[PATCH 3/6] genirq: Delay deactivation in free_irq()

[Rishabh Bhatnagar <risbhat@amazon.com>]

From: Thomas Gleixner <tglx@linutronix.de>

commit 4001d8e8762f57d418b66e4e668601791900a1dd upstream.

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>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/20190628111440.098196390@linutronix.de
Signed-off-by: Rishabh Bhatnagar <risbhat@amazon.com>
---
 kernel/irq/autoprobe.c  |  6 +++---
 kernel/irq/chip.c       |  6 ++++++
 kernel/irq/cpuhotplug.c |  2 +-
 kernel/irq/internals.h  |  1 +
 kernel/irq/manage.c     | 10 ++++++++++
 5 files changed, 21 insertions(+), 4 deletions(-)

diff --git a/kernel/irq/autoprobe.c b/kernel/irq/autoprobe.c
index befa671fba64..39ff9ab34e82 100644
--- a/kernel/irq/autoprobe.c
+++ b/kernel/irq/autoprobe.c
@@ -92,7 +92,7 @@ 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;
@@ -129,7 +129,7 @@ unsigned int probe_irq_mask(unsigned long val)
 				mask |= 1 << i;
 
 			desc->istate &= ~IRQS_AUTODETECT;
-			irq_shutdown(desc);
+			irq_shutdown_and_deactivate(desc);
 		}
 		raw_spin_unlock_irq(&desc->lock);
 	}
@@ -171,7 +171,7 @@ 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);
 	}
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 317fc759de76..1936d86db883 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -293,6 +293,12 @@ 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
diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index 9eb09aef0313..a9f931217a1b 100644
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -115,7 +115,7 @@ static bool migrate_one_irq(struct irq_desc *desc)
 		 */
 		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;
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 5230c47fc43e..3de3821ab5fe 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -78,6 +78,7 @@ extern void __enable_irq(struct irq_desc *desc);
 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);
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index 722aeaae92b1..4e4fc7879307 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -14,6 +14,7 @@
 #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>
@@ -1604,6 +1605,7 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 	/* 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_hardirq() */
 		irq_shutdown(desc);
 	}
 
@@ -1673,6 +1675,14 @@ static struct irqaction *__free_irq(unsigned int irq, void *dev_id)
 		 * 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);
-- 
2.37.1