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[src/netbsd-2-0]: src/sys/uvm Pull up following revision(s) (requested by chs...
details: https://anonhg.NetBSD.org/src/rev/2328945fca66
branches: netbsd-2-0
changeset: 564941:2328945fca66
user: tron <tron%NetBSD.org@localhost>
date: Fri Jan 27 22:21:01 2006 +0000
description:
Pull up following revision(s) (requested by chs in ticket #10230):
sys/uvm/uvm_amap.c: revision 1.66 via patch
in amap_cow_now(), handle the case where we have to sleep and some of the
already-copied pages are paged out. anons that have already been copied
will have refcount == 1, whereas anons that still need to be copied will
have refcount > 1. fixes PR 25392, PR 30257, PR 31924.
diffstat:
sys/uvm/uvm_amap.c | 151 ++++++++++++++++++++++++++++------------------------
1 files changed, 80 insertions(+), 71 deletions(-)
diffs (194 lines):
diff -r c0c42ba233c8 -r 2328945fca66 sys/uvm/uvm_amap.c
--- a/sys/uvm/uvm_amap.c Thu Jan 19 21:38:27 2006 +0000
+++ b/sys/uvm/uvm_amap.c Fri Jan 27 22:21:01 2006 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: uvm_amap.c,v 1.53.2.1 2005/03/16 12:11:08 tron Exp $ */
+/* $NetBSD: uvm_amap.c,v 1.53.2.2 2006/01/27 22:21:01 tron Exp $ */
/*
*
@@ -42,7 +42,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: uvm_amap.c,v 1.53.2.1 2005/03/16 12:11:08 tron Exp $");
+__KERNEL_RCSID(0, "$NetBSD: uvm_amap.c,v 1.53.2.2 2006/01/27 22:21:01 tron Exp $");
#undef UVM_AMAP_INLINE /* enable/disable amap inlines */
@@ -920,7 +920,6 @@
ReStart:
amap_lock(amap);
-
for (lcv = 0 ; lcv < amap->am_nused ; lcv++) {
/*
@@ -930,89 +929,99 @@
slot = amap->am_slots[lcv];
anon = amap->am_anon[slot];
simple_lock(&anon->an_lock);
- pg = anon->u.an_page;
/*
- * page must be resident since parent is wired
+ * If the anon has only one ref, we must have already copied it.
+ * This can happen if we needed to sleep waiting for memory
+ * in a previous run through this loop. The new page might
+ * even have been paged out, since the new page is not wired.
*/
- if (pg == NULL)
- panic("amap_cow_now: non-resident wired page in anon %p",
- anon);
+ if (anon->an_ref == 1) {
+ KASSERT(anon->u.an_page != NULL ||
+ anon->an_swslot != 0);
+ simple_unlock(&anon->an_lock);
+ continue;
+ }
+
+ /*
+ * The old page must be resident since the parent is wired.
+ */
+
+ pg = anon->u.an_page;
+ KASSERT(pg != NULL);
+ KASSERT(pg->wire_count > 0);
/*
- * if the anon ref count is one and the page is not loaned,
- * then we are safe (the child has exclusive access to the
- * page). if the page is loaned, then it must already be
- * mapped read-only.
- *
- * we only need to get involved when these are not true.
- * [note: if loan_count == 0, then the anon must own the page]
+ * If the page is loaned then it must already be mapped
+ * read-only and we don't need to copy it.
+ */
+
+ if (pg->loan_count != 0) {
+ simple_unlock(&anon->an_lock);
+ continue;
+ }
+ KASSERT(pg->uanon == anon && pg->uobject == NULL);
+
+ /*
+ * if the page is busy then we have to unlock, wait for
+ * it and then restart.
*/
- if (anon->an_ref > 1 && pg->loan_count == 0) {
+ if (pg->flags & PG_BUSY) {
+ pg->flags |= PG_WANTED;
+ amap_unlock(amap);
+ UVM_UNLOCK_AND_WAIT(pg, &anon->an_lock, FALSE,
+ "cownow", 0);
+ goto ReStart;
+ }
- /*
- * if the page is busy then we have to unlock, wait for
- * it and then restart.
- */
- if (pg->flags & PG_BUSY) {
- pg->flags |= PG_WANTED;
- amap_unlock(amap);
- UVM_UNLOCK_AND_WAIT(pg, &anon->an_lock, FALSE,
- "cownow", 0);
- goto ReStart;
- }
+ /*
+ * ok, time to do a copy-on-write to a new anon
+ */
+
+ nanon = uvm_analloc();
+ if (nanon) {
+ npg = uvm_pagealloc(NULL, 0, nanon, 0);
+ } else
+ npg = NULL; /* XXX: quiet gcc warning */
+ if (nanon == NULL || npg == NULL) {
/*
- * ok, time to do a copy-on-write to a new anon
- */
- nanon = uvm_analloc();
- if (nanon) {
- /* nanon is locked! */
- npg = uvm_pagealloc(NULL, 0, nanon, 0);
- } else
- npg = NULL; /* XXX: quiet gcc warning */
-
- if (nanon == NULL || npg == NULL) {
- /* out of memory */
- /*
- * XXXCDC: we should cause fork to fail, but
- * we can't ...
- */
- if (nanon) {
- nanon->an_ref--;
- simple_unlock(&nanon->an_lock);
- uvm_anfree(nanon);
- }
- simple_unlock(&anon->an_lock);
- amap_unlock(amap);
- uvm_wait("cownowpage");
- goto ReStart;
- }
-
- /*
- * got it... now we can copy the data and replace anon
- * with our new one...
+ * XXXCDC: we should cause fork to fail, but we can't.
*/
- uvm_pagecopy(pg, npg); /* old -> new */
- anon->an_ref--; /* can't drop to zero */
- amap->am_anon[slot] = nanon; /* replace */
+ if (nanon) {
+ nanon->an_ref--;
+ simple_unlock(&nanon->an_lock);
+ uvm_anfree(nanon);
+ }
+ simple_unlock(&anon->an_lock);
+ amap_unlock(amap);
+ uvm_wait("cownowpage");
+ goto ReStart;
+ }
+
+ /*
+ * got it... now we can copy the data and replace anon
+ * with our new one...
+ */
- /*
- * drop PG_BUSY on new page ... since we have had it's
- * owner locked the whole time it can't be
- * PG_RELEASED | PG_WANTED.
- */
+ uvm_pagecopy(pg, npg); /* old -> new */
+ anon->an_ref--; /* can't drop to zero */
+ amap->am_anon[slot] = nanon; /* replace */
- uvm_lock_pageq();
- uvm_pageactivate(npg);
- uvm_unlock_pageq();
- npg->flags &= ~(PG_BUSY|PG_FAKE);
- UVM_PAGE_OWN(npg, NULL);
- simple_unlock(&nanon->an_lock);
- }
+ /*
+ * drop PG_BUSY on new page ... since we have had its owner
+ * locked the whole time it can't be PG_RELEASED or PG_WANTED.
+ */
+
+ uvm_lock_pageq();
+ uvm_pageactivate(npg);
+ uvm_unlock_pageq();
+ npg->flags &= ~(PG_BUSY|PG_FAKE);
+ UVM_PAGE_OWN(npg, NULL);
+ simple_unlock(&nanon->an_lock);
simple_unlock(&anon->an_lock);
}
amap_unlock(amap);
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