From e2c29624f55e2f2f265a1c42b256f726ca1dee39 Mon Sep 17 00:00:00 2001
From: cl <cl@NetBSD.org>
Date: Wed, 12 Nov 2003 21:27:46 +0000
Subject: [PATCH] Prevent sa_newcachelwp() from creating new LWPs when the
 process is exiting. This should fix PR 23418 which was also reported by
 Thomas Klausner and Ian Fry (who also provided core dumps for analysis -
 thanks!).

Also g/c sa_yieldcall since it's now safe to put LWPs back into the cache.
Also return stacks in failure case.
---
 sys/kern/kern_sa.c | 68 +++++++++++++++-------------------------------
 sys/sys/savar.h    |  3 +-
 2 files changed, 23 insertions(+), 48 deletions(-)

diff --git a/sys/kern/kern_sa.c b/sys/kern/kern_sa.c
index 5d9ffc6858b6..8e81af1cd914 100644
--- a/sys/kern/kern_sa.c
+++ b/sys/kern/kern_sa.c
@@ -1,4 +1,4 @@
-/*	$NetBSD: kern_sa.c,v 1.41 2003/11/07 18:37:41 cl Exp $	*/
+/*	$NetBSD: kern_sa.c,v 1.42 2003/11/12 21:27:46 cl Exp $	*/
 
 /*-
  * Copyright (c) 2001 The NetBSD Foundation, Inc.
@@ -37,7 +37,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_sa.c,v 1.41 2003/11/07 18:37:41 cl Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_sa.c,v 1.42 2003/11/12 21:27:46 cl Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -750,31 +750,34 @@ sa_switch(struct lwp *l, int type)
 			return;
 		}
 
+		if (sa->sa_nstacks == 0) {
+#ifdef DIAGNOSTIC
+			printf("sa_switch(%d.%d flag %x): Not enough stacks.\n",
+			    p->p_pid, l->l_lid, l->l_flag);
+#endif
+			sa_putcachelwp(p, l2); /* PHOLD from sa_getcachelwp */
+			mi_switch(l, NULL);
+			return;
+		}
+
 		/*
 		 * XXX We need to allocate the sadata_upcall structure here,
 		 * XXX since we can't sleep while waiting for memory inside
 		 * XXX sa_upcall().  It would be nice if we could safely
 		 * XXX allocate the sadata_upcall structure on the stack, here.
 		 */
-
-		if (sa->sa_nstacks == 0) {
-#ifdef DIAGNOSTIC
-			printf("sa_switch(%d.%d flag %x): Not enough stacks.\n",
-			    p->p_pid, l->l_lid, l->l_flag);
-#endif
-			goto sa_upcall_failed;
-		}
-
 		sau = sadata_upcall_alloc(0);
 		if (sau == NULL) {
 #ifdef DIAGNOSTIC
 			printf("sa_switch(%d.%d): "
 			    "couldn't allocate upcall data.\n",
 			    p->p_pid, l->l_lid);
-
 #endif
-			goto sa_upcall_failed;
+			sa_putcachelwp(p, l2); /* PHOLD from sa_getcachelwp */
+			mi_switch(l, NULL);
+			return;
 		}
+
 		st = sa->sa_stacks[--sa->sa_nstacks];
 		DPRINTFN(9,("sa_switch(%d.%d) nstacks--   = %2d\n", 
 		    l->l_proc->p_pid, l->l_lid, sa->sa_nstacks));
@@ -787,7 +790,10 @@ sa_switch(struct lwp *l, int type)
 			printf("sa_switch(%d.%d): Error %d from sa_upcall()\n",
 			    p->p_pid, l->l_lid, error);
 #endif
-			goto sa_upcall_failed;
+			sa->sa_stacks[sa->sa_nstacks++] = st;
+			sa_putcachelwp(p, l2); /* PHOLD from sa_getcachelwp */
+			mi_switch(l, NULL);
+			return;
 		}
 
 		/* 
@@ -842,13 +848,6 @@ sa_switch(struct lwp *l, int type)
 	} else {
 		/* NOTREACHED */
 		panic("sa_vp empty");
-
-	sa_upcall_failed:
-		cpu_setfunc(l2, sa_yieldcall, l2);
-
-		l2->l_priority = l2->l_usrpri;
-		setrunnable(l2);
-		PRELE(l2); /* Remove the artificial hold-count */
 	}
 
 	DPRINTFN(4,("sa_switch(%d.%d) switching to LWP %d.\n",
@@ -888,31 +887,6 @@ sa_switchcall(void *arg)
 	upcallret(l);
 }
 
-void
-sa_yieldcall(void *arg)
-{
-	struct lwp *l;
-	struct proc *p;
-	struct sadata *sa;
-
-	l = arg;
-	p = l->l_proc;
-	sa = p->p_sa;
-	sa->sa_vp = l;
-
-	DPRINTFN(6,("sa_yieldcall(%d.%d)\n", p->p_pid, l->l_lid));
-
-	if (LIST_EMPTY(&sa->sa_lwpcache)) {
-		/* Allocate the next cache LWP */
-		DPRINTFN(6,("sa_yieldcall(%d.%d) allocating LWP\n",
-		    p->p_pid, l->l_lid));
-		sa_newcachelwp(l);
-	}
-
-	sa_yield(l);
-	upcallret(l);
-}
-
 static int
 sa_newcachelwp(struct lwp *l)
 {
@@ -923,6 +897,8 @@ sa_newcachelwp(struct lwp *l)
 	int s;
 
 	p = l->l_proc;
+	if (p->p_flag & P_WEXIT)
+		return (0);
 
 	inmem = uvm_uarea_alloc(&uaddr);
 	if (__predict_false(uaddr == 0)) {
diff --git a/sys/sys/savar.h b/sys/sys/savar.h
index e0f7b39eed98..ab560cbf3fa8 100644
--- a/sys/sys/savar.h
+++ b/sys/sys/savar.h
@@ -1,4 +1,4 @@
-/*	$NetBSD: savar.h,v 1.11 2003/11/03 22:34:51 cl Exp $	*/
+/*	$NetBSD: savar.h,v 1.12 2003/11/12 21:27:46 cl Exp $	*/
 
 /*-
  * Copyright (c) 2001 The NetBSD Foundation, Inc.
@@ -116,7 +116,6 @@ void	sa_switch(struct lwp *, int);
 void	sa_preempt(struct lwp *);
 void	sa_yield(struct lwp *);
 void	sa_switchcall(void *);
-void	sa_yieldcall(void *);
 int	sa_upcall(struct lwp *, int, struct lwp *, struct lwp *, size_t, void *);
 int	sa_upcall0(struct lwp *, int, struct lwp *, struct lwp *,
 	    size_t, void *, struct sadata_upcall *, stack_t *);