldstop() proc_ptrace_connector() > SIGCHLD / CLD_CONTINUED > > pre_coredump/ N/A proc_coredump_connector() > get_signal() > > post_coredump/ do_notify_parent() proc_exit_connector() > do_exit() SIGCHLD / exit_signal > ---------------------------------------------------------------------- > > As shown in the table, the signal-based pre-coredump notification is not > currently available. In some cases using a connector-based notification > can be quite complicated (e.g., when a process manager is written in shell > scripts and thus is subject to certain inherent limitations), and a > signal-based notification would be simpler and better suited. > > Signed-off-by: Enke Chen <enkechen@xxxxxxxxx> > --- > arch/x86/kernel/signal_compat.c | 2 +- > include/linux/sched.h | 4 ++ > include/linux/signal.h | 5 +++ > include/uapi/asm-generic/siginfo.h | 3 +- > include/uapi/linux/prctl.h | 4 ++ > kernel/fork.c | 1 + > kernel/signal.c | 51 +++++++++++++++++++++++++ > kernel/sys.c | 77 ++++++++++++++++++++++++++++++++++++++ > 8 files changed, 145 insertions(+), 2 deletions(-) Shouldn't there also be a manpage update, and a kselftest added for this new user/kernel api that is being created? thanks, greg k-h
