Subject: Re: lockdep and threaded IRQs (was: ...)
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: David Brownell <david-b@pacbell.net>
Cc: Ingo Molnar <mingo@elte.hu>, Andrew Morton <akpm@linux-foundation.org>,
       me@felipebalbi.com, linux-kernel@vger.kernel.org,
       linux-input@vger.kernel.org, felipe.balbi@nokia.com,
       dmitry.torokhov@gmail.com, sameo@openedhand.com, tglx@linutronix.de
In-Reply-To: <200903021837.08635.david-b@pacbell.net>
References: <1235762883-20870-1-git-send-email-me@felipebalbi.com>
	 <200903021633.08736.david-b@pacbell.net> <20090303004427.GA8638@elte.hu>
	 <200903021837.08635.david-b@pacbell.net>
Content-Type: text/plain
Date: Tue, 03 Mar 2009 10:27:26 +0100
Message-Id: <1236072446.18955.44.camel@twins>
Mime-Version: 1.0
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 925
Lines: 23

On Mon, 2009-03-02 at 18:37 -0800, David Brownell wrote:
> No.  But I did get a non-response that didn't include any
> explanation, and relied totally on unfounded assertions
> combined with the presumption that someday IRQF_DISABLED
> will be forced on in all drivers.

Enabling IRQs in hardirq context is BAD because:

 - IRQ handler nesting leads to stack overflow
 - It gives the false impression its OK for IRQ handlers to be slow,
   it is _NOT_, as you still generate horrible preemption latency.

Therefore IRQF_DISABLED _will_ be forced on everybody some day soon, and
I'll provide an IRQF_ENABLED for use by broken hardware only (and make a
TAINT flag for that too).


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/