[haiku-bugs] Re: [Haiku] #8345: PANIC: ASSERT FAILED ... x86/paging/pae/x86VMTranslationMapPAE.cpp:231
- From: "bonefish" <trac@xxxxxxxxxxxx>
- Date: Tue, 10 Jul 2012 05:57:41 -0000
#8345: PANIC: ASSERT FAILED ... x86/paging/pae/x86VMTranslationMapPAE.cpp:231
-----------------------------+------------------------------------
Reporter: kallisti5 | Owner: bonefish
Type: bug | Status: assigned
Priority: critical | Milestone: R1/alpha4
Component: System/Kernel | Version: R1/Development
Resolution: | Keywords: x86VMTranslationMapPAE
Blocked By: | Blocking:
Has a Patch: 0 | Platform: x86
-----------------------------+------------------------------------
Old description:
> I've seen this a few times now randomly after doing lots of compiling
> under Haiku GCC4...
>
> {{{
> PANIC: ASSERT FAILED ... x86/paging/pae/x86VMTranslationMapPAE.cpp:231
>
> http://cgit.haiku-
> os.org/haiku/tree/src/system/kernel/arch/x86/paging/pae/X86VMTranslationMapPAE.cpp?id=hrev43765#n229
>
> (*entry & 0x0000000000000001LL) == 0; virtual address: 0x7ffef00,
> existing pte: 0xfffffffffffffff
> }}}
New description:
I've seen this a few times now randomly after doing lots of compiling
under Haiku GCC4...
{{{
PANIC: ASSERT FAILED ... x86/paging/pae/x86VMTranslationMapPAE.cpp:231
(*entry & 0x0000000000000001LL) == 0; virtual address: 0x7ffef000,
existing pte: 0xffffffffffffffff
}}}
http://cgit.haiku-
os.org/haiku/tree/src/system/kernel/arch/x86/paging/pae/X86VMTranslationMapPAE.cpp?id=hrev43765#n229
--
Comment (by bonefish):
I just noticed I hadn't commented on that one yet. While the issue itself
isn't all that critical the underlying cause possibly is. The `Map()`
method of the translation map maps a virtual address to a physical page.
That is achieved by writing a respectively composed value (the physical
page address mixed with flags for the access permissions and other stuff)
into a respective page table entry (PTE). It is expected that when `Map()`
is invoked that the virtual address is not already mapped to a physical
page. That's what the assert checks (the "page present" flag of the PTE).
Since the new value is written to the PTE, it will be OK afterwards -- the
panic is continuable -- but that the previous value got there is
worrisome. Even more so since in this case the value is `~0`, something
never written by the paging code. So someone else wrote into that page
table. Not a comforting thought.
Michael mentioned that he thinks that this happens when nearly exhausting
physical pages. When it happens next time, please run a `page_stats` so we
can verify the theory. Also, it would be interesting in what situation the
assert was triggered. Like how long the machine ran and what you did
before. Obviously a reproducible test case would be perfect.
--
Ticket URL: <http://dev.haiku-os.org/ticket/8345#comment:8>
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