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Date:      Mon, 27 May 2013 15:17:46 +0300
From:      Andriy Gapon <avg@FreeBSD.org>
To:        Orit Moskovich <oritm@mellanox.com>
Cc:        Konstantin Belousov <kostikbel@gmail.com>, "freebsd-hackers@freebsd.org" <freebsd-hackers@FreeBSD.org>
Subject:   Re: preemptive kernel
Message-ID:  <51A34EEA.9050609@FreeBSD.org>
In-Reply-To: <981733489AB3BD4DB24B48340F53E0A55B0D57D1@MTLDAG01.mtl.com>
References:  <981733489AB3BD4DB24B48340F53E0A55B0D5590@MTLDAG01.mtl.com> <20130526154752.GT3047@kib.kiev.ua> <981733489AB3BD4DB24B48340F53E0A55B0D56E0@MTLDAG01.mtl.com> <20130527063432.GY3047@kib.kiev.ua> <51A306A8.1010201@FreeBSD.org> <981733489AB3BD4DB24B48340F53E0A55B0D57D1@MTLDAG01.mtl.com>

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on 27/05/2013 10:21 Orit Moskovich said the following:
> What is actually the difference between deferring a filter routine's work using an ithread given to bus_setup_intr, or using the global taskqueue_swi (implemented using interrupt thread)?

I think you mean taskqueue_fast.
The difference is only in how much code you need to write.  I do not think there
is any significant difference in the resulting functionality.

> What do you mean that the functionality is locked under INTR_FILTER?

Please see the code.  You have to use option INTR_FILTER to get the behavior I
described earlier.

> -----Original Message-----
> From: Andriy Gapon [mailto:avg@FreeBSD.org] 
> Sent: Monday, May 27, 2013 10:11 AM
> To: Konstantin Belousov
> Cc: Orit Moskovich; freebsd-hackers@freebsd.org
> Subject: Re: preemptive kernel
> 
> on 27/05/2013 09:34 Konstantin Belousov said the following:
>> Having both filter and ithread for the same interrupt is apparently 
>> possible but weird.  I do not see anything which would prevent 
>> interrupt filter from being executed while the ithread is running.  
>> But again, this is very unusual setup.
> 
> I wouldn't call it weird, but, yes, it is rare.  It's a pretty normal configuration when the filter acts as a filter and the handler acts as a handler (in ithread).  In other words, it would be a replacement for a configuration where a filter is used and the filter offloads actual work to non-interrupt context via a e.g. taskqueue.
> But, hmm, this functionality is probably locked under INTR_FILTER option.
> 
> --
> Andriy Gapon
> 

-- 
Andriy Gapon



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