Merge branch 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull irq fixes from Ingo Molnar:
 "Misc irq fixes:

   - two driver fixes
   - a Xen regression fix
   - a nested irq thread crash fix"

* 'irq-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  irqchip/gicv3-its: Fix mapping of LPIs to collections
  genirq: Prevent resend to interrupts marked IRQ_NESTED_THREAD
  genirq: Revert sparse irq locking around __cpu_up() and move it to x86 for now
  gpio/davinci: Fix race in installing chained irq handler

kernel/cpu.c

@@ -527,18 +527,9 @@ static int _cpu_up(unsigned int cpu, int tasks_frozen)
 		goto out_notify;
 	}
 
-	/*
-	 * Some architectures have to walk the irq descriptors to
-	 * setup the vector space for the cpu which comes online.
-	 * Prevent irq alloc/free across the bringup.
-	 */
-	irq_lock_sparse();
-
 	/* Arch-specific enabling code. */
 	ret = __cpu_up(cpu, idle);
 
-	irq_unlock_sparse();
-
 	if (ret != 0)
 		goto out_notify;
 	BUG_ON(!cpu_online(cpu));

kernel/irq/resend.c

@@ -75,13 +75,21 @@ void check_irq_resend(struct irq_desc *desc, unsigned int irq)
 		    !desc->irq_data.chip->irq_retrigger(&desc->irq_data)) {
 #ifdef CONFIG_HARDIRQS_SW_RESEND
 			/*
-			 * If the interrupt has a parent irq and runs
-			 * in the thread context of the parent irq,
-			 * retrigger the parent.
+			 * If the interrupt is running in the thread
+			 * context of the parent irq we need to be
+			 * careful, because we cannot trigger it
+			 * directly.
 			 */
-			if (desc->parent_irq &&
-			    irq_settings_is_nested_thread(desc))
+			if (irq_settings_is_nested_thread(desc)) {
+				/*
+				 * If the parent_irq is valid, we
+				 * retrigger the parent, otherwise we
+				 * do nothing.
+				 */
+				if (!desc->parent_irq)
+					return;
 				irq = desc->parent_irq;
+			}
 			/* Set it pending and activate the softirq: */
 			set_bit(irq, irqs_resend);
 			tasklet_schedule(&resend_tasklet);