[src/netbsd-3-0]: src/sys/uvm Apply patch (requested by jld in ticket #1323):

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

details:   https://anonhg.NetBSD.org/src/rev/d563dec3d774
branches:  netbsd-3-0
changeset: 579263:d563dec3d774
user:      tron <tron%NetBSD.org@localhost>
date:      Fri Jul 28 12:32:37 2006 +0000

description:
Apply patch (requested by jld in ticket #1323):
Avoid a panic in page fault handling that can occur under low-memory
conditions.

diffstat:

 sys/uvm/uvm_bio.c |  31 ++++++++++++++++++++-----------
 1 files changed, 20 insertions(+), 11 deletions(-)

diffs (83 lines):

diff -r 3b496cd740af -r d563dec3d774 sys/uvm/uvm_bio.c
--- a/sys/uvm/uvm_bio.c Wed Jul 26 20:21:18 2006 +0000
+++ b/sys/uvm/uvm_bio.c Fri Jul 28 12:32:37 2006 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_bio.c,v 1.37.2.1 2005/08/24 18:43:38 riz Exp $     */
+/*     $NetBSD: uvm_bio.c,v 1.37.2.1.2.1 2006/07/28 12:32:37 tron Exp $        */
 
 /*
  * Copyright (c) 1998 Chuck Silvers.
@@ -34,7 +34,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_bio.c,v 1.37.2.1 2005/08/24 18:43:38 riz Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_bio.c,v 1.37.2.1.2.1 2006/07/28 12:32:37 tron Exp $");
 
 #include "opt_uvmhist.h"
 
@@ -302,8 +302,6 @@
        eva = ufi->orig_rvaddr + (npages << PAGE_SHIFT);
 
        UVMHIST_LOG(ubchist, "va 0x%lx eva 0x%lx", va, eva, 0, 0);
-       simple_lock(&uobj->vmobjlock);
-       uvm_lock_pageq();
        for (i = 0; va < eva; i++, va += PAGE_SIZE) {
                boolean_t rdonly;
                vm_prot_t mask;
@@ -327,12 +325,18 @@
                if (pg == NULL || pg == PGO_DONTCARE) {
                        continue;
                }
+
+               uobj = pg->uobject;
+               simple_lock(&uobj->vmobjlock);
                if (pg->flags & PG_WANTED) {
                        wakeup(pg);
                }
                KASSERT((pg->flags & PG_FAKE) == 0);
                if (pg->flags & PG_RELEASED) {
+                       uvm_lock_pageq();
                        uvm_pagefree(pg);
+                       uvm_unlock_pageq();
+                       simple_unlock(&uobj->vmobjlock);
                        continue;
                }
                if (pg->loan_count != 0) {
@@ -345,9 +349,7 @@
                                prot &= ~VM_PROT_WRITE;
 
                        if (prot & VM_PROT_WRITE) {
-                               uvm_unlock_pageq();
                                pg = uvm_loanbreak(pg);
-                               uvm_lock_pageq();
                                if (pg == NULL)
                                        continue; /* will re-fault */
                        }
@@ -365,14 +367,21 @@
                    pg->offset < umap->writeoff ||
                    pg->offset + PAGE_SIZE > umap->writeoff + umap->writelen);
                mask = rdonly ? ~VM_PROT_WRITE : VM_PROT_ALL;
-               pmap_enter(ufi->orig_map->pmap, va, VM_PAGE_TO_PHYS(pg),
-                   prot & mask, access_type & mask);
+               error = pmap_enter(ufi->orig_map->pmap, va, VM_PAGE_TO_PHYS(pg),
+                   prot & mask, PMAP_CANFAIL | (access_type & mask));
+               uvm_lock_pageq();
                uvm_pageactivate(pg);
-               pg->flags &= ~(PG_BUSY);
+               uvm_unlock_pageq();
+               pg->flags &= ~(PG_BUSY|PG_WANTED);
                UVM_PAGE_OWN(pg, NULL);
+               simple_unlock(&uobj->vmobjlock);
+               if (error) {
+                       UVMHIST_LOG(ubchist, "pmap_enter fail %d",
+                           error, 0, 0, 0);
+                       uvm_wait("ubc_pmfail");
+                       /* will refault */
+               }
        }
-       uvm_unlock_pageq();
-       simple_unlock(&uobj->vmobjlock);
        pmap_update(ufi->orig_map->pmap);
        return 0;
 }