Avoid a race condition while swapping in a process.

Tested by mickey@, henning@, ericj@, and beck@.
ok mickey@

3 files changed, 25 insertions, 12 deletions

diff --git a/sys/arch/alpha/alpha/machdep.c b/sys/arch/alpha/alpha/machdep.c
index 5d5688589db..1c4f30c35c9 100644
--- a/sys/arch/alpha/alpha/machdep.c
+++ b/sys/arch/alpha/alpha/machdep.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: machdep.c,v 1.83 2003/08/10 00:03:21 miod Exp $ */
+/* $OpenBSD: machdep.c,v 1.84 2003/11/08 06:11:11 nordin Exp $ */
 /* $NetBSD: machdep.c,v 1.210 2000/06/01 17:12:38 thorpej Exp $ */
 
 /*-
@@ -1891,7 +1891,6 @@ fpusave_proc(struct proc *p, int save)
 #endif
 
 	KDASSERT(p->p_addr != NULL);
-	KDASSERT(p->p_flag & P_INMEM);
 
 	oci = p->p_addr->u_pcb.pcb_fpcpu;
 	if (oci == NULL) {
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index c7a01a41188..5f3e766c566 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: proc.h,v 1.67 2003/08/21 18:56:07 tedu Exp $	*/
+/*	$OpenBSD: proc.h,v 1.68 2003/11/08 06:11:11 nordin Exp $	*/
 /*	$NetBSD: proc.h,v 1.44 1996/04/22 01:23:21 christos Exp $	*/
 
 /*-
@@ -263,6 +263,7 @@ struct	proc {
 #define P_INEXEC	0x200000	/* Process is doing an exec right now */
 #define P_SYSTRACE	0x400000	/* Process system call tracing active*/
 #define P_CONTINUED	0x800000	/* Proc has continued from a stopped state. */
+#define P_SWAPIN	0x1000000	/* Swapping in right now */
 
 #define	P_BITS \
     ("\20\01ADVLOCK\02CTTY\03INMEM\04NOCLDSTOP\05PPWAIT\06PROFIL\07SELECT" \
diff --git a/sys/uvm/uvm_glue.c b/sys/uvm/uvm_glue.c
index f0136230b12..883f8e602ec 100644
--- a/sys/uvm/uvm_glue.c
+++ b/sys/uvm/uvm_glue.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_glue.c,v 1.35 2003/08/10 00:04:50 miod Exp $	*/
+/*	$OpenBSD: uvm_glue.c,v 1.36 2003/11/08 06:11:10 nordin Exp $	*/
 /*	$NetBSD: uvm_glue.c,v 1.44 2001/02/06 19:54:44 eeh Exp $	*/
 
 /* 
@@ -352,6 +352,14 @@ uvm_swapin(p)
 	vaddr_t addr;
 	int rv, s;
 
+	s = splstatclock();
+	if (p->p_flag & P_SWAPIN) {
+		splx(s);
+		return;
+	}
+	p->p_flag |= P_SWAPIN;
+	splx(s);
+
 	addr = (vaddr_t)p->p_addr;
 	/* make P_INMEM true */
 	if ((rv = uvm_fault_wire(kernel_map, addr, addr + USPACE,
@@ -367,6 +375,7 @@ uvm_swapin(p)
 	if (p->p_stat == SRUN)
 		setrunqueue(p);
 	p->p_flag |= P_INMEM;
+	p->p_flag &= ~P_SWAPIN;
 	splx(s);
 	p->p_swtime = 0;
 	++uvmexp.swapins;
@@ -552,20 +561,18 @@ uvm_swapout(p)
 #ifdef DEBUG
 	if (swapdebug & SDB_SWAPOUT)
 		printf("swapout: pid %d(%s)@%p, stat %x pri %d free %d\n",
-	   p->p_pid, p->p_comm, p->p_addr, p->p_stat,
-	   p->p_slptime, uvmexp.free);
+		    p->p_pid, p->p_comm, p->p_addr, p->p_stat,
+		    p->p_slptime, uvmexp.free);
 #endif
 
 	/*
-	 * Do any machine-specific actions necessary before swapout.
-	 * This can include saving floating point state, etc.
-	 */
-	cpu_swapout(p);
-
-	/*
 	 * Mark it as (potentially) swapped out.
 	 */
 	s = splstatclock();
+	if (!(p->p_flag & P_INMEM)) {
+		splx(s);
+		return;
+	}
 	p->p_flag &= ~P_INMEM;
 	if (p->p_stat == SRUN)
 		remrunqueue(p);
@@ -574,6 +581,12 @@ uvm_swapout(p)
 	++uvmexp.swapouts;
 
 	/*
+	 * Do any machine-specific actions necessary before swapout.
+	 * This can include saving floating point state, etc.
+	 */
+	cpu_swapout(p);
+
+	/*
 	 * Unwire the to-be-swapped process's user struct and kernel stack.
 	 */
 	addr = (vaddr_t)p->p_addr;