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Message-ID: <20071209232208.GA1726@elf.ucw.cz> Date: Mon, 10 Dec 2007 00:22:08 +0100 From: Pavel Machek <pavel@....cz> To: Alan Cox <alan@...rguk.ukuu.org.uk> Cc: Andi Kleen <andi@...stfloor.org>, "David P. Reed" <dpreed@...d.com>, linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com> Subject: Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops On Sun 2007-12-09 22:29:28, Alan Cox wrote: > On Sun, 9 Dec 2007 22:25:13 +0100 > Pavel Machek <pavel@....cz> wrote: > > > On Sun 2007-12-09 17:59:08, Andi Kleen wrote: > > > > I mean, we expect 8usec delay -- historical ISA timing -- but when > > > > _PCI_ card with leds is inserted, it is likely to be faster than old > > > > ISA, right? > > > > > > Yes, i guess switching to udelay at least on newer systems would > > > be a good idea. I'm not quite sure about systems without TSC though. > > > > Something like this? (Warning, will not probably even compile on > > x86-64, I do not have 64-bit compiler near me). > > You need to stick in a bug trap to verify that the udelay is not called > before the cpu timer has been set up. Really? udelay() seems to use ... cpu_data(raw_smp_processor_id()).loops_per_jiffy .. ..so it seems that bug trap is already there... because raw_smp_processor_id() will probably just oops... We could solve this by pre-initializing loops_per_jiffy to some huge number, but I do not see convenient place where to do that. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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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