From 0ebabc93a454467be57821c02ac5182e1bb34699 Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Sat, 2 Dec 2000 01:32:51 +0000
Subject: [PATCH] Protect p_stat with sched_lock.

---
 sys/kern/sys_process.c | 16 +++++++++++++---
 sys/kern/tty.c         | 12 ++++++++++++
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/sys/kern/sys_process.c b/sys/kern/sys_process.c
index 533ba71f51d2..c9abad45c604 100644
--- a/sys/kern/sys_process.c
+++ b/sys/kern/sys_process.c
@@ -280,8 +280,12 @@ ptrace(curp, uap)
 			return EBUSY;
 
 		/* not currently stopped */
-		if (p->p_stat != SSTOP || (p->p_flag & P_WAITED) == 0)
+		mtx_enter(&sched_lock, MTX_SPIN);
+		if (p->p_stat != SSTOP || (p->p_flag & P_WAITED) == 0) {
+			mtx_exit(&sched_lock, MTX_SPIN);
 			return EBUSY;
+		}
+		mtx_exit(&sched_lock, MTX_SPIN);
 
 		/* OK */
 		break;
@@ -363,11 +367,17 @@ ptrace(curp, uap)
 	sendsig:
 		/* deliver or queue signal */
 		s = splhigh();
+		mtx_enter(&sched_lock, MTX_SPIN);
 		if (p->p_stat == SSTOP) {
 			p->p_xstat = uap->data;
 			setrunnable(p);
-		} else if (uap->data) {
-			psignal(p, uap->data);
+			mtx_exit(&sched_lock, MTX_SPIN);
+		} else {
+			mtx_exit(&sched_lock, MTX_SPIN);
+			if (uap->data) {
+				mtx_assert(&Giant, MA_OWNED);
+				psignal(p, uap->data);
+			}
 		}
 		splx(s);
 		return 0;
diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index 1117708cb982..ce11ea52017c 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -2254,6 +2254,7 @@ ttyinfo(tp)
 			if (proc_compare(pick, p))
 				pick = p;
 
+		mtx_enter(&sched_lock, MTX_SPIN);
 		ttyprintf(tp, " cmd: %s %d [%s] ", pick->p_comm, pick->p_pid,
 		    pick->p_stat == SRUN ? "running" :
 		    pick->p_wmesg ? pick->p_wmesg : "iowait");
@@ -2278,6 +2279,7 @@ ttyinfo(tp)
 		    pick->p_stat == SIDL || pick->p_stat == SWAIT ||
 		    pick->p_stat == SZOMB ? 0 :
 		    (long)pgtok(vmspace_resident_count(pick->p_vmspace)));
+		mtx_exit(&sched_lock, MTX_SPIN);
 	}
 	tp->t_rocount = 0;	/* so pending input will be retyped if BS */
 }
@@ -2308,15 +2310,20 @@ proc_compare(p1, p2)
 
 	if (p1 == NULL)
 		return (1);
+
+	mtx_enter(&sched_lock, MTX_SPIN);
 	/*
 	 * see if at least one of them is runnable
 	 */
 	switch (TESTAB(ISRUN(p1), ISRUN(p2))) {
 	case ONLYA:
+		mtx_exit(&sched_lock, MTX_SPIN);
 		return (0);
 	case ONLYB:
+		mtx_exit(&sched_lock, MTX_SPIN);
 		return (1);
 	case BOTH:
+		mtx_exit(&sched_lock, MTX_SPIN);
 		/*
 		 * tie - favor one with highest recent cpu utilization
 		 */
@@ -2331,12 +2338,17 @@ proc_compare(p1, p2)
 	 */
 	switch (TESTAB(p1->p_stat == SZOMB, p2->p_stat == SZOMB)) {
 	case ONLYA:
+		mtx_exit(&sched_lock, MTX_SPIN);
 		return (1);
 	case ONLYB:
+		mtx_exit(&sched_lock, MTX_SPIN);
 		return (0);
 	case BOTH:
+		mtx_exit(&sched_lock, MTX_SPIN);
 		return (p2->p_pid > p1->p_pid); /* tie - return highest pid */
 	}
+	mtx_exit(&sched_lock, MTX_SPIN);
+
 	/*
 	 * pick the one with the smallest sleep time
 	 */