> Date: Sun, 23 Dec 2018 21:20:11 +0100 (CET)
> From: Mark Kettenis <mark.kette...@xs4all.nl>
>
> > Date: Sun, 23 Dec 2018 19:35:02 +0100 (CET)
> > From: Mark Kettenis <mark.kette...@xs4all.nl>
> >
> > > Date: Sun, 23 Dec 2018 12:26:17 +0100 (CET)
> > > From: Mark Kettenis <mark.kette...@xs4all.nl>
> > >
> > > That's a very good find. I think there still is a potential race in
> > > your diff on MP systems since you save the bits before removing the
> > > PTE from the has tables. I'll see if I can come up with a better diff.
> >
> > So here is the diff I propose instead. This zaps the PTE before
> > unlinking. At that point the PTED_VA_MANAGED_M flag is still set so
> > the MOD/REF accounting will happen. A process running on the other
> > CPU can't put the PTE back into the hash as we still hold the lock on
> > the pmap.
> >
> > Bootstrapping clang with this diff, and things are still running even
> > though I've hit swap. I'll give this a spin on an MP machine as well.
>
> I fear sombody else needs to test on an MP machine as my dual G4
> doesn't boot anymore :(.
And for those only on ppc@, here is the diff again.
Please test.
Index: arch/powerpc/powerpc/pmap.c
===================================================================
RCS file: /cvs/src/sys/arch/powerpc/powerpc/pmap.c,v
retrieving revision 1.168
diff -u -p -r1.168 pmap.c
--- arch/powerpc/powerpc/pmap.c 22 Oct 2018 17:31:25 -0000 1.168
+++ arch/powerpc/powerpc/pmap.c 23 Dec 2018 18:25:32 -0000
@@ -2067,7 +2067,9 @@ void
pmap_page_protect(struct vm_page *pg, vm_prot_t prot)
{
struct pte_desc *pted;
+ void *pte;
pmap_t pm;
+ int s;
if (prot == PROT_NONE) {
mtx_enter(&pg->mdpage.pv_mtx);
@@ -2097,6 +2099,11 @@ pmap_page_protect(struct vm_page *pg, vm
mtx_enter(&pg->mdpage.pv_mtx);
continue;
}
+
+ PMAP_HASH_LOCK(s);
+ if ((pte = pmap_ptedinhash(pted)) != NULL)
+ pte_zap(pte, pted);
+ PMAP_HASH_UNLOCK(s);
pted->pted_va &= ~PTED_VA_MANAGED_M;
LIST_REMOVE(pted, pted_pv_list);
