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Subject[PATCH v4] x86/irq: handle chained interrupts during IRQ migration
Date
Chained interrupt handlers dont have an irqaction and hence are not handled
during migrating interrupts when some cores go offline.

Handle this by introducing a irq_is_chained() check which is based on the the
CHAINED flag being set for such interrupts. fixup_irq() can then handle such
interrupts and not skip them over.

---
v1: use accessors instead of new variables to identify chained irqs
v2: use a mask of NOREQUEST, NOPROBE, and NOTHREAD accessor flags as per Paul M
v3: use a new accessor called IRQ_CHAINED instead of the mask in v2
v4: rebase against tip/irq/core branch

Signed-off-by: Sundar Iyer <sundar.iyer@intel.com>
Reviewed-by: Yang, Fei <fei.yang@intel.com>
Tested-by: Ng, Cheon-woei <cheon-woei.ng@intel.com>
---
arch/x86/kernel/irq.c | 10 ++++++----
include/linux/irq.h | 1 +
include/linux/irqdesc.h | 7 +++++++
kernel/irq/chip.c | 1 +
kernel/irq/settings.h | 8 ++++++++
5 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 3dafc60..352de40 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -255,10 +255,12 @@ void fixup_irqs(void)

data = irq_desc_get_irq_data(desc);
affinity = data->affinity;
- if (!irq_has_action(irq) || irqd_is_per_cpu(data) ||
- cpumask_subset(affinity, cpu_online_mask)) {
- raw_spin_unlock(&desc->lock);
- continue;
+ /* include IRQs who have no action, but are chained */
+ if ((!irq_has_action(irq) && !irq_is_chained(irq)) ||
+ irqd_is_per_cpu(data) ||
+ cpumask_subset(affinity, cpu_online_mask)) {
+ raw_spin_unlock(&desc->lock);
+ continue;
}

/*
diff --git a/include/linux/irq.h b/include/linux/irq.h
index 61f5cec..531fa31 100644
--- a/include/linux/irq.h
+++ b/include/linux/irq.h
@@ -97,6 +97,7 @@ enum {
IRQ_NESTED_THREAD = (1 << 15),
IRQ_NOTHREAD = (1 << 16),
IRQ_PER_CPU_DEVID = (1 << 17),
+ IRQ_CHAINED = (1 << 18),
};

#define IRQF_MODIFY_MASK \
diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
index f1e2527..785d608 100644
--- a/include/linux/irqdesc.h
+++ b/include/linux/irqdesc.h
@@ -123,6 +123,13 @@ static inline int irq_has_action(unsigned int irq)
return desc->action != NULL;
}

+/* Test to see if the IRQ is chained */
+static inline int irq_is_chained(unsigned int irq)
+{
+ struct irq_desc *desc = irq_to_desc(irq);
+ return desc->status_use_accessors & IRQ_CHAINED;
+}
+
/* caller has locked the irq_desc and both params are valid */
static inline void __irq_set_handler_locked(unsigned int irq,
irq_flow_handler_t handler)
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index eebd6d5..41e0208 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -657,6 +657,7 @@ __irq_set_handler(unsigned int irq, irq_flow_handler_t handle, int is_chained,
irq_settings_set_noprobe(desc);
irq_settings_set_norequest(desc);
irq_settings_set_nothread(desc);
+ irq_settings_set_chained(desc);
irq_startup(desc, true);
}
out:
diff --git a/kernel/irq/settings.h b/kernel/irq/settings.h
index 1162f10..bb8e167 100644
--- a/kernel/irq/settings.h
+++ b/kernel/irq/settings.h
@@ -15,6 +15,7 @@ enum {
_IRQ_NESTED_THREAD = IRQ_NESTED_THREAD,
_IRQ_PER_CPU_DEVID = IRQ_PER_CPU_DEVID,
_IRQF_MODIFY_MASK = IRQF_MODIFY_MASK,
+ _IRQ_CHAINED = IRQ_CHAINED,
};

#define IRQ_PER_CPU GOT_YOU_MORON
@@ -28,6 +29,7 @@ enum {
#define IRQ_PER_CPU_DEVID GOT_YOU_MORON
#undef IRQF_MODIFY_MASK
#define IRQF_MODIFY_MASK GOT_YOU_MORON
+#define IRQ_CHAINED GOT_YOU_MORON

static inline void
irq_settings_clr_and_set(struct irq_desc *desc, u32 clr, u32 set)
@@ -147,3 +149,9 @@ static inline bool irq_settings_is_nested_thread(struct irq_desc *desc)
{
return desc->status_use_accessors & _IRQ_NESTED_THREAD;
}
+
+static inline bool irq_settings_set_chained(struct irq_desc *desc)
+{
+ return desc->status_use_accessors |= _IRQ_CHAINED;
+}
+
--
1.7.0.4


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