Date: Mon, 9 Nov 1998 15:56:29 -0500 (EST) From: Luoqi Chen <luoqi@watermarkgroup.com> To: dg@root.com, wollman@khavrinen.lcs.mit.edu Cc: current@FreeBSD.ORG, eivind@yes.no, jfieber@indiana.edu Subject: Re: The infamous dying daemons bug Message-ID: <199811092056.PAA22043@lor.watermarkgroup.com>
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> Totally unrelated to the problem. It seems, so far as I was able to
> characterize, to happen to daemons which are *swapped out* at the time
> of the memory shortage. If it's active enough to still be in core, it
> doesn't get spammed.
>
I went through swap_pager.c today and found a problem that could potentially
have bad consequences. It's a comparison between page index in the swap pager
and the size of the vm object, since a shadowed object may have a non-zero
paging offset with respect to the swap pager, the comparison should have taken
the offset into account. This piece of code has been there since '95, so
I can't say if this was responsible for the daemon dying problem.
-lq
Index: swap_pager.c
===================================================================
RCS file: /home/ncvs/src/sys/vm/swap_pager.c,v
retrieving revision 1.103
diff -u -r1.103 swap_pager.c
--- swap_pager.c 1998/10/31 15:31:28 1.103
+++ swap_pager.c 1998/11/09 11:02:54
@@ -349,7 +349,7 @@
*valid = 0;
ix = pindex / SWB_NPAGES;
if ((ix >= object->un_pager.swp.swp_nblocks) ||
- (pindex >= object->size)) {
+ (pindex >= object->size + OFF_TO_IDX(object->paging_offset))) {
return (FALSE);
}
swb = &object->un_pager.swp.swp_blocks[ix];
@@ -1227,8 +1227,8 @@
* intent of this code is to allocate small chunks for
* small objects)
*/
- if ((off == 0) && ((fidx + ntoget) > object->size)) {
- ntoget = object->size - fidx;
+ if ((off == 0) && ((fidx + ntoget) > object->size + paging_pindex)) {
+ ntoget = object->size + paging_pindex - fidx;
}
retrygetspace:
if (!swap_pager_full && ntoget > 1 &&
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