On 1/18/22 1:12 PM, Eric W. Biederman wrote: > Mike Christie <[email protected]> writes: > >> On 1/17/22 11:31 AM, Eric W. Biederman wrote: >>> Mike Christie <[email protected]> writes: >>> >>>> On 12/22/21 12:24 PM, Eric W. Biederman wrote: >>>>> All I am certain of is that you need to set >>>>> "args->exit_signal = -1;". This prevents having to play games with >>>>> do_notify_parent. >>>> >>>> Hi Eric, >>>> >>>> I have all your review comments handled except this one. It's looking like >>>> it's >>>> more difficult than just setting the exit_signal=-1, so I wanted to check >>>> that >>>> I understood you. >>> >>> [snip problems with exit_signal = -1] >>> >>>> >>>> What do you think? >>> >>> I was wrong. I appear to have confused the thread and the non-thread >>> cases. >>> >>> Perhaps I meant "args->exit_signal = 0". That looks like >>> do_notify_parent won't send it, and thread_group_leader continues to do >>> the right thing. >> >> That doesn't work too. exit_notify will call do_notify_parent but >> our parent, qemu, does not ignore SIGCHILD so we will not drop >> down in into this chunk: >> >> psig = tsk->parent->sighand; >> spin_lock_irqsave(&psig->siglock, flags); >> if (!tsk->ptrace && sig == SIGCHLD && >> (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN || >> (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) { >> >> do_notify_parent will return false and so autoreap in exit_notify will >> be false. > > Bah good point. We won't send the signal but you won't autoreap either. > > I think we could legitimately change this bit: > > /* > * Send with __send_signal as si_pid and si_uid are in the > * parent's namespaces. > */ > if (valid_signal(sig) && sig) > __send_signal(sig, &info, tsk->parent, PIDTYPE_TGID, false); > > To add: > else > /* We don't notify the parent so just autoreap */ > autoreap = true; >
Hey, This works for me, but I think we might have issues where threads now get reaped too soon when they are being ptraced. I think I found a simple solution by just using kernel_wait in the vhost task code since I want to wait for the thread to exit when I'm removing a device already. I posted a patchset so you can check it out. _______________________________________________ Virtualization mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/virtualization
