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

kernel/irq/autoprobe.c

@@ -53,7 +53,7 @@ unsigned long probe_irq_on(void)
 			if (desc->irq_data.chip->irq_set_type)
 				desc->irq_data.chip->irq_set_type(&desc->irq_data,
 							 IRQ_TYPE_PROBE);
-			irq_startup(desc, false);
+			irq_startup(desc, IRQ_NORESEND, IRQ_START_FORCE);
 		}
 		raw_spin_unlock_irq(&desc->lock);
 	}
@@ -70,7 +70,7 @@ unsigned long probe_irq_on(void)
 		raw_spin_lock_irq(&desc->lock);
 		if (!desc->action && irq_settings_can_probe(desc)) {
 			desc->istate |= IRQS_AUTODETECT | IRQS_WAITING;
-			if (irq_startup(desc, false))
+			if (irq_startup(desc, IRQ_NORESEND, IRQ_START_FORCE))
 				desc->istate |= IRQS_PENDING;
 		}
 		raw_spin_unlock_irq(&desc->lock);

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);
 	}
 }
 

kernel/irq/internals.h

@@ -66,7 +66,14 @@ extern int __irq_set_trigger(struct irq_desc *desc, unsigned long flags);
 extern void __disable_irq(struct irq_desc *desc);
 extern void __enable_irq(struct irq_desc *desc);
 
-extern int irq_startup(struct irq_desc *desc, bool resend);
+#define IRQ_RESEND	true
+#define IRQ_NORESEND	false
+
+#define IRQ_START_FORCE	true
+#define IRQ_START_COND	false
+
+extern int irq_startup(struct irq_desc *desc, bool resend, bool force);
+
 extern void irq_shutdown(struct irq_desc *desc);
 extern void irq_enable(struct irq_desc *desc);
 extern void irq_disable(struct irq_desc *desc);

kernel/irq/manage.c

@@ -509,7 +509,7 @@ void __enable_irq(struct irq_desc *desc)
 		 * time. If it was already started up, then irq_startup()
 		 * will invoke irq_enable() under the hood.
 		 */
-		irq_startup(desc, true);
+		irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
 		break;
 	}
 	default:
@@ -1306,7 +1306,7 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, struct irqaction *new)
 		}
 
 		if (irq_settings_can_autoenable(desc)) {
-			irq_startup(desc, true);
+			irq_startup(desc, IRQ_RESEND, IRQ_START_COND);
 		} else {
 			/*
 			 * Shared interrupts do not go well with disabling