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Re: double fault -> PAGE_KERNEL flagged memory

From: Mathieu Desnoyers <compudj at krystal dot dyndns dot org>
To: Tom Zanussi <zanussi at us dot ibm dot com>
Cc: "Stone, Joshua I" <joshua dot i dot stone at intel dot com>, michel dot dagenais at polymtl dot ca, systemtap at sources dot redhat dot com
Date: Tue, 22 Nov 2005 10:23:53 -0500
Subject: Re: double fault -> PAGE_KERNEL flagged memory
References: <CBDB88BFD06F7F408399DBCF8776B3DC05A8FB95@scsmsx403.amr.corp.intel.com> <20051122140021.GA3907@Krystal> <17283.13647.856527.25948@tut.ibm.com>

* Tom Zanussi (zanussi@us.ibm.com) wrote:
> It already is PAGE_KERNEL. 

You are right.

> The page faults you see with relayfs are
> vmalloc page faults i.e. minor faults that just update the kernel part
> of the current process's page table with the buffer pages.
> 

Generally speaking, what would happen if :

- A page fault handler has a trace point that logs an event in the RelayFS
  buffer.
- This exact write causes a (minor) page fault.

It may not happen often, but I think it would lead to a double fault. Is this
case possible ?


Mathieu


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Follow-Ups:
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References:
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  - From: Stone, Joshua I
- Re: double fault -> PAGE_KERNEL flagged memory
  - From: Mathieu Desnoyers
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