From: David Mosberger <davidm@napali.hpl.hp.com>
To: linux-ia64@vger.kernel.org
Subject: Re: Nested interrupts in IA64 linux?
Date: Sat, 14 Feb 2004 08:03:33 +0000 [thread overview]
Message-ID: <16429.54869.82093.174241@napali.hpl.hp.com> (raw)
In-Reply-To: <CC7A2BA2F1CA9E43B2B62C4783B42C7BBDC332@blr-ec-msg05.wipro.com>
>>>>> On Sat, 14 Feb 2004 12:10:27 +0530, ameya.mitragotri@wipro.com said:
Ameya> Does Linux support nested interrupts on IA64?
Yes.
Ameya> We are trying to do this because we want to dump (using LKCD)
Ameya> in a keyboard interrupt context. This dump performs write on
Ameya> the SCSI device(Fusion MPT), but we never seem to receive a
Ameya> SCSI interrupt indicating write completion.
Interrupts are divided into priority classes (16 vectors per class).
An interrupt at a vector that maps to a lower-or-equal class cannot
interrupt a pending interrupt. The exact irq mapping will depend on
your machine (and may depend on the kernel), but here is an example
for a zx2000:
$ cat /proc/interrupts
CPU0
28: 132 LSAPIC cpe_poll
29: 0 LSAPIC cmc_poll
31: 0 LSAPIC cmc_hndlr
48: 0 IO-SAPIC-level acpi
49: 15566 IO-SAPIC-edge serial
60: 30 IO-SAPIC-level sym53c8xx
61: 445042 IO-SAPIC-level sym53c8xx
62: 76142 IO-SAPIC-level ohci_hcd
63: 170072 IO-SAPIC-level ohci_hcd
64: 0 IO-SAPIC-level ehci_hcd
65: 19 IO-SAPIC-level ide1
66: 2985681 IO-SAPIC-level eth0
67: 0 IO-SAPIC-level FM801
232: 0 LSAPIC mca_rdzv
238: 0 LSAPIC perfmon
239: 121556726 LSAPIC timer
240: 0 LSAPIC mca_wkup
NMI: 0
ERR: 0
In this case, the SCSI controllers (sym53c8xx) are at vectors 60 and
61, which maps to priority class 3. The USB vectors (62-64) map to
either priority class 3 or 4, so it's not surprising that you don't
get any SCSI interrupts while handing a (USB) keyboard interrupt.
If you want to force SCSI interrupts to come through, you'd have to
lower the task-priority-register (TPR). You can see in
ia64_handle_irq() how this is done. Of course, do this at our own
risk!
--david
next prev parent reply other threads:[~2004-02-14 8:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-02-14 6:52 Nested interrupts in IA64 linux? ameya.mitragotri
2004-02-14 8:03 ` David Mosberger [this message]
2004-02-17 17:43 ` Luck, Tony
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