On 5/17/23 10:49 PM, Eric W. Biederman wrote: > > Long story short. > > In the patch below the first hunk is a noop. > > The code you are bypassing was added to ensure that process termination > (aka SIGKILL) is processed before any other signals. Other than signal > processing order there are not any substantive differences in the two > code paths. With all signals except SIGSTOP == 19 and SIGKILL == 9 > blocked SIGKILL should always be processed before SIGSTOP. > > Can you try patch with just the last hunk that does > s/PF_IO_WORKER/PF_USER_WORKER/ and see if that is enough? > If I just have the last hunk and then we get SIGKILL what happens is in code like: vhost_worker() schedule() if (has IO) handle_IO() The schedule() calls will hit the signal_pending_state check for signal_pending or __fatal_signal_pending and so instead of waiting for whatever wake_up call we normally waited for we tend to just return immediately. If you just run Qemu (the parent of the vhost_task) and send SIGKILL then sometimes the vhost_task just spins and it would look like the task has taken over the CPU (this is what I hit when I tested Linus's patch). With the first hunk of the patch, we will end up dequeuing the SIGKILL and clearing TIF_SIGPENDING, so the vhost_task can still do some work before it exits. In the other patches we do: if (get_signal(ksig)) start_exit_cleanup_by_stopping_newIO() flush running IO() exit() But to do the flush running IO() part of this I need to wait for it so that's why I wanted to be able to dequeue the SIGKILL and clear the TIF_SIGPENDING bit. Or I don't need this specifically. In patch 0/8 I said I knew you guys would not like it :) If I just have a: if (fatal_signal()) clear_fatal_signal() then it would work for me. _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
