svn commit: r234765 - in stable/9/sys: amd64/amd64 i386/conf kern

[Alan Cox]

Author: alc
Date: Sat Apr 28 18:03:57 2012
New Revision: 234765
URL: http://svn.freebsd.org/changeset/base/234765

Log:
  MFC r233097
    With the changes over the past year to how accesses to the page's dirty
    field are synchronized, there is no need for pmap_protect() to acquire
    the page queues lock unless it is going to access the pv lists.

Modified:
  stable/9/sys/amd64/amd64/pmap.c
Directory Properties:
  stable/9/sys/   (props changed)
  stable/9/sys/amd64/include/xen/   (props changed)
  stable/9/sys/boot/   (props changed)
  stable/9/sys/boot/i386/efi/   (props changed)
  stable/9/sys/boot/ia64/efi/   (props changed)
  stable/9/sys/boot/ia64/ski/   (props changed)
  stable/9/sys/boot/powerpc/boot1.chrp/   (props changed)
  stable/9/sys/boot/powerpc/ofw/   (props changed)
  stable/9/sys/cddl/contrib/opensolaris/   (props changed)
  stable/9/sys/conf/   (props changed)
  stable/9/sys/contrib/dev/acpica/   (props changed)
  stable/9/sys/contrib/octeon-sdk/   (props changed)
  stable/9/sys/contrib/pf/   (props changed)
  stable/9/sys/contrib/x86emu/   (props changed)
  stable/9/sys/fs/   (props changed)
  stable/9/sys/fs/ntfs/   (props changed)
  stable/9/sys/i386/conf/XENHVM   (props changed)
  stable/9/sys/kern/subr_witness.c   (props changed)

Modified: stable/9/sys/amd64/amd64/pmap.c
==============================================================================
--- stable/9/sys/amd64/amd64/pmap.c	Sat Apr 28 17:54:54 2012	(r234764)
+++ stable/9/sys/amd64/amd64/pmap.c	Sat Apr 28 18:03:57 2012	(r234765)
@@ -2893,6 +2893,7 @@ pmap_protect(pmap_t pmap, vm_offset_t sv
 	pd_entry_t ptpaddr, *pde;
 	pt_entry_t *pte;
 	int anychanged;
+	boolean_t pv_lists_locked;
 
 	if ((prot & VM_PROT_READ) == VM_PROT_NONE) {
 		pmap_remove(pmap, sva, eva);
@@ -2903,9 +2904,10 @@ pmap_protect(pmap_t pmap, vm_offset_t sv
 	    (VM_PROT_WRITE|VM_PROT_EXECUTE))
 		return;
 
+	pv_lists_locked = FALSE;
+resume:
 	anychanged = 0;
 
-	vm_page_lock_queues();
 	PMAP_LOCK(pmap);
 	for (; sva < eva; sva = va_next) {
 
@@ -2954,9 +2956,25 @@ pmap_protect(pmap_t pmap, vm_offset_t sv
 				if (pmap_protect_pde(pmap, pde, sva, prot))
 					anychanged = 1;
 				continue;
-			} else if (!pmap_demote_pde(pmap, pde, sva)) {
-				/* The large page mapping was destroyed. */
-				continue;
+			} else {
+				if (!pv_lists_locked) {
+					pv_lists_locked = TRUE;
+					if (!mtx_trylock(&vm_page_queue_mtx)) {
+						if (anychanged)
+							pmap_invalidate_all(
+							    pmap);
+						PMAP_UNLOCK(pmap);
+						vm_page_lock_queues();
+						goto resume;
+					}
+				}
+				if (!pmap_demote_pde(pmap, pde, sva)) {
+					/*
+					 * The large page mapping was
+					 * destroyed.
+					 */
+					continue;
+				}
 			}
 		}
 
@@ -2996,7 +3014,8 @@ retry:
 	}
 	if (anychanged)
 		pmap_invalidate_all(pmap);
-	vm_page_unlock_queues();
+	if (pv_lists_locked)
+		vm_page_unlock_queues();
 	PMAP_UNLOCK(pmap);
 }