From 053eb17635e19c5cfe8140d0d33dd9330bf6bc22 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Fri, 12 Mar 2021 09:48:20 -0800
Subject: [PATCH] Set TDP_KTHREAD before calling cpu_fork() and
 cpu_copy_thread().

This permits these routines to use special logic for initializing MD
kthread state.

For the kproc case, this required moving the logic to set these flags
from kproc_create() into do_fork().

Sponsored by:	Netflix

(cherry picked from commit 640d54045bdbf894ae3c75cd9818c29fc2f6e5e7)
---
 sys/kern/kern_fork.c    | 12 ++++++++++--
 sys/kern/kern_kthread.c | 17 +++++------------
 sys/sys/proc.h          |  1 +
 3 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/sys/kern/kern_fork.c b/sys/kern/kern_fork.c
index 870ae494de5..3da8205d8ab 100644
--- a/sys/kern/kern_fork.c
+++ b/sys/kern/kern_fork.c
@@ -497,9 +497,12 @@ do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *
 	} else {
 		sigacts_copy(newsigacts, p1->p_sigacts);
 		p2->p_sigacts = newsigacts;
-		if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0) {
+		if ((fr->fr_flags2 & (FR2_DROPSIG_CAUGHT | FR2_KPROC)) != 0) {
 			mtx_lock(&p2->p_sigacts->ps_mtx);
-			sig_drop_caught(p2);
+			if ((fr->fr_flags2 & FR2_DROPSIG_CAUGHT) != 0)
+				sig_drop_caught(p2);
+			if ((fr->fr_flags2 & FR2_KPROC) != 0)
+				p2->p_sigacts->ps_flag |= PS_NOCLDWAIT;
 			mtx_unlock(&p2->p_sigacts->ps_mtx);
 		}
 	}
@@ -511,6 +514,11 @@ do_fork(struct thread *td, struct fork_req *fr, struct proc *p2, struct thread *
 	else
 	        p2->p_sigparent = SIGCHLD;
 
+	if ((fr->fr_flags2 & FR2_KPROC) != 0) {
+		p2->p_flag |= P_SYSTEM | P_KPROC;
+		td2->td_pflags |= TDP_KTHREAD;
+	}
+
 	p2->p_textvp = p1->p_textvp;
 	p2->p_fd = fd;
 	p2->p_fdtol = fdtol;
diff --git a/sys/kern/kern_kthread.c b/sys/kern/kern_kthread.c
index d049a099847..32832bde2f5 100644
--- a/sys/kern/kern_kthread.c
+++ b/sys/kern/kern_kthread.c
@@ -95,6 +95,7 @@ kproc_create(void (*func)(void *), void *arg,
 
 	bzero(&fr, sizeof(fr));
 	fr.fr_flags = RFMEM | RFFDG | RFPROC | RFSTOPPED | flags;
+	fr.fr_flags2 = FR2_KPROC;
 	fr.fr_pages = pages;
 	fr.fr_procp = &p2;
 	error = fork1(&thread0, &fr);
@@ -105,21 +106,11 @@ kproc_create(void (*func)(void *), void *arg,
 	if (newpp != NULL)
 		*newpp = p2;
 
-	/* this is a non-swapped system process */
-	PROC_LOCK(p2);
-	td = FIRST_THREAD_IN_PROC(p2);
-	p2->p_flag |= P_SYSTEM | P_KPROC;
-	td->td_pflags |= TDP_KTHREAD;
-	mtx_lock(&p2->p_sigacts->ps_mtx);
-	p2->p_sigacts->ps_flag |= PS_NOCLDWAIT;
-	mtx_unlock(&p2->p_sigacts->ps_mtx);
-	PROC_UNLOCK(p2);
-
 	/* set up arg0 for 'ps', et al */
 	va_start(ap, fmt);
 	vsnprintf(p2->p_comm, sizeof(p2->p_comm), fmt, ap);
 	va_end(ap);
-	/* set up arg0 for 'ps', et al */
+	td = FIRST_THREAD_IN_PROC(p2);
 	va_start(ap, fmt);
 	vsnprintf(td->td_name, sizeof(td->td_name), fmt, ap);
 	va_end(ap);
@@ -295,12 +286,14 @@ kthread_add(void (*func)(void *), void *arg, struct proc *p,
 	TSTHREAD(newtd, newtd->td_name);
 
 	newtd->td_proc = p;  /* needed for cpu_copy_thread */
+	newtd->td_pflags |= TDP_KTHREAD;
+
 	/* might be further optimized for kthread */
 	cpu_copy_thread(newtd, oldtd);
+
 	/* put the designated function(arg) as the resume context */
 	cpu_fork_kthread_handler(newtd, func, arg);
 
-	newtd->td_pflags |= TDP_KTHREAD;
 	thread_cow_get_proc(newtd, p);
 
 	/* this code almost the same as create_thread() in kern_thr.c */
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 99257878c2e..783c3896298 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -1043,6 +1043,7 @@ struct	fork_req {
 	int 		fr_flags2;
 #define	FR2_DROPSIG_CAUGHT	0x00000001 /* Drop caught non-DFL signals */
 #define	FR2_SHARE_PATHS		0x00000002 /* Invert sense of RFFDG for paths */
+#define	FR2_KPROC		0x00000004 /* Create a kernel process */
 };
 
 /*
-- 
2.45.0