alloc: Skip common TS without free USF when rating

Currently the search of the "best" slot combination is done
separately from the UL slot selection, which can lead to an
allocation failure due to USF exhaustion even if another combination
had been possible.

This commit reduces the probability for this event by skipping UL
slots without free USF while calculation the capacity.

Note that the implementation is rather inefficient which will be
fixed by the following commits.

Sponsored-by: On-Waves ehf

1 files changed, 5 insertions, 3 deletions

diff --git a/src/gprs_rlcmac_ts_alloc.cpp b/src/gprs_rlcmac_ts_alloc.cpp
index 338362c6..1819b5b5 100644
--- a/src/gprs_rlcmac_ts_alloc.cpp
+++ b/src/gprs_rlcmac_ts_alloc.cpp
@@ -551,9 +551,11 @@ static int find_multi_slots(struct gprs_rlcmac_bts *bts,
 			}
 			/* Only consider common slots for UL */
 			if (tx_window & rx_window & (1 << ts)) {
-				c = 32 - pdch->num_reserved(GPRS_RLCMAC_UL_TBF);
-				c = OSMO_MAX(c, 1);
-				capacity += c;
+				if (find_free_usf(pdch) >= 0) {
+					c = 32 - pdch->num_reserved(GPRS_RLCMAC_UL_TBF);
+					c = OSMO_MAX(c, 1);
+					capacity += c;
+				}
 			}
 		}