NetBSD Problem Report #55325

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Date: Sun, 31 May 2020 11:22:24 +0000 (UTC)
From: rokuyama.rk@gmail.com
Reply-To: rokuyama.rk@gmail.com
To: gnats-bugs@NetBSD.org
Subject: oea/pmap: inconsistency in usage of two PVO pools
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>Number:         55325
>Category:       port-powerpc
>Synopsis:       oea/pmap: inconsistency in usage of two PVO pools
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    port-powerpc-maintainer
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sun May 31 11:25:00 +0000 2020
>Closed-Date:    Wed Jul 07 00:28:39 +0000 2021
>Last-Modified:  Wed Jul 07 00:28:39 +0000 2021
>Originator:     Rin Okuyama
>Release:        9.99.64
>Organization:
Department of Physics, Meiji University
>Environment:
NetBSD macmini 9.99.64 NetBSD 9.99.64 (GENERIC) #65: Sun May 31 01:11:41 JST 2020  rin@latipes:/usr/src/sys/arch/macppc/compile/GENERIC macppc
>Description:
In powerpc/oea/pmap.c, there are two pools of PVO:
- pmap_upvo_pool for PVO entries for unmanaged pages
- pmap_mpvo_pool for PVO entries for managed pages

At the moment, we determine to which pool freed PVO is put back by
PVO_MANAGED flag. However, this is *wrong* when PVO is obtained by
pmap_pvo_reclaim(). That is, PVO for unmanaged pages can be reclaimed
from pool for managed, and vice versa.
>How-To-Repeat:
Enable DIAGNOSTIC, and put a system in heavy memory pressure, like

$ cd /usr/pkgsrc/devel/gcc10 && make MAKE_JOBS=2

Then, the system crashes for a while as:

panic: pr_phinpage_check: [pmap_upvopl] item 0xf619c0 poolid 36 != 1
>Fix:
Although I'm not sure whether this is a correct fix or not, but this
patch seems to fix a problem:

http://www.netbsd.org/~rin/oea_pmap_20200531.patch

Here, I introduced a new flag that represents from which pool PVO is
obtained:

#define PVO_POOL_MANAGED        0x0080
#define PVO_POOL_MANAGED_P(pvo) ((pvo)->pvo_vaddr & PVO_POOL_MANAGED)

Then, use this flag instead of PVO_MANAGED to determine to which pool
we should pool_put(9) into.

Alternatively, we can reclaim PVO from the same pool in
pmap_pvo_reclaim(). However, this attempt fails for me, by ended up in:

panic: pmap_pvo_enter: failed

>Release-Note:

>Audit-Trail:
From: "Martin Husemann" <martin@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/55325 CVS commit: src/sys/arch/powerpc/oea
Date: Sun, 27 Jun 2021 12:26:33 +0000

 Module Name:	src
 Committed By:	martin
 Date:		Sun Jun 27 12:26:33 UTC 2021

 Modified Files:
 	src/sys/arch/powerpc/oea: pmap.c

 Log Message:
 PR 55325: unify both pvo pools (for managed and unmanaged pages).
 Analyzis by rin, fix suggested by chs.


 To generate a diff of this commit:
 cvs rdiff -u -r1.105 -r1.106 src/sys/arch/powerpc/oea/pmap.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

From: Havard Eidnes <he@NetBSD.org>
To: gnats-bugs@netbsd.org, rokuyama.rk@gmail.com
Cc: port-powerpc-maintainer@netbsd.org
Subject: Re: port-powerpc/55325: oea/pmap: inconsistency in usage of two
 PVO pools
Date: Wed, 07 Jul 2021 00:01:34 +0200 (CEST)

 Hi,

 after the commit of src/sys/arch/powerpc/oea/pmap.c mentioned in
 this PR, I have spun up my dual-CPU G4 again which earlier fell
 victim to this problem, and this time it (unsurprisingly, perhaps)
 no longer fails with this error.

 In fact, it managed to complete a full build of wip/rust using both
 CPUs, and my trust in the system's stability for the upcoming
 release has solidified.

 So ... as far as I'm concerned this PR can now be closed.

 Regards,

 - Havard

State-Changed-From-To: open->closed
State-Changed-By: dholland@NetBSD.org
State-Changed-When: Wed, 07 Jul 2021 00:28:39 +0000
State-Changed-Why:
confirmed fixed, thanks


>Unformatted:

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