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Re: double fault

From: Mathieu Desnoyers <compudj at krystal dot dyndns dot org>
To: Martin Hunt <hunt at redhat dot com>
Cc: "Stone, Joshua I" <joshua dot i dot stone at intel dot com>, "systemtap at sources dot redhat dot com" <systemtap at sources dot redhat dot com>
Date: Wed, 23 Nov 2005 12:21:45 -0500
Subject: Re: double fault
References: <CBDB88BFD06F7F408399DBCF8776B3DC05A8FB95@scsmsx403.amr.corp.intel.com> <1132734576.4203.11.camel@monkey2>

* Martin Hunt (hunt@redhat.com) wrote:
> Changing the kprobe to other functions does not always trigger the bug.
> 
> The problem also has something to do with the size of the context array.
> Changing NR_CPUS to 128 (which makes the array really huge) was enough
> to cause the double fault to happen on all my RHEL machines (including
> x86_64) except for ones running under vmware. I changed the code to use
> vmalloc (we really want vmalloc_node() but RHEL4 doesn't have it) and
> all the crashes stopped on every machine.
> 

What are the flags used for the memory allocated by vmalloc ?

Did you try : 

- allocating the memory with kmalloc instead of vmalloc ?
- to see if there is a code path that goes from do_page_fault to sys_open ? I
  would be surprised about it, but we never know...

Mathieu

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References:
- double fault
  - From: Stone, Joshua I
- Re: double fault
  - From: Martin Hunt

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