[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <200911301253.29325.david-b@pacbell.net>
Date: Mon, 30 Nov 2009 12:53:28 -0800
From: David Brownell <david-b@...bell.net>
To: "Russell King - ARM Linux" <linux@....linux.org.uk>
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>,
Thomas Gleixner <tglx@...utronix.de>,
Rusty Russell <rusty@...tcorp.com.au>,
David Brownell <dbrownell@...rs.sourceforge.net>,
Eric Miao <eric.y.miao@...il.com>,
Andrea Gallo <andrea.gallo@...ricsson.com>,
Peter Zijlstra <peterz@...radead.org>,
John Stultz <johnstul@...ibm.com>,
Nicolas Pitre <nico@...vell.com>,
Jamie Lokier <jamie@...reable.org>,
LKML <linux-kernel@...r.kernel.org>,
Remy Bohmer <linux@...mer.net>,
Hugh Dickins <hugh.dickins@...cali.co.uk>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
"Uwe Kleine-König"
<u.kleine-koenig@...gutronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Ingo Molnar <mingo@...e.hu>,
linux-arm-kernel@...ts.infradead.org
Subject: Re: Get rid of IRQF_DISABLED - (was [PATCH] genirq: warn about IRQF_SHARED|IRQF_DISABLED)
On Monday 30 November 2009, Russell King - ARM Linux wrote:
> On Mon, Nov 30, 2009 at 02:47:02PM +0000, Alan Cox wrote:
> > SHARED|DISABLED ought to WARN_ON() and if that doesn't motivate people
> > then return -EINVAL.
>
> That is an impossibility. There is hardware out there (AT91) where
> the timer interrupt is shared with other peripherals, and you end
> up with a mixture of irqs-disabled and irqs-enabled handlers sharing
> the same interrupt.
For the record: AT91 isn't restricted to the system timers hooked
up on irq 0 ... there's also drivers/clocksource/tcb_clksrc.c (not
at the same hardware priority).
But to concur, this is indeed messy. Both the system timer and
the serial console generally share the same IRQ; both are very
timing-sensitive. I've seen console character dropouts after
tweaking timer IRQ handling. And I've never convinced myself
that Linux handles the hardware IRQ priority on those chips as
well as it could.
> My point is that if we outlaw irqs-disabled shared interrupts, it puts
> Atmel AT91 support into immediate difficulties.
ISTR that those TCB modules don't share IRQs with other peripherals.
Also, that Linux doesn't use them for much else. I've yet to see a
three-phase motor driver using the TCB's PWM capabilities, for example.
- Dave
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists