On 06/26, Andy Lutomirski wrote: > > kthread_stop is *sick*. > > struct kthread self; > > ... > > current->vfork_done = &self.exited; > > ... > > do_exit(ret); > > And then some other thread goes and waits for the completion, which is > *on the stack*, which, in any sane world (e.g. with my series > applied), is long gone by then.
Yes, I forgot this when we discussed the problems with ti->flags/etc... > But this is broken even without any changes: since when is gcc > guaranteed to preserve the stack contents when a function ends with a > sibling call, let alone with a __noreturn call? I don't know if gcc can actually drop the stack frame in this case, but even if it can this looks fixeable. > Is there seriously no way to directly wait for a struct task_struct to > exit? Could we, say, kmalloc the completion (or maybe even the whole > struct kthread) and (ick!) hang it off ->vfork_done? Sure we can... And yes, I think we need to alloc the whole struct kthread. Just another (unfortunate) complication, the current code is simple. And probably kthread/kthread_stop should switch to task_work_exit(). Oleg.
