chan_alloc: Change Channel Release to release SAPIs, then the channel
Currently every SAPI release indication will trigger the channel. It
was possible that we had SAPI=3 and SAPI=0 allocated and we tried to
release the channel by sending a RF Channel Release, the BTS answered
with a RF Channel Release ACK but also sent the SAPI Release Indication
which triggered a channel release here. So it was possible that we
would have released a newly allocated channel because of the SAPI
release of the old connection.
This code now works by releasing all SAPIs from highest to lowest,
then sending a SACH Deactivate and finally releasing the channel. This
approach is in use on the on-waves/bsc-master.
diff --git a/openbsc/src/abis_rsl.c b/openbsc/src/abis_rsl.c
index 7b19d7f..7068422 100644
--- a/openbsc/src/abis_rsl.c
+++ b/openbsc/src/abis_rsl.c
@@ -1356,11 +1356,21 @@
static void rsl_handle_release(struct gsm_lchan *lchan)
{
+ int sapi;
struct gsm_bts *bts;
+
+ /* maybe we have only brought down one RLL */
if (lchan->state != LCHAN_S_REL_REQ)
- LOGP(DRSL, LOGL_ERROR, "RF release on %s but state %s\n",
- gsm_lchan_name(lchan),
- gsm_lchans_name(lchan->state));
+ return;
+
+ for (sapi = 0; sapi < ARRAY_SIZE(lchan->sapis); ++sapi) {
+ if (lchan->sapis[sapi] == LCHAN_SAPI_UNUSED)
+ continue;
+ LOGP(DRSL, LOGL_NOTICE, "%s waiting for SAPI=%d to be released.\n",
+ gsm_lchan_name(lchan), sapi);
+ return;
+ }
+
/* wait a bit to send the RF Channel Release */
@@ -1422,6 +1432,7 @@
rll_indication(msg->lchan, rllh->link_id,
BSC_RLLR_IND_REL_IND);
rsl_handle_release(msg->lchan);
+ rsl_lchan_rll_release(msg->lchan, rllh->link_id);
break;
case RSL_MT_REL_CONF:
/* BTS informs us of having received UA from MS,
@@ -1429,6 +1440,7 @@
DEBUGPC(DRLL, "RELEASE CONFIRMATION\n");
msg->lchan->sapis[rllh->link_id & 0x7] = LCHAN_SAPI_UNUSED;
rsl_handle_release(msg->lchan);
+ rsl_lchan_rll_release(msg->lchan, rllh->link_id);
break;
case RSL_MT_ERROR_IND:
rc = rsl_rx_rll_err_ind(msg);