genirq: Add force argument to irq_startup()

In order to handle managed interrupts gracefully on irq_startup() so they
won't lose their assigned affinity, it's necessary to allow startups which
keep the interrupts in managed shutdown state, if none of the assigend CPUs
is online. This allows drivers to request interrupts w/o the CPUs being
online, which avoid online/offline churn in drivers.

Add a force argument which can override that decision and let only
request_irq() and enable_irq() allow the managed shutdown
handling. enable_irq() is required, because the interrupt might be
requested with IRQF_NOAUTOEN and enable_irq() invokes irq_startup() which
would then wreckage the assignment again. All other callers force startup
and potentially break the assigned affinity.

No functional change as this only adds the function argument.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Christoph Hellwig <hch@lst.de>
Link: http://lkml.kernel.org/r/20170619235447.112094565@linutronix.de

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 1163089aa245..b7599e952d3b 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -212,7 +212,7 @@ static int __irq_startup(struct irq_desc *desc)
 	return ret;
 }
 
-int irq_startup(struct irq_desc *desc, bool resend)
+int irq_startup(struct irq_desc *desc, bool resend, bool force)
 {
 	int ret = 0;
 
@@ -892,7 +892,7 @@ __irq_do_set_handler(struct irq_desc *desc, irq_flow_handler_t handle,
 		irq_settings_set_norequest(desc);
 		irq_settings_set_nothread(desc);
 		desc->action = &chained_action;
-		irq_startup(desc, true);
+		irq_startup(desc, IRQ_RESEND, IRQ_START_FORCE);
 	}
 }