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Subject[patch 1/5] genirq: Delay deactivation in free_irq()
When interrupts are shutdown, they are immediately deactivated in the
irqdomain hierarchy. While this looks obviously correct there is a subtle
issue:

There might be an interrupt in flight when free_irq() is invoking the
shutdown. This is properly handled at the irq descriptor / primary handler
level, but the deactivation might completely disable resources which are
required to acknowledge the interrupt.

Split the shutdown code and deactivate the interrupt after synchronization
in free_irq(). Fixup all other usage sites where this is not an issue to
invoke the combined shutdown_and_deactivate() function instead.

This still might be an issue if the interrupt in flight servicing is
delayed on a remote CPU beyond the invocation of synchronize_irq(), but
that cannot be handled at that level and needs to be handled in the
synchronize_irq() context.

Fixes: f8264e34965a ("irqdomain: Introduce new interfaces to support hierarchy irqdomains")
Reported-by: Robert Hodaszi <Robert.Hodaszi@digi.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
kernel/irq/autoprobe.c | 6 +++---
kernel/irq/chip.c | 6 ++++++
kernel/irq/cpuhotplug.c | 2 +-
kernel/irq/internals.h | 1 +
kernel/irq/manage.c | 12 +++++++++++-
5 files changed, 22 insertions(+), 5 deletions(-)

--- a/kernel/irq/autoprobe.c
+++ b/kernel/irq/autoprobe.c
@@ -90,7 +90,7 @@ unsigned long probe_irq_on(void)
/* It triggered already - consider it spurious. */
if (!(desc->istate & IRQS_WAITING)) {
desc->istate &= ~IRQS_AUTODETECT;
- irq_shutdown(desc);
+ irq_shutdown_and_deactivate(desc);
} else
if (i < 32)
mask |= 1 << i;
@@ -127,7 +127,7 @@ unsigned int probe_irq_mask(unsigned lon
mask |= 1 << i;

desc->istate &= ~IRQS_AUTODETECT;
- irq_shutdown(desc);
+ irq_shutdown_and_deactivate(desc);
}
raw_spin_unlock_irq(&desc->lock);
}
@@ -169,7 +169,7 @@ int probe_irq_off(unsigned long val)
nr_of_irqs++;
}
desc->istate &= ~IRQS_AUTODETECT;
- irq_shutdown(desc);
+ irq_shutdown_and_deactivate(desc);
}
raw_spin_unlock_irq(&desc->lock);
}
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -314,6 +314,12 @@ void irq_shutdown(struct irq_desc *desc)
}
irq_state_clr_started(desc);
}
+}
+
+
+void irq_shutdown_and_deactivate(struct irq_desc *desc)
+{
+ irq_shutdown(desc);
/*
* This must be called even if the interrupt was never started up,
* because the activation can happen before the interrupt is
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -116,7 +116,7 @@ static bool migrate_one_irq(struct irq_d
*/
if (irqd_affinity_is_managed(d)) {
irqd_set_managed_shutdown(d);
- irq_shutdown(desc);
+ irq_shutdown_and_deactivate(desc);
return false;
}
affinity = cpu_online_mask;
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -82,6 +82,7 @@ extern int irq_activate_and_startup(stru
extern int irq_startup(struct irq_desc *desc, bool resend, bool force);

extern void irq_shutdown(struct irq_desc *desc);
+extern void irq_shutdown_and_deactivate(struct irq_desc *desc);
extern void irq_enable(struct irq_desc *desc);
extern void irq_disable(struct irq_desc *desc);
extern void irq_percpu_enable(struct irq_desc *desc, unsigned int cpu);
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -13,6 +13,7 @@
#include <linux/module.h>
#include <linux/random.h>
#include <linux/interrupt.h>
+#include <linux/irqdomain.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/sched/rt.h>
@@ -1699,6 +1700,7 @@ static struct irqaction *__free_irq(stru
/* If this was the last handler, shut down the IRQ line: */
if (!desc->action) {
irq_settings_clr_disable_unlazy(desc);
+ /* Only shutdown. Deactivate after synchronize_irq() */
irq_shutdown(desc);
}

@@ -1768,6 +1770,14 @@ static struct irqaction *__free_irq(stru
* require it to deallocate resources over the slow bus.
*/
chip_bus_lock(desc);
+ /*
+ * There is no interrupt on the fly anymore. Deactivate it
+ * completely.
+ */
+ raw_spin_lock_irqsave(&desc->lock, flags);
+ irq_domain_deactivate_irq(&desc->irq_data);
+ raw_spin_unlock_irqrestore(&desc->lock, flags);
+
irq_release_resources(desc);
chip_bus_sync_unlock(desc);
irq_remove_timings(desc);
@@ -1855,7 +1865,7 @@ static const void *__cleanup_nmi(unsigne
}

irq_settings_clr_disable_unlazy(desc);
- irq_shutdown(desc);
+ irq_shutdown_and_deactivate(desc);

irq_release_resources(desc);


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