[src/trunk]: src/sys/uvm - uvm_unmap_remove(): need to call pmap_update() wit...

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

details:   https://anonhg.NetBSD.org/src/rev/b1a03dae0bf5
branches:  trunk
changeset: 968322:b1a03dae0bf5
user:      ad <ad%NetBSD.org@localhost>
date:      Sun Jan 12 17:46:55 2020 +0000

description:
- uvm_unmap_remove(): need to call pmap_update() with the object still
  locked, otherwise the page could gain a new identity and still be visible
  via a stale mapping.

- Adjust reference counts with atomics.

diffstat:

 sys/uvm/uvm_map.c |  51 ++++++++++++++++++++++-----------------------------
 sys/uvm/uvm_map.h |   4 ++--
 2 files changed, 24 insertions(+), 31 deletions(-)

diffs (136 lines):

diff -r cc94a6c19b22 -r b1a03dae0bf5 sys/uvm/uvm_map.c
--- a/sys/uvm/uvm_map.c Sun Jan 12 16:11:51 2020 +0000
+++ b/sys/uvm/uvm_map.c Sun Jan 12 17:46:55 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_map.c,v 1.370 2020/01/05 15:57:15 para Exp $       */
+/*     $NetBSD: uvm_map.c,v 1.371 2020/01/12 17:46:55 ad Exp $ */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -66,7 +66,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_map.c,v 1.370 2020/01/05 15:57:15 para Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_map.c,v 1.371 2020/01/12 17:46:55 ad Exp $");
 
 #include "opt_ddb.h"
 #include "opt_pax.h"
@@ -2240,7 +2240,7 @@
        }
 
        /*
-        * Save the free space hint
+        * save the free space hint
         */
 
        if (map->first_free != &map->header && map->first_free->start >= start)
@@ -2314,6 +2314,18 @@
 
                        uvm_map_lock_entry(entry);
                        pmap_remove(map->pmap, entry->start, entry->end);
+
+                       /*
+                        * note: if map is dying, leave pmap_update() for
+                        * pmap_destroy(), which will be called later.
+                        */
+
+                       if ((map->flags & VM_MAP_DYING) == 0) {
+                               pmap_update(vm_map_pmap(map));
+                       } else {
+                               KASSERT(vm_map_pmap(map) != pmap_kernel());
+                       }
+
                        uvm_map_unlock_entry(entry);
                }
 
@@ -2358,16 +2370,6 @@
                entry = next;
        }
 
-       /*
-        * Note: if map is dying, leave pmap_update() for pmap_destroy(),
-        * which will be called later.
-        */
-       if ((map->flags & VM_MAP_DYING) == 0) {
-               pmap_update(vm_map_pmap(map));
-       } else {
-               KASSERT(vm_map_pmap(map) != pmap_kernel());
-       }
-
        uvm_map_check(map, "unmap_remove leave");
 
        /*
@@ -4254,14 +4256,10 @@
 void
 uvmspace_addref(struct vmspace *vm)
 {
-       struct vm_map *map = &vm->vm_map;
-
-       KASSERT((map->flags & VM_MAP_DYING) == 0);
-
-       mutex_enter(&map->misc_lock);
+
+       KASSERT((vm->vm_map.flags & VM_MAP_DYING) == 0);
        KASSERT(vm->vm_refcnt > 0);
-       vm->vm_refcnt++;
-       mutex_exit(&map->misc_lock);
+       atomic_inc_uint(&vm->vm_refcnt);
 }
 
 /*
@@ -4273,16 +4271,12 @@
 {
        struct vm_map_entry *dead_entries;
        struct vm_map *map = &vm->vm_map;
-       int n;
 
        UVMHIST_FUNC("uvmspace_free"); UVMHIST_CALLED(maphist);
 
        UVMHIST_LOG(maphist,"(vm=%#jx) ref=%jd", (uintptr_t)vm, vm->vm_refcnt,
            0, 0);
-       mutex_enter(&map->misc_lock);
-       n = --vm->vm_refcnt;
-       mutex_exit(&map->misc_lock);
-       if (n > 0)
+       if (atomic_dec_uint_nv(&vm->vm_refcnt) > 0)
                return;
 
        /*
@@ -4777,15 +4771,14 @@
 /*
  * uvm_map_reference: add reference to a map
  *
- * => map need not be locked (we use misc_lock).
+ * => map need not be locked
  */
 
 void
 uvm_map_reference(struct vm_map *map)
 {
-       mutex_enter(&map->misc_lock);
-       map->ref_count++;
-       mutex_exit(&map->misc_lock);
+
+       atomic_inc_uint(&map->ref_count);
 }
 
 void
diff -r cc94a6c19b22 -r b1a03dae0bf5 sys/uvm/uvm_map.h
--- a/sys/uvm/uvm_map.h Sun Jan 12 16:11:51 2020 +0000
+++ b/sys/uvm/uvm_map.h Sun Jan 12 17:46:55 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: uvm_map.h,v 1.76 2020/01/05 15:57:15 para Exp $        */
+/*     $NetBSD: uvm_map.h,v 1.77 2020/01/12 17:46:55 ad Exp $  */
 
 /*
  * Copyright (c) 1997 Charles D. Cranor and Washington University.
@@ -209,7 +209,7 @@
        struct pmap *           pmap;           /* Physical map */
        krwlock_t               lock;           /* Non-intrsafe lock */
        struct lwp *            busy;           /* LWP holding map busy */
-       kmutex_t                misc_lock;      /* Lock for ref_count, cv */
+       kmutex_t                misc_lock;      /* Lock for cv, busy */
        kcondvar_t              cv;             /* For signalling */
        int                     flags;          /* flags */
        struct rb_tree          rb_tree;        /* Tree for entries */