On Mon, Mar 16, 2015 at 03:14:14PM -0700, Thiago Macieira wrote: > On Monday 16 March 2015 14:44:20 Kees Cook wrote: > > > O_CLOEXEC > > > Set the close-on-exec flag on the new file > > >descriptor. See the description of the O_CLOEXEC flag in open(2) for > > >reasons why this may be useful. > > > > This begs the question: what happens when all CLONE_FD fds for a > > process are closed? Will the parent get SIGCHLD instead, will it > > auto-reap, or will it be un-wait-able (I assume not this...) > > Depends on CLONE_AUTOREAP. If it's on, then no one gets SIGCHLD, no one can > wait() on it and the process autoreaps itself. Minor nit: CLONE_AUTOREAP makes the process autoreap and nobody can wait on it, but if you pass SIGCHLD or some other exit signal to clone then you'll still get that signal. > If it's no active, then the old rules apply: parent gets SIGCHILD and can > wait(). If the parent exited first, then the child gets reparented to init, > which can do the wait(). Right. > A child without CLONE_AUTOREAP should be wait()able. If it gets wait()ed > before the clonefd is read, the clonefd() will return a 0 read. If it gets > read before wait, then wait() reaps another child or returns -ECHILD. That's > no different than two threads doing simultaneous wait() on the same child. Hrm? That isn't the semantics we implemented; you'll *always* get an exit notification via the clonefd if you have it open, with or without autoreap and whether or not a wait has occurred yet. And reading from the clonefd does not serve as a wait; if you don't pass CLONE_AUTOREAP, you'll still need to wait on the process. - Josh Triplett -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
