Userspace doesn't know about PF_USER_WORKER threads, so it can't do wait
to clean them up. For cases like where qemu will do dynamic/hot add/remove
of vhost devices, then we need to auto reap the thread like was done for
the kthread case, because qemu does not know what API the kernel/vhost
layer is using.

This has us do autoreaping for these threads similar to when the parent
ignores SIGCHLD and for kthreads.

Signed-off-by: Mike Christie <michael.chris...@oracle.com>
---
 kernel/signal.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index 7c4b7ae714d4..07e7d6f9bf66 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2049,9 +2049,9 @@ bool do_notify_parent(struct task_struct *tsk, int sig)
 
        psig = tsk->parent->sighand;
        spin_lock_irqsave(&psig->siglock, flags);
-       if (!tsk->ptrace && sig == SIGCHLD &&
+       if (!tsk->ptrace && (tsk->flags & PF_USER_WORKER || (sig == SIGCHLD &&
            (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN ||
-            (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))) {
+            (psig->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT))))) {
                /*
                 * We are exiting and our parent doesn't care.  POSIX.1
                 * defines special semantics for setting SIGCHLD to SIG_IGN
-- 
2.25.1

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