genirq: Provide interrupt injection mechanism

Error injection mechanisms need a half ways safe way to inject interrupts as
invoking generic_handle_irq() or the actual device interrupt handler
directly from e.g. a debugfs write is not guaranteed to be safe.

On x86 generic_handle_irq() is unsafe due to the hardware trainwreck which
is the base of x86 interrupt delivery and affinity management.

Move the irq debugfs injection code into a separate function which can be
used by error injection code as well.

The implementation prevents at least that state is corrupted, but it cannot
close a very tiny race window on x86 which might result in a stale and not
serviced device interrupt under very unlikely circumstances.

This is explicitly for debugging and testing and not for production use or
abuse in random driver code.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Link: https://lkml.kernel.org/r/20200306130623.990928309@linutronix.de

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index b3fa2d87d2f3..41e7e37a0928 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -278,7 +278,7 @@ int irq_startup(struct irq_desc *desc, bool resend, bool force)
 		}
 	}
 	if (resend)
-		check_irq_resend(desc);
+		check_irq_resend(desc, false);
 
 	return ret;
 }