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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Thu, 20 May 2010 08:51:01 +0000 (UTC)
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Subject: svn commit: r208340 - head/sys/vm
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Author: kib
Date: Thu May 20 08:51:01 2010
New Revision: 208340
URL: http://svn.freebsd.org/changeset/base/208340

Log:
  When waiting for the busy page, do not unlock the object unless unlock
  cannot be avoided.
  
  Reviewed by:	alc
  MFC after:	1 week

Modified:
  head/sys/vm/vm_fault.c

Modified: head/sys/vm/vm_fault.c
==============================================================================
--- head/sys/vm/vm_fault.c	Thu May 20 08:43:31 2010	(r208339)
+++ head/sys/vm/vm_fault.c	Thu May 20 08:51:01 2010	(r208340)
@@ -340,9 +340,13 @@ RetryFault:;
 				vm_page_flag_set(fs.m, PG_REFERENCED);
 				vm_page_unlock_queues();
 				vm_page_unlock(fs.m);
-				VM_OBJECT_UNLOCK(fs.object);
 				if (fs.object != fs.first_object) {
-					VM_OBJECT_LOCK(fs.first_object);
+					if (!VM_OBJECT_TRYLOCK(
+					    fs.first_object)) {
+						VM_OBJECT_UNLOCK(fs.object);
+						VM_OBJECT_LOCK(fs.first_object);
+						VM_OBJECT_LOCK(fs.object);
+					}
 					vm_page_lock(fs.first_m);
 					vm_page_free(fs.first_m);
 					vm_page_unlock(fs.first_m);
@@ -351,7 +355,6 @@ RetryFault:;
 					fs.first_m = NULL;
 				}
 				unlock_map(&fs);
-				VM_OBJECT_LOCK(fs.object);
 				if (fs.m == vm_page_lookup(fs.object,
 				    fs.pindex)) {
 					vm_page_sleep_if_busy(fs.m, TRUE,