-stable review patch. If anyone has any objections, please let us know. ------------------ From: Lepton Wu commit a24864a1d52a97e345a6bd4862a057f98364d098 uml: definitively kill subprocesses on panic In a stock 2.6.22.6 kernel, poweroff a user mode linux guest (2.6.22.6 running in skas0 mode) will halt the host linux. I think the reason is the kernel thread abort because of a bug. Then the sys_reboot in process of user mode linux guest is not trapped by the user mode linux kernel and is executed by host. I think it is better to make sure all of our children process to quit when user mode linux kernel abort. [ jdike - the kernel process needs to ignore SIGTERM, plus the waitpid/kill loop is needed to make sure that all of our children are dead before the kernel exits ] Signed-off-by: Lepton Wu Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/um/os-Linux/skas/process.c | 2 +- arch/um/os-Linux/util.c | 38 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 39 insertions(+), 1 deletion(-) --- a/arch/um/os-Linux/skas/process.c +++ b/arch/um/os-Linux/skas/process.c @@ -182,7 +182,7 @@ static int userspace_tramp(void *stack) ptrace(PTRACE_TRACEME, 0, 0, 0); - init_new_thread_signals(); + signal(SIGTERM, SIG_DFL); err = set_interval(1); if(err) panic("userspace_tramp - setting timer failed, errno = %d\n", --- a/arch/um/os-Linux/util.c +++ b/arch/um/os-Linux/util.c @@ -105,6 +105,44 @@ int setjmp_wrapper(void (*proc)(void *, void os_dump_core(void) { + int pid; + signal(SIGSEGV, SIG_DFL); + + /* + * We are about to SIGTERM this entire process group to ensure that + * nothing is around to run after the kernel exits. The + * kernel wants to abort, not die through SIGTERM, so we + * ignore it here. + */ + + signal(SIGTERM, SIG_IGN); + kill(0, SIGTERM); + /* + * Most of the other processes associated with this UML are + * likely sTopped, so give them a SIGCONT so they see the + * SIGTERM. + */ + kill(0, SIGCONT); + + /* + * Now, having sent signals to everyone but us, make sure they + * die by ptrace. Processes can survive what's been done to + * them so far - the mechanism I understand is receiving a + * SIGSEGV and segfaulting immediately upon return. There is + * always a SIGSEGV pending, and (I'm guessing) signals are + * processed in numeric order so the SIGTERM (signal 15 vs + * SIGSEGV being signal 11) is never handled. + * + * Run a waitpid loop until we get some kind of error. + * Hopefully, it's ECHILD, but there's not a lot we can do if + * it's something else. Tell os_kill_ptraced_process not to + * wait for the child to report its death because there's + * nothing reasonable to do if that fails. + */ + + while ((pid = waitpid(-1, NULL, WNOHANG)) > 0) + os_kill_ptraced_process(pid, 0); + abort(); } -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/