Revert "Stop abusing T3169"

This reverts commit 846fd248dc.

The commit introduced a leak of UL-TBF, which do not time out and
accumulate indefinitely, leading to out-of-memory for the running
osmo-pcu process.

A proper fix for the leak is pending on a development branch pespin/fsm,
but that branch is not yet ready for merging. Hence let's re-introduce
timer T3169 to avoid the OOM due to lingering UL-TBF.

Related: OS#5209
Change-Id: I99a7d2ddf68a76739ce2db1d6a44967dd97667b0

src/bts.cpp

@@ -925,6 +925,7 @@ int bts_rcv_rach(struct gprs_rlcmac_bts *bts, const struct rach_ind_params *rip)
 			goto send_imm_ass_rej;
 		}
 		tbf->set_ta(ta);
+		T_START(tbf, T3169, 3169, "RACH (new UL-TBF)", true);
 		trx_no = tbf->trx->trx_no;
 		ts_no = tbf->first_ts;
 		usf = tbf->m_usf[ts_no];

src/tbf_ul.cpp

@@ -155,6 +155,7 @@ gprs_rlcmac_ul_tbf *tbf_alloc_ul_pacch(struct gprs_rlcmac_bts *bts, GprsMs *ms,
 	}
 	tbf->m_contention_resolution_done = 1;
 	TBF_SET_ASS_ON(tbf, GPRS_RLCMAC_FLAG_PACCH, false);
+	T_START(tbf, T3169, 3169, "allocation (UL-TBF)", true);
 	tbf->update_ms(tlli, GPRS_RLCMAC_UL_TBF);
 	OSMO_ASSERT(tbf->ms());
 
@@ -413,6 +414,9 @@ int gprs_rlcmac_ul_tbf::rcv_data_block_acknowledged(
 	uint32_t new_tlli = GSM_RESERVED_TMSI;
 	unsigned int block_idx;
 
+	/* restart T3169 */
+	T_START(this, T3169, 3169, "acked (data)", true);
+
 	/* Increment RX-counter */
 	this->m_rx_counter++;
 	update_coding_scheme_counter_ul(rlc->cs);