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>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Link: https://lkml.kernel.org/r/20190628111440.098196390@linutronix.de

5 files changed, 22 insertions, 5 deletions

diff --git a/kernel/irq/autoprobe.c b/kernel/irq/autoprobe.c
index 16cbf6beb276..ae60cae24e9a 100644
--- 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 long val)
                                 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);
         }
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 51128bea3846..04fe4f989bd8 100644
--- 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
diff --git a/kernel/irq/cpuhotplug.c b/kernel/irq/cpuhotplug.c
index 5b1072e394b2..6c7ca2e983a5 100644
--- a/kernel/irq/cpuhotplug.c
+++ b/kernel/irq/cpuhotplug.c
@@ -116,7 +116,7 @@ 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 70c3053bc1f6..9c957f8b1198 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -82,6 +82,7 @@ extern int irq_activate_and_startup(struct irq_desc *desc, bool resend);
 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 53a081392115..dc8b35f2d545 100644
--- 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(struct irq_desc *desc, 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);
         }
 
@@ -1768,6 +1770,14 @@ static struct irqaction *__free_irq(struct irq_desc *desc, 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);
@@ -1855,7 +1865,7 @@ static const void *__cleanup_nmi(unsigned int irq, struct irq_desc *desc)
         }
 
         irq_settings_clr_disable_unlazy(desc);
-        irq_shutdown(desc);
+        irq_shutdown_and_deactivate(desc);
 
         irq_release_resources(desc);