K 10
svn:author
V 3
alc
K 8
svn:date
V 27
2004-09-12T20:20:40.000000Z
K 7
svn:log
V 785
Use an atomic op to update the pte in pmap_protect().  This is to prevent
the loss of a page modified (PG_M) bit in a race between processors.

Quoting Tor:
	One scenario where the old code could cause a lost PG_M bit is a
	multithreaded linux program (or FreeBSD program using the
	linuxthreads port) where one thread was starting a subprocess.
	The thread doing fork() would call vmspace_fork(), which would then
	call vm_map_copy_entry() which would call pmap_protect() on an area
	possibly accessed by other threads.

Additionally, make the clearing of PG_M by pmap_protect() unconditional if
write permission is removed.  Previously, PG_M could persist on a read-only
unmanaged page.  That seems inconsistent and confusing.

In collaboration with: tegge@

MT5 candidate
PR: 61852

END