On 06/14, Roland McGrath wrote: > > > Hmm. Even without debugger, the parent doesn't react to SIGSTOP. > > Yes. It's been a long time since I thought about the vfork stuff much. > But I now recall thinking about the SIGSTOP/SIGTSTP issue too. It does > seem bad. OTOH, it has lurked there for many years now without complaints. > > Note that supporting stop/fatal signals in the normal way means that the > call has to return and pass the syscall-exit tracing point first. This > means a change in the order of events seen by a debugger. It also > complicates the subject of PTRACE_EVENT_VFORK_DONE reports, which today > happen before syscall-exit or signal stuff is possible. For proper > stopping in the normal way, the vfork-wait would be restarted via > sys_restart_syscall or something. Yes. I was thinking about this too. The parent can play with real_blocked or saved_sigmask to block all signals except STOP and KILL, use TASK_INTERRUPTIBLE for wait, and just return ERESTART each time it gets the signal (it should clear child->vfork_done if fatal_signal_pending). We should also check PF_KTHREAD though, there are in kernel users of CLONE_VFORK. > Bu the way that happens ordinarily is > to get all the way back to user mode and reenter with a normal syscall. > That doesn't touch the user stack itself, but it sure makes one nervous. me too. Especially because I do not really know how !x86 machines implement this all. We should also verify that the exiting/stopping parent can never write to its ->mm. For example, exit_mm() does put_user(tsk->clear_child_tid). Fortunately we can rely on PF_SIGNALED flag in this case. Oleg. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>