[src/trunk]: src/sys/uvm avoid taking locks that aren't initialised.

[mrg <mrg%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/47de0c361f7d
branches:  trunk
changeset: 983428:47de0c361f7d
user:      mrg <mrg%NetBSD.org@localhost>
date:      Sun May 23 00:36:36 2021 +0000

description:
avoid taking locks that aren't initialised.

fixes panic when typing 'reboot' at the askroot prompt.

diffstat:

 sys/uvm/uvm_swap.c |  9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diffs (44 lines):

diff -r 7439b6fbaac8 -r 47de0c361f7d sys/uvm/uvm_swap.c
--- a/sys/uvm/uvm_swap.c        Sat May 22 17:20:01 2021 +0000
+++ b/sys/uvm/uvm_swap.c        Sun May 23 00:36:36 2021 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_swap.c,v 1.203 2021/03/13 15:29:55 skrll Exp $     */
+/*     $NetBSD: uvm_swap.c,v 1.204 2021/05/23 00:36:36 mrg Exp $       */
 
 /*
  * Copyright (c) 1995, 1996, 1997, 2009 Matthew R. Green
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_swap.c,v 1.203 2021/03/13 15:29:55 skrll Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_swap.c,v 1.204 2021/05/23 00:36:36 mrg Exp $");
 
 #include "opt_uvmhist.h"
 #include "opt_compat_netbsd.h"
@@ -202,6 +202,7 @@
 /* locks */
 static kmutex_t uvm_swap_data_lock __cacheline_aligned;
 static krwlock_t swap_syscall_lock;
+bool uvm_swap_init_done = false;
 
 /* workqueue and use counter for swap to regular files */
 static int sw_reg_count = 0;
@@ -296,6 +297,8 @@
        pool_init(&vndbuf_pool, sizeof(struct vndbuf), 0, 0, 0, "swp vnd",
            NULL, IPL_BIO);
 
+       uvm_swap_init_done = true;
+
        UVMHIST_LOG(pdhist, "<- done", 0, 0, 0, 0);
 }
 
@@ -1141,6 +1144,8 @@
        struct vnode *vp;
        int error;
 
+       if (!uvm_swap_init_done)
+               return;
        printf("turning off swap...");
        rw_enter(&swap_syscall_lock, RW_WRITER);
        mutex_enter(&uvm_swap_data_lock);