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Date: Sat, 07 Sep 2013 19:23:33 -0700
From: Peter Grehan <grehan@freebsd.org>
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To: Justin Hibbits <jhibbits@freebsd.org>
Subject: Re: Kernel panic during page-out
References: <CAHSQbTCmr5ofovvAYXtrQP86JLsOinGePet57hT1437K03=GKA@mail.gmail.com>
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Hi Justin,

> I'm seeing a kernel panic on my G5, I think when it tries to page out to
> swap, with the message:
>
> Lock vm object not exclusively locked @ .../aim/mmu_oea64.c:1529
> backtrace:
> .kdb_backtrace+0x5c
> .vpanic+0x13c
> .panic+0x38
> .__rw_assert+0x184
> .moea64_is_modified+0x54
> .moea64_remove_all+0x78
> .vm_pageout_object_deactivate_pages+0x2e4
> .vm_daemon+0x358
> .fork_exit+0xdc
> .fork_trampoline+0x10
>
> This machine has 12GiB RAM, running r254922.

  This is the same panic I saw on the g5 imac when I only had 512MB of 
RAM - 'twas much too easy to reproduce.

  The fix is

moea64_is_modified
  ...
-	VM_OBJECT_ASSERT_WLOCKED(m->object);
+	VM_OBJECT_ASSERT_LOCKED(m->object);

  This is consistent with locking higher up in the call chain. Apologies 
for not submitting that when I found it (and discussed it with Nathan).


later,

Peter.