svn commit: r253191 - head/sys/vm

[Konstantin Belousov]

Author: kib
Date: Thu Jul 11 05:58:28 2013
New Revision: 253191
URL: http://svnweb.freebsd.org/changeset/base/253191

Log:
  The vm_fault() should not be allowed to proceed on the map entry which
  is being wired now.  The entry wired count is changed to non-zero in
  advance, before the map lock is dropped.  This makes the vm_fault() to
  perceive the entry as wired, and breaks the fragment which moves the
  wire count from the shadowed page, to the upper page, making the code
  unwiring non-wired page.
  
  On the other hand, the vm_fault() calls from vm_fault_wire() should be
  allowed to proceed, so only drain MAP_ENTRY_IN_TRANSITION from
  vm_fault() when wiring_thread is not current.
  
  Reported and tested by:	pho
  Reviewed by:	alc
  Sponsored by:	The FreeBSD Foundation
  MFC after:	2 weeks

Modified:
  head/sys/vm/vm_fault.c

Modified: head/sys/vm/vm_fault.c
==============================================================================
--- head/sys/vm/vm_fault.c	Thu Jul 11 05:55:08 2013	(r253190)
+++ head/sys/vm/vm_fault.c	Thu Jul 11 05:58:28 2013	(r253191)
@@ -280,6 +280,19 @@ RetryFault:;
 		    (u_long)vaddr);
 	}
 
+	if (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION &&
+	    fs.entry->wiring_thread != curthread) {
+		vm_map_unlock_read(fs.map);
+		vm_map_lock(fs.map);
+		if (vm_map_lookup_entry(fs.map, vaddr, &fs.entry) &&
+		    (fs.entry->eflags & MAP_ENTRY_IN_TRANSITION)) {
+			fs.entry->eflags |= MAP_ENTRY_NEEDS_WAKEUP;
+			vm_map_unlock_and_wait(fs.map, 0);
+		} else
+			vm_map_unlock(fs.map);
+		goto RetryFault;
+	}
+
 	/*
 	 * Make a reference to this object to prevent its disposal while we
 	 * are messing with it.  Once we have the reference, the map is free