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Date: Thu, 03 Jun 2010 08:56:06 +0200
From: Jan Kiszka <jan.kiszka@domain.hid>
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Subject: Re: [Xenomai-core] [RFC] Break out of endless user space loops
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To: Philippe Gerum <rpm@xenomai.org>
Cc: xenomai-core <xenomai@xenomai.org>, Tschaeche IT-Services <services@domain.hid>

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Philippe Gerum wrote:
> On Wed, 2010-06-02 at 19:19 +0200, Jan Kiszka wrote:
>> Hi all,
>>
>> here is the first apparently working prototype for getting hold of
>> endless user space loops in RT threads. A simple test case of mine now=

>> receive a SIGDEBUG even if it does "while (1);".
>>
>> The design follows Gilles' suggestion to force a SEGV on victim thread=

>> but restore the patched PC before migrating the thread after this faul=
t.
>> The only drawback of this approach: We need to keep track of the
>> preempted register set at I-pipe level. I basically replicated what
>> Linux does these days as well and exported it as ipipe_get_irq_regs()
>> (the second patch).
>>
>> This is an x86-64-only draft which clearly needs more love. I'm open f=
or
>> suggestions of different abstractions wherever you see a need.
>=20
> What if you have no MMU ?

Then you either have an MPU detecting NULL pointer accesses or you can
actually redirect the PC to some kernel function containing some other
invalid, exception-raising instruction.

Jan


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