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Date: Tue, 10 Mar 2009 16:32:42 +0100 From: Ingo Molnar <mingo@...e.hu> To: Chris Friesen <cfriesen@...tel.com> Cc: linux-kernel@...r.kernel.org, Andi Kleen <andi@...stfloor.org>, "H. Peter Anvin" <hpa@...or.com>, Thomas Gleixner <tglx@...utronix.de>, Arjan van de Ven <arjan@...radead.org>, Yinghai Lu <yinghai@...nel.org> Subject: Re: reason for delay in arch/x86/kernel/traps.c::io_check_error()? * Chris Friesen <cfriesen@...tel.com> wrote: > Hi all, > > I was just wondering about the basis for the delay in > io_check_error(). The ICH7 manual doesn't have any mention of > a delay being required here--is it necessary for other > hardware, something not mentioned in the manual, or just an > accident? That code has seriously bitrotten along the years. All those port 61H accesses: arch/x86/kernel/traps.c: reason = get_nmi_reason(); arch/x86/kernel/traps.c: outb(reason, 0x61); arch/x86/kernel/traps.c: outb(reason, 0x61); arch/x86/kernel/traps.c: outb(reason, 0x61); ... are often wrong on modern chipsets - including the logic in io_check_error(). But we dont really have lowlevel chipset drivers on this level in Linux, so there's nothing suitable to replace it with and it never got fixed. Can you see this trigger on a box perhaps? Or are you worried about the potential unbound execution time of this function which can be up to 2 seconds in NMI context? Ingo -- 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/
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