From: mpi <mpi@openbsd.org>
Date: Thu, 10 Mar 2022 10:46:56 +0000 (+0000)
Subject: Do not clear the PG_BUSY flag before passing the anon to uvm_anon_release().
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=1340df41e0c476cd0cf3ce3ec2af61bd95845302;p=openbsd

Do not clear the PG_BUSY flag before passing the anon to uvm_anon_release().

Should prevent a KASSERT() from tiggering when freeing an anon after swaping-out
its memory.

This code path has been broken since at least January 2021 and is apparently not
so easy to trigger.

Found the hard way by sthen@

ok kettenis@, kn@
---

diff --git a/sys/uvm/uvm_page.c b/sys/uvm/uvm_page.c
index df40cd97395..57b7a52b426 100644
--- a/sys/uvm/uvm_page.c
+++ b/sys/uvm/uvm_page.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_page.c,v 1.161 2022/01/19 02:08:24 mpi Exp $	*/
+/*	$OpenBSD: uvm_page.c,v 1.162 2022/03/10 10:46:56 mpi Exp $	*/
 /*	$NetBSD: uvm_page.c,v 1.44 2000/11/27 08:40:04 chs Exp $	*/
 
 /*
@@ -1086,8 +1086,6 @@ uvm_page_unbusy(struct vm_page **pgs, int npgs)
 				uvm_pagefree(pg);
 				uvm_unlock_pageq();
 			} else {
-				atomic_clearbits_int(&pg->pg_flags, PG_BUSY);
-				UVM_PAGE_OWN(pg, NULL);
 				rw_enter(pg->uanon->an_lock, RW_WRITE);
 				uvm_anon_release(pg->uanon);
 			}