From: ebiederm@xmission.com (Eric W. Biederman)
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
linux-arch@vger.kernel.org, Linus Torvalds <torvalds@osdl.org>,
Andrew Morton <akpm@linux-foundation.org>,
x86@kernel.org, Peter Zijlstra <peterz@infradead.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mundt <lethal@linux-sh.org>,
Russell King <linux@arm.linux.org.uk>,
David Woodhouse <dwmw2@infradead.org>,
Jesse Barnes <jbarnes@virtuousgeek.org>,
Yinghai Lu <yinghai@kernel.org>,
Grant Likely <grant.likely@secretlab.ca>
Subject: Re: [patch 00/47] Sparse irq rework
Date: Sun, 03 Oct 2010 17:49:51 -0700 [thread overview]
Message-ID: <m162xibx3k.fsf@fess.ebiederm.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1010032034420.14550@localhost6.localdomain6> (Thomas Gleixner's message of "Sun, 3 Oct 2010 21:16:47 +0200 (CEST)")
Thomas Gleixner <tglx@linutronix.de> writes:
> On Sun, 3 Oct 2010, Eric W. Biederman wrote:
>> Thomas Gleixner <tglx@linutronix.de> writes:
>> > Rationale:
>> > ----------
>> >
>> > The current sparse_irq allocator has several short comings due to
>> > failures in the design or the lack of it:
>> >
>> > - Requires iteration over the number of active irqs to find a free slot
>> > Some architectures have grown their own workarounds for this.
>> >
>> > - Freeing of irq descriptors is not possible
>> >
>> > - Racy between create_irq_nr and destroy_irq plugged by horrible
>> > callbacks
>> >
>> > - Migration of active irq descriptors is not possible
>>
>> I believe you have distored the design when aiming for migration
>> of active irq descriptors (which you have not even implemented yet).
>>
>> How do you plan to remove the radix tree lookup from the irq
>> handling path?
>
> Not at all and it's not even even a requirement to remove the lookup
> for implementing live migration.
It sounds like it is a requirement to *keep* the lookup for supporting
live migration. *Keeping* the lookup I see as a serious problem. If we
do this right the only users of the radix tree will be drivers using the
functions in interrupt.h.
>> Those files provide the genirq irq chip implementation especially
>> drivers/pci/msi.c. Of course they will do what every other irq_chip
>> implementation does to get access to data. There is an unpleasant
>> difference between which generic irq data field htirq.c uses and msi.c
>> which may be worth cleaning up. But otherwise I don't see any
>> fundamental problems.
>
> The fundamental problem I hit, was the hack which handed down irq_desc
> to avoid the lookup. If it had been msi_desc in the first place, then
> I would not even need to touch the msi code to cleanup x86.
Just because you intend to rename the irq_desc irq_data...
It isn't a hack for an irq method to look at irq_desc. At least not
until your irq_data changes go through. This has nothing to do with
how x86 is structured and everything to do with your irq_data
``cleanup'' which appears to be mostly about code churn, for very little
apparent benefit.
In the current state of the kernel I find it very hard to swallow that
having a genirq client using irq_desc (which is the only way to
implement somethings) is a hack.
