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From: David Miller <davem@davemloft.net>
To: torvalds@linux-foundation.org
Cc: matthew@wil.cx, mingo@elte.hu, linux-kernel@vger.kernel.org
Subject: Re: IRQF_DISABLED problem
Date: Thu, 26 Jul 2007 16:14:41 -0700 (PDT)	[thread overview]
Message-ID: <20070726.161441.38711978.davem@davemloft.net> (raw)
In-Reply-To: <alpine.LFD.0.999.0707261557150.3442@woody.linux-foundation.org>

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Thu, 26 Jul 2007 16:04:42 -0700 (PDT)

> Quite frankly, my preference would be (a) followed by (e) or (f), and 
> (b)-(d) are in my opinion the worst of the lot with no upsides at all (and 
> (b) in particular is pretty much _guaranteed_ to break existing setups).

I look at some cases, such as EHEA on powerpc which is a pretty
modern driver written by not clueless folks, and wonder if they
do it because they know the IRQ is non-shared, they know their
interrupt handler is insanely simple and short, and just want to
avoid the overhead of that sti()/cli() in the caller.

All the EHEA interrupt handler does is unconditionally set a state bit
and schedule a softirq, then return.

The powerpc folks do delayed IRQ enable/disable using software state,
but perhaps these drivers were written before that.

  reply	other threads:[~2007-07-27  0:13 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-07-26 20:13 Matthew Wilcox
2007-07-26 20:41 ` Linus Torvalds
2007-07-26 22:23 ` David Miller
2007-07-26 23:04   ` Linus Torvalds
2007-07-26 23:14     ` David Miller [this message]
2007-07-26 23:17     ` Linus Torvalds
2007-07-27 20:11       ` Arjan van de Ven
2007-07-27 20:50         ` David Miller
     [not found] <fa.mb8woD3e5JnT1x6AgEMOmnlVvg0@ifi.uio.no>
     [not found] ` <fa.axY2ukp7kqKVMAidyu4NVN81MbI@ifi.uio.no>
     [not found]   ` <fa.tS+LCGnYgeCNRIaF90yH21XBCqI@ifi.uio.no>
     [not found]     ` <fa./08N/HtpJQ6zg8Xc1K5pP6/aKMM@ifi.uio.no>
2007-07-29 15:41       ` Robert Hancock
2007-08-02 15:40         ` Mark Lord

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