Subject: Re: [PATCH v3 22/25] irq_domain/x86: Convert x86 (embedded) to use common irq_domain

From: Sebastian Andrzej Siewior <[email-masked]>
Date: Sat, 28 Jan 2012 17:44:05 +0100

* Grant Likely | 2012-01-27 14:36:16 [-0700]:

>This patch removes the x86-specific definition of irq_domain and replaces
>it with the common implementation.

I pulled your devicetree/next tree. After this patch I get:

|Hierarchical RCU implementation.
|NR_IRQS:2304 nr_irqs:256 16
|------------[ cut here ]------------
|WARNING: at /home/bigeasy/work/shiva/git/linux-2.6-tip/kernel/irq/irqdomain.c:114 irq_domain_add_legacy+0x75/0x150()
|Modules linked in:
|Pid: 0, comm: swapper/0 Not tainted 3.3.0-rc1+ #65
|Call Trace:
| [<c15044e0>] ? printk+0x18/0x1a
| [<c102cdbd>] warn_slowpath_common+0x6d/0xa0
| [<c1095575>] ? irq_domain_add_legacy+0x75/0x150
| [<c1095575>] ? irq_domain_add_legacy+0x75/0x150
| [<c102ce0d>] warn_slowpath_null+0x1d/0x20
| [<c1095575>] irq_domain_add_legacy+0x75/0x150
| [<c1714824>] x86_add_irq_domains+0x96/0xd6
| [<c1708df2>] init_IRQ+0x8/0x33
| [<c170557f>] start_kernel+0x191/0x2e1
| [<c170517f>] ? loglevel+0x2b/0x2b
| [<c1705081>] i386_start_kernel+0x81/0x86
|---[ end trace 4eaa2a86a8e2da22 ]---
|------------[ cut here ]------------
|kernel BUG at /home/bigeasy/work/shiva/git/linux-2.6-tip/arch/x86/kernel/devicetree.c:367!

The warning is comming from this piece in irq_domain_add_legacy()
|for (i = 0; i < size; i++) {
|                 int irq = first_irq + i;
|                 struct irq_data *irq_data = irq_get_irq_data(irq);
| 
|                 if (WARN_ON(!irq_data || irq_data->domain)) {

irq_data is NULL here.

|                         mutex_unlock(&irq_domain_mutex);
|                         of_node_put(domain->of_node);
|                         kfree(domain);
|                         return NULL;
|                 }
|         }
| 

This is not always the case. arch_early_irq_init() in [0] sets up the
first 16 entries. The reminaing few (there is a toal of 24 irqs for
first ioapic and a second ioapic) are not initialized. This happens
later via ->xlate, ioapic_xlate() => io_apic_setup_irq_pin() =>
alloc_irq_and_cfg_at() calls irq_set_chip_data() on demand.

[0] arch/x86/kernel/apic/io_apic.c

Sebastian