Eric
next prev parent reply other threads:[~2010-10-04 0:50 UTC|newest]
Thread overview: 118+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-30 23:14 [patch 00/47] Sparse irq rework Thomas Gleixner
2010-09-30 23:14 ` [patch 01/47] x86: Plug memory leak in sparse irq Thomas Gleixner
2010-09-30 23:14 ` [patch 02/47] x86: Hpet: Fix bogus error check in hpet_assign_irq() Thomas Gleixner
2010-09-30 23:14 ` [patch 03/47] genirq: Provide status modifier Thomas Gleixner
2010-09-30 23:14 ` [patch 04/47] arm: Use irq " Thomas Gleixner
2010-09-30 23:14 ` [patch 05/47] genirq-sanitize-irq-data-accessors.patch Thomas Gleixner
2010-09-30 23:15 ` [patch 06/47] genirq: Distangle kernel/irq/handle.c Thomas Gleixner
2010-09-30 23:15 ` [patch 07/47] genirq: Remove early_init_irq_lock_class() Thomas Gleixner
2010-09-30 23:15 ` [patch 08/47] genirq: Move core only inlines to kernel/irq Thomas Gleixner
2010-09-30 23:15 ` [patch 09/47] isdn: hisax: Replace the bogus access to irq stats Thomas Gleixner
2010-09-30 23:15 ` [patch 10/47] genirq: Remove export of kstat_irqs_cpu Thomas Gleixner
2010-09-30 23:15 ` [patch 11/47] genirq: Provide default irq init flags Thomas Gleixner
2010-09-30 23:15 ` [patch 12/47] arm: Use ARCH_IRQ_INIT_FLAGS Thomas Gleixner
2010-09-30 23:15 ` [patch 13/47] powerpc: " Thomas Gleixner
2010-09-30 23:15 ` [patch 14/47] genirq: Implement a sane sparse_irq allocator Thomas Gleixner
2010-10-01 5:28 ` Yinghai Lu
2010-10-01 20:36 ` Thomas Gleixner
2010-09-30 23:15 ` [patch 15/47] genirq: Prepare proc for real sparse irq support Thomas Gleixner
2010-09-30 23:15 ` [patch 16/47] genirq: Implement sane enumeration Thomas Gleixner
2010-10-03 10:55 ` Grant Likely
2010-09-30 23:15 ` [patch 17/47] genirq-update-kerneldoc.patch Thomas Gleixner
2010-09-30 23:16 ` [patch 18/47] genirq: Use sane sparse allocator Thomas Gleixner
2010-09-30 23:16 ` [patch 19/47] genirq: Query arch for number of early descriptors Thomas Gleixner
2010-09-30 23:16 ` [patch 20/47] x86: Remove useless reinitialization of irq descriptors Thomas Gleixner
2010-10-03 15:21 ` Eric W. Biederman
2010-10-03 18:26 ` Thomas Gleixner
2010-09-30 23:16 ` [patch 21/47] x86: Sanitize apb timer interrupt handling Thomas Gleixner
2010-09-30 23:16 ` [patch 22/47] x86: lguest: Convert to new irq chip functions Thomas Gleixner
2010-09-30 23:16 ` [patch 23/47] x86: Cleanup visws interrupt handling Thomas Gleixner
2010-09-30 23:16 ` [patch 24/47] x86: i8259: Convert to new irq_chip functions Thomas Gleixner
2010-09-30 23:16 ` [patch 25/47] x86: Cleanup io_apic Thomas Gleixner
2010-09-30 23:16 ` [patch 26/47] x86: io_apic: Convert startup to new irq_chip function Thomas Gleixner
2010-09-30 23:16 ` [patch 27/47] x86: ioapic: Convert mask " Thomas Gleixner
2010-09-30 23:16 ` [patch 28/47] x86: ioapic/hpet: Convert to new chip functions Thomas Gleixner
2010-09-30 23:16 ` [patch 29/47] pci: Convert msi to new irq_chip functions Thomas Gleixner
2010-10-11 17:09 ` Jesse Barnes
2010-09-30 23:16 ` [patch 30/47] dmar: Convert to new irq chip functions Thomas Gleixner
2010-09-30 23:17 ` [patch 31/47] ht: Convert to new irq_chip functions Thomas Gleixner
2010-09-30 23:17 ` [patch 32/47] x86: ioapic: Clean up the direct access to irq_desc Thomas Gleixner
2010-09-30 23:17 ` [patch 33/47] pci: Cleanup the irq_desc mess in msi Thomas Gleixner
2010-10-11 17:08 ` Jesse Barnes
2010-09-30 23:17 ` [patch 34/47] x86: ioapic: Convert irq affinity to new chip functions Thomas Gleixner
