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

1 files changed, 3 insertions, 3 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);
 	}