From: mpi <mpi@openbsd.org>
Date: Tue, 5 Oct 2021 15:37:21 +0000 (+0000)
Subject: Unref/free amaps before grabbing the KERNEL_LOCK().
X-Git-Url: http://artulab.com/gitweb/?a=commitdiff_plain;h=2a71da199878e7fa35aa125dc803f5d67665f3a9;p=openbsd

Unref/free amaps before grabbing the KERNEL_LOCK().

This is possible now that amaps & anons are protected by a per-map rwlock.

Tested by many as part of a bigger diff.

ok kettenis@
---

diff --git a/sys/uvm/uvm_map.c b/sys/uvm/uvm_map.c
index 3c4e8851f4b..e36c761b425 100644
--- a/sys/uvm/uvm_map.c
+++ b/sys/uvm/uvm_map.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_map.c,v 1.277 2021/06/17 16:10:39 mpi Exp $	*/
+/*	$OpenBSD: uvm_map.c,v 1.278 2021/10/05 15:37:21 mpi Exp $	*/
 /*	$NetBSD: uvm_map.c,v 1.86 2000/11/27 08:40:03 chs Exp $	*/
 
 /*
@@ -1570,9 +1570,15 @@ uvm_unmap_detach(struct uvm_map_deadq *deadq, int flags)
 	int waitok = flags & UVM_PLA_WAITOK;
 
 	TAILQ_FOREACH_SAFE(entry, deadq, dfree.deadq, tmp) {
+		/* Drop reference to amap, if we've got one. */
+		if (entry->aref.ar_amap)
+			amap_unref(entry->aref.ar_amap,
+			    entry->aref.ar_pageoff,
+			    atop(entry->end - entry->start),
+			    flags & AMAP_REFALL);
+
 		/* Skip entries for which we have to grab the kernel lock. */
-		if (entry->aref.ar_amap || UVM_ET_ISSUBMAP(entry) ||
-		    UVM_ET_ISOBJ(entry))
+		if (UVM_ET_ISSUBMAP(entry) || UVM_ET_ISOBJ(entry))
 			continue;
 
 		TAILQ_REMOVE(deadq, entry, dfree.deadq);
@@ -1586,13 +1592,6 @@ uvm_unmap_detach(struct uvm_map_deadq *deadq, int flags)
 	while ((entry = TAILQ_FIRST(deadq)) != NULL) {
 		if (waitok)
 			uvm_pause();
-		/* Drop reference to amap, if we've got one. */
-		if (entry->aref.ar_amap)
-			amap_unref(entry->aref.ar_amap,
-			    entry->aref.ar_pageoff,
-			    atop(entry->end - entry->start),
-			    flags & AMAP_REFALL);
-
 		/* Drop reference to our backing object, if we've got one. */
 		if (UVM_ET_ISSUBMAP(entry)) {
 			/* ... unlikely to happen, but play it safe */