s390/ism: clear dmbe_mask bit before SMC IRQ handling

SMC-D stress workload showed connection stalls. Since the firmware decides to skip raising an interrupt if the SBA DMBE mask bit is still set, this SBA DMBE mask bit should be cleared before the IRQ handling in the SMC code runs. Otherwise there are small windows possible with missing interrupts for incoming data.
SMC-D currently does not care about the old value of the SBA DMBE mask.

---
 drivers/s390/net/ism_drv.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

index f96ec68af2e5..dcbf5c857743 100644
@@ -415,9 +415,9 @@ static irqreturn_t ism_handle_irq(int irq, void *data)
 			break;
 
 		clear_bit_inv(bit, bv);
+		ism->sba->dmbe_mask[bit + ISM_DMB_BIT_OFFSET] = 0;
 		barrier();
 		smcd_handle_irq(ism->smcd, bit + ISM_DMB_BIT_OFFSET);
-		ism->sba->dmbe_mask[bit + ISM_DMB_BIT_OFFSET] = 0;
 	}
 
 	if (ism->sba->e) {

2.16.4