From mboxrd@z Thu Jan  1 00:00:00 1970
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Date: Thu, 29 Jan 2009 16:00:47 +0000
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
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Subject: Re: [Xenomai-help] interrupt service routine issue
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To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: "xenomai@xenomai.org" <xenomai@xenomai.org>

Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> stefano.franzoni@domain.hid wrote:
>>> Thanks Gilles,
>>>
>>> with your suggestion, setting the special mode bit T_WARNSW for the
>>> incriminated task, we found two critical functions that caused switches to
>>> secondary mode.
>>>
>>> I report them for documentation:
>>>
>>> 1. We used mmap function used to map a file into memory. The access to the
>>> memory caused sometimes the switch to secondary mode.
>> damn, this should not happen, we use mlockall and some additional tricks
>> in the I-pipe patch to avoid that.
> 
> Mmmh, I don't think we can cure (/wrt RT) access to memory mapped files.
> That's just the same no-go for RT threads as other Linux I/O.

Well, normally, with mlockall, if you call mmap, the whole file is
loaded in memory. Of course, if there are "holes" in your file, a write
to the file will cause a fault.

-- 
                                                 Gilles.