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Date: Wed, 28 Feb 2007 00:51:18 -0800 (PST) From: Zwane Mwaikambo <zwane@...radead.org> To: "Eric W. Biederman" <ebiederm@...ssion.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, Chuck Ebbert <cebbert@...hat.com>, Andi Kleen <ak@...e.de>, Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org, stable@...nel.org, Justin Forbes <jmforbes@...uxtx.org>, Theodore Ts'o <tytso@....edu>, Randy Dunlap <rdunlap@...otime.net>, Dave Jones <davej@...hat.com>, Chuck Wolber <chuckw@...ntumlinux.com>, Chris Wedgwood <reviews@...cw.f00f.org>, Michael Krufky <mkrufky@...uxtv.org>, alan@...rguk.ukuu.org.uk Subject: Re: [patch 00/21] 2.6.19-stable review On Tue, 27 Feb 2007, Eric W. Biederman wrote: > > http://www.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.20/2.6.20-mm2/broken-out/x86_64-mm-handle-irqs-pending-in-irr-during-irq-migration.patch > >> > >> That's mainly an Andi decision. Let's cc him. > > > > Would be good to have Eric also ack them as safe and obvious. > > > > Btw, that latter one has corrupted sign-offs from Andi (it's in the middle > > of the text, very confusing). > > There are two questions. > 1) What can we do to make the situation better. > 2) Is the hole completely plugged. > > When I wrote the patch I had the local apic priorities backwards in my > head. So apic_in_service_vector can return the wrong value if two > irqs are in service. Now I don't think we allows ourselves to enable > interrupts in an interrupt service routing until after we have acked > the local apic so this should be harmless. The fix is also trivial > of just having apic_in_service_vector return: "~get_irq_regs()->orig_rax". > > Except for that one possible problem everything I can think of are > just theoretical cracks at this point, and they don't make the > situation any worse. > > Given that this patch has appears to have undergone a noticeable > amount of testing, by people other than myself, and clears up the > symptoms. I have no problem Hi Eric, Thanks for getting this cruft cleaned up. I have a few comments regarding; handle-irqs-pending-in-irr-during-irq-migration.patch 1) It relies on checking the IRR, this could race with the corresponding vector bit being set by hardware. 2) apic_handle_pending_vector is oddly named since it doesn't actually handle a pending vector but drops it if it has been freed. 3) It looks complex So how about the following scheme. Add a check in do_IRQ whether the irq's domain contains the current cpu, if not we free the vector upon handler completion. Cheers, Zwane - 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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