2010-09-30 23:17 ` [patch 35/47] x86: ioapic: Cleanup some more Thomas Gleixner
2010-09-30 23:17 ` [patch 36/47] x86: ioapic: Cleanup sparse irq code Thomas Gleixner
2010-09-30 23:17 ` [patch 37/47] x86: uv: Clean up the direct access to irq_desc Thomas Gleixner
2010-09-30 23:17 ` [patch 38/47] x86: Use sane enumeration Thomas Gleixner
2010-09-30 23:17 ` [patch 39/47] genirq: Remove arch_init_chip_data() Thomas Gleixner
2010-09-30 23:17 ` [patch 40/47] genirq: Sanitize dynamic irq handling Thomas Gleixner
2010-10-01 5:47 ` Yinghai Lu
2010-09-30 23:18 ` [patch 41/47] arm: davinci: Cleanup irq_desc access Thomas Gleixner
2010-09-30 23:18 ` [patch 42/47] genirq: Remove the now unused sparse irq leftovers Thomas Gleixner
2010-09-30 23:18 ` [patch 43/47] x86: xen: Sanitise sparse_irq handling Thomas Gleixner
2010-09-30 23:18 ` [patch 44/47] sh: Sanitize sparse irq Thomas Gleixner
2010-09-30 23:18 ` [patch 45/47] x86: lguest: Use new irq allocator Thomas Gleixner
2010-09-30 23:18 ` [patch 46/47] powerpc: " Thomas Gleixner
2010-10-01 0:42 ` Benjamin Herrenschmidt
2010-10-01 13:07 ` Thomas Gleixner
2010-10-01 20:46 ` Benjamin Herrenschmidt
2010-10-01 21:11 ` Grant Likely
2010-10-01 21:17 ` Benjamin Herrenschmidt
2010-10-03 16:53 ` Eric W. Biederman
2010-10-03 18:34 ` Thomas Gleixner
2010-10-03 20:04 ` Thomas Gleixner
2010-10-03 22:54 ` Benjamin Herrenschmidt
2010-10-04 0:15 ` Eric W. Biederman
2010-10-04 0:37 ` Benjamin Herrenschmidt
2010-10-04 16:46 ` Grant Likely
2010-09-30 23:18 ` [patch 47/47] genirq: Remove the old sparse irq allocator function Thomas Gleixner
2010-10-01 3:32 ` [patch 00/47] Sparse irq rework Linus Torvalds
2010-10-01 5:54 ` Yinghai Lu
2010-10-01 20:35 ` Thomas Gleixner
2010-10-03 11:23 ` Grant Likely
2010-10-03 11:29 ` Russell King - ARM Linux
2010-10-03 11:57 ` Grant Likely
2010-10-03 13:48 ` Thomas Gleixner
2010-10-05 10:22 ` Thomas Gleixner
2010-10-06 22:45 ` Yinghai Lu
2010-10-06 22:52 ` Thomas Gleixner
2010-10-06 23:37 ` Yinghai Lu
2010-10-07 0:16 ` Yinghai Lu
2010-10-07 4:01 ` Thomas Gleixner
2010-10-07 4:38 ` Yinghai Lu
2010-10-08 21:50 ` Thomas Gleixner
2010-10-08 21:54 ` Thomas Gleixner
2010-10-09 4:26 ` Yinghai Lu
2010-10-09 5:44 ` Yinghai Lu
2010-10-09 6:34 ` Thomas Gleixner
2010-10-09 7:08 ` Yinghai Lu
2010-10-09 7:08 ` Yinghai Lu
2010-10-09 12:08 ` Thomas Gleixner
2010-10-10 9:32 ` Thomas Gleixner
2010-10-10 13:30 ` Anca Emanuel
2010-10-11 2:20 ` Yinghai Lu
2010-10-11 2:20 ` Yinghai Lu
2010-10-11 3:50 ` Yinghai Lu
2010-10-11 3:50 ` Yinghai Lu
2010-10-11 8:16 ` Thomas Gleixner
2010-10-11 11:34 ` Benjamin Herrenschmidt
2010-10-11 16:19 ` Yinghai Lu
2010-10-11 16:19 ` Yinghai Lu
2010-10-12 20:23 ` [tip:irq/core] x86: Don't setup ioapic irq for sci twice tip-bot for Yinghai Lu
2010-10-09 6:10 ` [patch 00/47] Sparse irq rework Thomas Gleixner
2010-10-09 7:03 ` Yinghai Lu
2010-10-09 12:12 ` Thomas Gleixner
2010-10-10 2:32 ` Yinghai Lu
2010-10-10 2:32 ` Yinghai Lu
2010-10-10 5:11 ` Yinghai Lu
2010-10-10 5:11 ` Yinghai Lu
2010-10-10 8:20 ` Thomas Gleixner
2010-10-03 16:41 ` Eric W. Biederman
2010-10-03 16:41 ` Eric W. Biederman
2010-10-03 19:16 ` Thomas Gleixner
2010-10-03 22:57 ` Benjamin Herrenschmidt
2010-10-04 16:31 ` Grant Likely
2010-10-04 0:49 ` Eric W. Biederman [this message]
2010-10-04 8:05 ` Thomas Gleixner
2010-10-04 1:13 ` Eric W. Biederman
2010-10-04 6:36 ` Ingo Molnar
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