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Subject[PATCH v4 5/6] irqdomain: add IRQ_DOMAIN_FLAG_NO_CREATE flag
Date
When an irqchip driver uses irq_domain_push_irq(), all irqs should be
statically created by the irqchip.

If a device tries to allocate an irq on-the-fly, irq_domain_alloc_irqs()
is called. It allocates struct irq_data and invokes .alloc() hook
passing fwspec as its argument. This is probably not what the irqchip
expects (unless .alloc can call it recursively).

This issue could happen when a device tries to get irq after
irq_domain_create_hierarchy(), but before irq_domain_push_irq().

To avoid the race, add IRQ_DOMAIN_FLAG_NO_CREATE flag. This flag
prevents devices from creating irqs. Devices are only allowed to get
already existing irqs.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

Changes in v4:
- Newly added


include/linux/irqdomain.h | 3 +++
kernel/irq/irqdomain.c | 3 +++
2 files changed, 6 insertions(+)

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 7609807..525de32 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -195,6 +195,9 @@ enum {
/* Irq domain name was allocated in __irq_domain_add() */
IRQ_DOMAIN_NAME_ALLOCATED = (1 << 6),

+ /* Do not allow irq consumers to create irq */
+ IRQ_DOMAIN_FLAG_NO_CREATE = (1 << 7),
+
/*
* Flags starting from IRQ_DOMAIN_FLAG_NONCORE are reserved
* for implementation specific purposes and ignored by the
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index b317a64..ecf107ab 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -806,6 +806,9 @@ unsigned int irq_create_fwspec_mapping(struct irq_fwspec *fwspec)
return 0;
}

+ if (domain->flags & IRQ_DOMAIN_FLAG_NO_CREATE)
+ return -EPROBE_DEFER;
+
if (irq_domain_is_hierarchy(domain)) {
virq = irq_domain_alloc_irqs(domain, 1, NUMA_NO_NODE, fwspec);
if (virq <= 0)
--
2.7.4
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