ArmPkg/ArmGicDxe: Fix double GIC EIOR write per interrupt

This commit fixes a bug in the GIC v2 and v3 drivers where the GICC_EOIR
(End Of Interrupt Register) is written twice for a single interrupt.
GicV(2|3)IrqInterruptHandler() calls the Interrupt Handler and then
GicV(2|3)EndOfInterrupt() on exit:

 InterruptHandler = gRegisteredInterruptHandlers[GicInterrupt];
 if (InterruptHandler != NULL) {
   // Call the registered interrupt handler.
   InterruptHandler (GicInterrupt, SystemContext);
 } else {
   DEBUG ((EFI_D_ERROR, "Spurious GIC interrupt: 0x%x\n", GicInterrupt));
 }

 GicV2EndOfInterrupt (&gHardwareInterruptV2Protocol, GicInterrupt);

although gInterrupt->EndOfInterrupt() can be expected to have already
been called by InterruptHandler() [which is the case for the primary
in-tree handler in TimerDxe]

The fix moves the EndOfInterrupt() call inside the else case for
unregistered/spurious interrupts. This removes a potential race
condition that might have lost interrupts.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Alexei Fedorov <alexei.fedorov@arm.com>
Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/ArmPkg/Drivers/ArmGic/GicV2/ArmGicV2Dxe.c b/ArmPkg/Drivers/ArmGic/GicV2/ArmGicV2Dxe.c
index 036eb5cd6b..34d4be3867 100644
--- a/ArmPkg/Drivers/ArmGic/GicV2/ArmGicV2Dxe.c
+++ b/ArmPkg/Drivers/ArmGic/GicV2/ArmGicV2Dxe.c
@@ -2,7 +2,7 @@
 

 Copyright (c) 2009, Hewlett-Packard Company. All rights reserved.<BR>

 Portions copyright (c) 2010, Apple Inc. All rights reserved.<BR>

-Portions copyright (c) 2011-2015, ARM Ltd. All rights reserved.<BR>

+Portions copyright (c) 2011-2016, ARM Ltd. All rights reserved.<BR>

 

 This program and the accompanying materials

 are licensed and made available under the terms and conditions of the BSD License

@@ -178,9 +178,8 @@ GicV2IrqInterruptHandler (
     InterruptHandler (GicInterrupt, SystemContext);

   } else {

     DEBUG ((EFI_D_ERROR, "Spurious GIC interrupt: 0x%x\n", GicInterrupt));

+    GicV2EndOfInterrupt (&gHardwareInterruptV2Protocol, GicInterrupt);

   }

-

-  GicV2EndOfInterrupt (&gHardwareInterruptV2Protocol, GicInterrupt);

 }

 

 //