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.

Acked-by: Sebastian Ott <sebott@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/s390/net/ism_drv.c b/drivers/s390/net/ism_drv.c
index f96ec68af2e58aabfa0bdb71dde1f05ff8ad4151..dcbf5c857743782871d9be3dfe51f9fee3d83d91 100644 (file)
--- a/drivers/s390/net/ism_drv.c
+++ b/drivers/s390/net/ism_drv.c
@@ -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) {