IB/qib: Limit the number of packets processed per interrupt

Don't processes too many packets without allowing other IRQ functions
a chance to run. Otherwise, there is a chance of getting a "soft
lockup" messages and poor application response times.

Signed-off-by: Ralph Campbell <ralph.campbell@qlogic.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/hw/qib/qib_driver.c

@@ -335,7 +335,7 @@ u32 qib_kreceive(struct qib_ctxtdata *rcd, u32 *llic, u32 *npkts)
 		smp_rmb();  /* prevent speculative reads of dma'ed hdrq */
 	}
 
-	for (last = 0, i = 1; !last; i += !last) {
+	for (last = 0, i = 1; !last && i <= 64; i += !last) {
 		hdr = dd->f_get_msgheader(dd, rhf_addr);
 		eflags = qib_hdrget_err_flags(rhf_addr);
 		etype = qib_hdrget_rcv_type(rhf_addr);