Revert "s390/pci: remove bit_lock usage in interrupt handler"

This reverts commit 9594ca6b.

With the handle_simple_irq irq_flow_handler it must be ensured to
not call generic_handle_irq with the same IRQ number on 2 CPUs at
the same time (interrupts are floating on s390).
Contrary to my initial investigation the irq_desc's lock usage in
handle_simple_irq does not ensure this. Thus re-introduce the bit-
lock usage in s390's pci handler.
Reported-by: NUrsula Braun <ubraun@linux.ibm.com>
Reported-by: NAlexander Schmidt <alexs@linux.ibm.com>
Signed-off-by: NSebastian Ott <sebott@linux.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/pci/pci.c

@@ -382,7 +382,9 @@ static void zpci_irq_handler(struct airq_struct *airq)
 			if (ai == -1UL)
 				break;
 			inc_irq_stat(IRQIO_MSI);
+			airq_iv_lock(aibv, ai);
 			generic_handle_irq(airq_iv_get_data(aibv, ai));
+			airq_iv_unlock(aibv, ai);
 		}
 	}
 }
@@ -408,7 +410,7 @@ int arch_setup_msi_irqs(struct pci_dev *pdev, int nvec, int type)
 	zdev->aisb = aisb;
 
 	/* Create adapter interrupt vector */
-	zdev->aibv = airq_iv_create(msi_vecs, AIRQ_IV_DATA);
+	zdev->aibv = airq_iv_create(msi_vecs, AIRQ_IV_DATA | AIRQ_IV_BITLOCK);
 	if (!zdev->aibv)
 		return -ENOMEM;