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From: ebiederm@xmission.com (Eric W. Biederman)
To: "Natalie Protasevich" <protasnb@gmail.com>
Cc: "Zwane Mwaikambo" <zwane@infradead.org>,
	"Ashok Raj" <ashok.raj@intel.com>, "Ingo Molnar" <mingo@elte.hu>,
	"Andrew Morton" <akpm@osdl.org>,
	linux-kernel@vger.kernel.org, "Lu, Yinghai" <yinghai.lu@amd.com>,
	"Andi Kleen" <ak@suse.de>, "Coywolf Qi Hunt" <coywolf@lovecn.org>
Subject: Re: What are the real ioapic rte programming constraints?
Date: Sun, 11 Feb 2007 14:36:47 -0700	[thread overview]
Message-ID: <m1ejowz89c.fsf@ebiederm.dsl.xmission.com> (raw)
In-Reply-To: <32209efe0702111212j77f5011xe2430cb13c13686@mail.gmail.com> (Natalie Protasevich's message of "Sun, 11 Feb 2007 12:12:19 -0800")

"Natalie Protasevich" <protasnb@gmail.com> writes:

> On 2/11/07, Eric W. Biederman <ebiederm@xmission.com> wrote:
>
>     The code currently in the kernel does:
>
>     pending
>     mask
>     read io_apic
>     ack
>     reprogram vector and destination
>     unmask
>
>     So I guess it does retain the bug fix.
>
>     What I am looking at doing is:
>
>     mask
>     read io_apic
>     -- Past this point no more irqs are expected from the io_apic
>     -- Now I work to drain any inflight/pending instances of the irq
>     send ipi to all irq destinations cpus and wait for it to return
>     read lapic
>     disable local irqs
>     take irq lock
>     -- Now no more irqs are expected to arrive
>     reprogram vector and destination
>     enable local irqs
>     unmask
>
>     What I need to ensure is that I have a point where I will not receive any
>     new messages from an ioapic about a particular irq anymore.  Even if
>     everything is working perfectly setting the disable bit is not enough
>     because there could be an irq message in flight. So I need to give any
>     in flight irqs a chance to complete.
>
>
> It is probably safer to have "interlapping" time in having second rte
> programmed, then both willl have the same vector and receive the eoi. And if
> you have interrupts disabled for a little while before you dismantle the old
> entry it should insure that all the in-flight ones got services and acked...
> --Natalie

I am assuming you mean interrupts disabled at the ioapic.  If that
is true mostly I agree with your assertion.

If you look above the mask is where I disable that interrupt source on
the ioapic.  I then send an ipi to all of the other possible cpus and
read the local apic to ensure that the window is over in which I need
to handle interrupts at the old destination. 

If I don't know when the window ends I can never dismantle the data
structures for receiving the irq at the old destination.  Ouch!

If I know how long I have to wait until I can clean up the data
structure at the old destination I don't have to worry about
overlapping interrupts.

Therefore it doesn't by me anything but complexity to setup the data
structures on the new cpu before the window for receiving the irqs
has completed.

Make sense?

