linux-kernel - [PATCH V6 05/10] signal: Perfom autoreap for PF_USER

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Message-Id: <20211129194707.5863-6-michael.christie@oracle.com>
Date:   Mon, 29 Nov 2021 13:47:02 -0600
From:   Mike Christie <michael.christie@...cle.com>
To:     geert@...ux-m68k.org, vverma@...italocean.com, hdanton@...a.com,
        hch@...radead.org, stefanha@...hat.com, jasowang@...hat.com,
        mst@...hat.com, sgarzare@...hat.com,
        virtualization@...ts.linux-foundation.org,
        christian.brauner@...ntu.com, axboe@...nel.dk,
        linux-kernel@...r.kernel.org
Cc:     Mike Christie <michael.christie@...cle.com>
Subject: [PATCH V6 05/10] signal: Perfom autoreap for PF_USER_WORKER

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.christie@...cle.com>
---
 kernel/signal.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/signal.c b/kernel/signal.c
index a629b11bf3e0..4ce2cc195269 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -2071,9 +2071,9 @@ 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