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From: John Baldwin <jhb@FreeBSD.org>
Date: Wed, 20 Jun 2012 18:00:26 +0000 (UTC)
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Subject: svn commit: r237334 - head/sys/vm
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Author: jhb
Date: Wed Jun 20 18:00:26 2012
New Revision: 237334
URL: http://svn.freebsd.org/changeset/base/237334

Log:
  Move the per-thread deferred user map entries list into a private list
  in vm_map_process_deferred() which is then iterated to release map entries.
  This avoids having a nested vm map unlock operation called from the loop
  body attempt to recuse into vm_map_process_deferred().  This can happen if
  the vm_map_remove() triggers the OOM killer.
  
  Reviewed by:	alc, kib
  MFC after:	1 week

Modified:
  head/sys/vm/vm_map.c

Modified: head/sys/vm/vm_map.c
==============================================================================
--- head/sys/vm/vm_map.c	Wed Jun 20 17:52:21 2012	(r237333)
+++ head/sys/vm/vm_map.c	Wed Jun 20 18:00:26 2012	(r237334)
@@ -475,12 +475,14 @@ static void
 vm_map_process_deferred(void)
 {
 	struct thread *td;
-	vm_map_entry_t entry;
+	vm_map_entry_t entry, next;
 	vm_object_t object;
 
 	td = curthread;
-	while ((entry = td->td_map_def_user) != NULL) {
-		td->td_map_def_user = entry->next;
+	entry = td->td_map_def_user;
+	td->td_map_def_user = NULL;
+	while (entry != NULL) {
+		next = entry->next;
 		if ((entry->eflags & MAP_ENTRY_VN_WRITECNT) != 0) {
 			/*
 			 * Decrement the object's writemappings and
@@ -494,6 +496,7 @@ vm_map_process_deferred(void)
 			    entry->end);
 		}
 		vm_map_entry_deallocate(entry, FALSE);
+		entry = next;
 	}
 }