Eric




  parent reply	other threads:[~2007-02-11 21:38 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <200701221116.13154.luigi.genoni@pirelli.com>
2007-01-22 17:14 ` System crash after "No irq handler for vector" linux 2.6.19 Eric W. Biederman
     [not found]   ` <200701231051.32945.luigi.genoni@pirelli.com>
2007-01-23 12:18     ` Eric W. Biederman
     [not found]       ` <Pine.LNX.4.64.0701232052330.32111@baldios.it.pirelli.com>
2007-01-31  8:39         ` Eric W. Biederman
     [not found]           ` <200701311549.22512.luigi.genoni@pirelli.com>
2007-02-01  5:56             ` [PATCH] x86_64: Survive having no irq mapping for a vector Eric W. Biederman
2007-02-01  5:59             ` System crash after "No irq handler for vector" linux 2.6.19 Eric W. Biederman
2007-02-01  7:20             ` Eric W. Biederman
     [not found]               ` <200702021848.55921.luigi.genoni@pirelli.com>
2007-02-02 18:02                 ` Eric W. Biederman
     [not found]                   ` <200702021905.39922.luigi.genoni@pirelli.com>
2007-02-02 18:32                     ` Eric W. Biederman
2007-02-03  0:31                     ` [PATCH 1/2] x86_64 irq: Simplfy __assign_irq_vector Eric W. Biederman
2007-02-03  0:35                       ` [PATCH 2/2] x86_64 irq: Handle irqs pending in IRR during irq migration Eric W. Biederman
2007-02-03  1:05                         ` Andrew Morton
2007-02-03  1:39                           ` Eric W. Biederman
2007-02-03  2:01                             ` Andrew Morton
2007-02-03  7:32                           ` Arjan van de Ven
2007-02-03  7:55                             ` Eric W. Biederman
2007-02-03 14:31                               ` l.genoni
2007-02-03 10:01                         ` Andi Kleen
2007-02-03 10:22                           ` Eric W. Biederman
2007-02-03 10:26                             ` Andi Kleen
2007-02-06  7:36                         ` Ingo Molnar
2007-02-06  8:57                           ` Eric W. Biederman
     [not found]                           ` <200702061012.25910.luigi.genoni@pirelli.com>
2007-02-06 22:05                             ` Eric W. Biederman
2007-02-06 22:16                           ` Eric W. Biederman
2007-02-06 22:25                             ` Ingo Molnar
2007-02-07  2:33                               ` Eric W. Biederman
2007-02-08 11:48                               ` Eric W. Biederman
2007-02-08 20:19                                 ` Eric W. Biederman
2007-02-09  6:40                                   ` Eric W. Biederman
2007-02-10 23:52                                     ` What are the real ioapic rte programming constraints? Eric W. Biederman
2007-02-11  5:57                                       ` Zwane Mwaikambo
2007-02-11 10:20                                         ` Eric W. Biederman
2007-02-11 16:16                                           ` Zwane Mwaikambo
2007-02-11 22:01                                             ` Eric W. Biederman
2007-02-12  1:05                                               ` Zwane Mwaikambo
2007-02-12  4:51                                                 ` Eric W. Biederman
2007-02-23 10:51                                                   ` Conclusions from my investigation about ioapic programming Eric W. Biederman
2007-02-23 11:10                                                     ` [PATCH 0/14] x86_64 irq related fixes and cleanups Eric W. Biederman
2007-02-23 11:11                                                       ` [PATCH 01/14] x86_64 irq: Simplfy __assign_irq_vector Eric W. Biederman
2007-02-23 11:13                                                         ` [PATCH 02/14] irq: Remove set_native_irq_info Eric W. Biederman
2007-02-23 11:15                                                           ` [PATCH 03/14] x86_64 irq: Kill declaration of removed array, interrupt Eric W. Biederman
2007-02-23 11:16                                                             ` [PATCH 04/14] x86_64 irq: Remove the unused vector parameter from ioapic_register_intr Eric W. Biederman
2007-02-23 11:19                                                               ` [PATCH 05/14] x86_64 irq: Refactor setup_IO_APIC_irq Eric W. Biederman
2007-02-23 11:20                                                                 ` [PATCH 06/14] x86_64 irq: Simplfiy the set_affinity logic Eric W. Biederman
2007-02-23 11:23                                                                   ` [PATCH 07/14] x86_64 irq: In __DO_ACTION perform the FINAL action for every entry Eric W. Biederman
2007-02-23 11:26                                                                     ` [PATCH 08/14] x86_64 irq: Use NR_IRQS not NR_IRQ_VECTORS Eric W. Biederman
2007-02-23 11:32                                                                       ` [PATCH 09/14] x86_64 irq: Begin consolidating per_irq data in structures Eric W. Biederman
2007-02-23 11:35                                                                         ` [PATCH 10/14] x86_64 irq: Simplify assign_irq_vector's arguments Eric W. Biederman
2007-02-23 11:36                                                                           ` [PATCH 11/14] x86_64 irq: Remove unnecessary irq 0 setup Eric W. Biederman
2007-02-23 11:38                                                                             ` [PATCH 12/14] x86_64 irq: Add constants for the reserved IRQ vectors Eric W. Biederman
2007-02-23 11:40                                                                               ` [PATCH 13/14] x86_64 irq: Safely cleanup an irq after moving it Eric W. Biederman
2007-02-25 11:53                                                                                 ` Mika Penttilä
2007-02-25 12:09                                                                                   ` Eric W. Biederman
2007-02-23 11:46                                                                               ` [PATCH 14/14] genirq: Mask irqs when migrating them Eric W. Biederman
2007-02-23 12:01                                                                                 ` [PATCH] x86_64 irq: Document what works and why on ioapics Eric W. Biederman
2007-02-24  2:06                                                                                 ` [PATCH 14/14] genirq: Mask irqs when migrating them Siddha, Suresh B
2007-02-27 20:26                                                                                   ` Andrew Morton
2007-02-27 20:41                                                                                     ` Eric W. Biederman
2007-02-25 10:43                                                                               ` [PATCH 12/14] x86_64 irq: Add constants for the reserved IRQ vectors Pavel Machek
2007-02-25 11:15                                                                                 ` Eric W. Biederman
2007-02-25 19:48                                                                                   ` Pavel Machek
2007-02-25 21:01                                                                                     ` Eric W. Biederman
2007-02-25 21:13                                                                                       ` Pavel Machek
2007-02-23 16:48                                                     ` Conclusions from my investigation about ioapic programming Jeff V. Merkey
2007-02-23 18:10                                                       ` Eric W. Biederman
2007-02-23 17:48                                                         ` Jeff V. Merkey
2007-02-24  4:05                                                           ` Eric W. Biederman
2007-02-24  5:44                                                             ` Jeffrey V. Merkey
2007-02-23 17:48                                                         ` Jeff V. Merkey
     [not found]                                           ` <32209efe0702111212j77f5011xe2430cb13c13686@mail.gmail.com>
2007-02-11 21:36                                             ` Eric W. Biederman [this message]
2007-02-03  9:50                       ` [PATCH 1/2] x86_64 irq: Simplfy __assign_irq_vector Andi Kleen
2007-02-03  0:40                     ` System crash after "No irq handler for vector" linux 2.6.19 Eric W. Biederman

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