svn commit: r252496 - stable/9/sys/dev/drm2/i915

[Konstantin Belousov]

Author: kib
Date: Tue Jul  2 04:42:32 2013
New Revision: 252496
URL: http://svnweb.freebsd.org/changeset/base/252496

Log:
  MFC r251960:
  Since the gem pagefault handler relocks the vm object lock, other
  thread might fault on the same GTT offset meantime and instantiate the
  mapping.  Recheck that the mgt device object still does not have a
  page at the current offset after relocking, and return a possibly
  installed page.

Modified:
  stable/9/sys/dev/drm2/i915/i915_gem.c
Directory Properties:
  stable/9/sys/   (props changed)
  stable/9/sys/dev/   (props changed)

Modified: stable/9/sys/dev/drm2/i915/i915_gem.c
==============================================================================
--- stable/9/sys/dev/drm2/i915/i915_gem.c	Tue Jul  2 04:27:16 2013	(r252495)
+++ stable/9/sys/dev/drm2/i915/i915_gem.c	Tue Jul  2 04:42:32 2013	(r252496)
@@ -1371,6 +1371,23 @@ unlocked_vmobj:
 	} else
 		DRM_LOCK(dev);
 
+	/*
+	 * Since the object lock was dropped, other thread might have
+	 * faulted on the same GTT address and instantiated the
+	 * mapping for the page.  Recheck.
+	 */
+	VM_OBJECT_LOCK(vm_obj);
+	m = vm_page_lookup(vm_obj, OFF_TO_IDX(offset));
+	if (m != NULL) {
+		if ((m->flags & VPO_BUSY) != 0) {
+			DRM_UNLOCK(dev);
+			vm_page_sleep(m, "915pee");
+			goto retry;
+		}
+		goto have_page;
+	} else
+		VM_OBJECT_UNLOCK(vm_obj);
+
 	/* Now bind it into the GTT if needed */
 	if (!obj->map_and_fenceable) {
 		ret = i915_gem_object_unbind(obj);
@@ -1424,8 +1441,9 @@ unlocked_vmobj:
 		goto retry;
 	}
 	m->valid = VM_PAGE_BITS_ALL;
-	*mres = m;
 	vm_page_insert(m, vm_obj, OFF_TO_IDX(offset));
+have_page:
+	*mres = m;
 	vm_page_busy(m);
 
 	CTR4(KTR_DRM, "fault %p %jx %x phys %x", gem_obj, offset, prot,