linux-kernel - Re: [patch 00/47] Sparse irq rework

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Date:	Sat, 09 Oct 2010 00:08:37 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Grant Likely <grant.likely@...retlab.ca>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>, linux-arch@...r.kernel.org,
	Linus Torvalds <torvalds@...l.org>,
	Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mundt <lethal@...ux-sh.org>,
	David Woodhouse <dwmw2@...radead.org>,
	Jesse Barnes <jbarnes@...tuousgeek.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [patch 00/47] Sparse irq rework

On 10/08/2010 11:34 PM, Thomas Gleixner wrote:
> On Fri, 8 Oct 2010, Yinghai Lu wrote:
>> On 10/08/2010 09:26 PM, Yinghai Lu wrote:
>> [PATCH] x86: Don't setup ioapic irq for sci two times.
>>
>> With Thomas's sparseirq cleanup patchset, found one warning.
>>
>> [   37.369332] ------------[ cut here ]------------
>> [   37.383782] WARNING: at drivers/pci/intr_remapping.c:67 irq_2_iommu_alloc+0x52/0xdc()
>> [   37.384463] Hardware name: Sun Fire X4800
>> [   37.403803] irq_2_iommu!=NULL irq 9
>> [   37.404054] Modules linked in:
>> [   37.404311] Pid: 1, comm: swapper Not tainted 2.6.36-rc7-tip-yh-01944-ge8a4c5f-dirty #171
>> [   37.424042] Call Trace:
>> [   37.424205]  [<ffffffff810787a0>] warn_slowpath_common+0x85/0x9d
>> [   37.443822]  [<ffffffff8107885b>] warn_slowpath_fmt+0x46/0x48
>> [   37.444383]  [<ffffffff8141c5f6>] ? radix_tree_lookup+0xb/0xd
>> [   37.463788]  [<ffffffff8145f97c>] irq_2_iommu_alloc+0x52/0xdc
>> [   37.464200]  [<ffffffff81ccc593>] ? _raw_spin_lock_irqsave+0x6d/0x7b
>> [   37.483853]  [<ffffffff8145fb4d>] ? alloc_irte+0x97/0x168
>> [   37.484296]  [<ffffffff8145fbce>] alloc_irte+0x118/0x168
>> [   37.503774]  [<ffffffff8105062a>] setup_ioapic_irq+0x13f/0x331
>> [   37.504278]  [<ffffffff81051d70>] setup_IO_APIC_irq_extra+0xce/0xde
>> [   37.523868]  [<ffffffff8104c678>] acpi_gsi_to_irq+0x2a/0x31
>> ...
>>
>> It turns We could setup ioapic irq for sci two times if that is normal SCI.
>>
>> Actually setup_IO_APIC_irq_extra() is for big apic id or big irq sci.
>>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>>
>> ---
>>  arch/x86/kernel/apic/io_apic.c |    4 ++++
>>  1 file changed, 4 insertions(+)
>>
>> Index: linux-2.6/arch/x86/kernel/apic/io_apic.c
>> ===================================================================
>> --- linux-2.6.orig/arch/x86/kernel/apic/io_apic.c
>> +++ linux-2.6/arch/x86/kernel/apic/io_apic.c
>> @@ -1449,6 +1449,10 @@ void setup_IO_APIC_irq_extra(u32 gsi)
>>  
>>  	irq = pin_2_irq(idx, apic_id, pin);
>>  
>> +	/* only handle fall out from setup_IO_APIC_irqs() */
> 
> What's the fallout ? And why are we coming here in the first place
> when the irq is < 16 ?

setup_IO_APIC_irqs only handle apic_id == 0 or apic_id > 0 but irq < 16 via acpi override.

it seems IBM's system have apic_id == 1, and sci irq is using 30.

so at that time add that setup_IO_APIC_irq_extra() to workaround it.
but it seems we set that two time when irq < 16.

> 
>> +	if (!((apic_id > 0) && (irq > 16)))
>> +		return;
>> +
>>  	cfg = alloc_irq_and_cfg_at(irq, node);
>>  	if (!cfg)
>>  		return;
>>

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