diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/Makefile.am | 1 | ||||
| -rw-r--r-- | doc/lchan-release.msc | 149 |
2 files changed, 150 insertions, 0 deletions
diff --git a/doc/Makefile.am b/doc/Makefile.am index cc2e277b5..3c8c2e0fa 100644 --- a/doc/Makefile.am +++ b/doc/Makefile.am @@ -5,6 +5,7 @@ SUBDIRS = \ msc: \ $(builddir)/handover.png \ $(builddir)/assignment.png \ + $(builddir)/lchan-release.png \ $(NULL) $(builddir)/%.png: $(srcdir)/%.msc diff --git a/doc/lchan-release.msc b/doc/lchan-release.msc new file mode 100644 index 000000000..f75b559c1 --- /dev/null +++ b/doc/lchan-release.msc @@ -0,0 +1,149 @@ +msc { + hscale=2; + ms [label="MS"], bts [label="BTS"], bsc[label="BSC"], bsc_gscon[label="BSC conn FSM"]; + + ms note bsc_gscon [label="various lchan release scenarios"]; + + + ms rbox bsc_gscon [label="IF BSC releases, from BSSMAP Clear Request"]; + bsc note bsc [label="lchan_release() may be called with sacch_deact=true or false. + Currently, the only time lchan_release(sacch_deact=true) is invoked is upon BSSMAP Clear + Command, i.e. when the MSC instructs to stop using an active lchan. + Some error handling code paths however directly invoke + rsl_rf_chan_release(error=1, SACCH_DEACTIVATE)."]; + + ---; + bsc_gscon note bsc_gscon [label="Rx: BSSMAP Clear Request from MSC"]; + bsc <- bsc_gscon [label="gsm0808_clear()"]; + bsc box bsc [label="lchan_release(sacch_deact=1)"]; + bsc box bsc [label="lchan->state = LCHAN_S_REL_REQ"]; + bsc box bsc [label="_lchan_handle_release(sacch_deact=1)"]; + bsc box bsc [label="rsl_release_sapis_from(start=1)"]; + bts <= bsc [label="RSL Release Request (Local End)..."]; + bts <= bsc [label="...for each SAPI, except link_id=0"]; + ms <= bsc [label="RR Channel Release"]; + ms note bsc [label="There is no ACK for RR Channel Release"]; + bsc box bsc [label="rsl_deact_sacch()"]; + bts <= bsc [label="RSL Deactivate SACCH"]; + bsc abox bsc [label="Start T3109 (net->T3109, t3109_expired())"]; + ...; + --- [label="If T3109 expires"]; + bsc box bsc [label="t3109_expired()"]; + bsc box bsc [label="rsl_rf_chan_release(error=1)"]; + bts <= bsc [label="RSL Release Request (Local End)..."]; + bts <= bsc [label="...for each SAPI, except link_id=0"]; + bsc box bsc [label="lchan->state = LCHAN_S_REL_REQ"]; + bts <= bsc [label="RSL RF Channel Release"]; + ---; + ...; + bsc rbox bsc [label="continue in the 'Common' part"]; + --- [label="END: 'BSSMAP Clear Request'"]; + ...; + ...; + + ms rbox bsc_gscon [label="IF BSC releases, from implicitly unused lchan"]; + bsc note bsc [label="The BSC may release old unused lchans after Handover, or release lchans + after some error condition."]; + bsc note bsc [label="BSC decides to release an unused lchan"]; + bsc box bsc [label="lchan_release(sacch_deact=0)"]; + bsc box bsc [label="lchan->state = LCHAN_S_REL_REQ"]; + bsc box bsc [label="_lchan_handle_release(sacch_deact=0)"]; + bts <= bsc [label="RSL Release Request (Local End)..."]; + bts <= bsc [label="...for all SAPIs"]; + ...; + bts note bsc_gscon [linecolor="red", + label="There seems to be no timer watching over RSL Release Request!"]; + ...; + bts => bsc [label="RSL Release Confirm..."]; + bts => bsc [label="...for all SAPIs"]; + bsc rbox bsc [label="continue in the 'Common' part"]; + ---; + ...; + ...; + + ms rbox bsc_gscon [label="IF MS releases"]; + ms => bts [label="DISC"]; + bts => bsc [label="RLL Release Ind..."]; + bts => bsc [label="...for each SAPI"]; + bsc rbox bsc [label="continue in the 'Common' part"]; + ---; + ...; + ...; + ms rbox bsc_gscon [label="Common"]; + --- [label="for each SAPI (?)"]; + bts => bsc [label="RLL Release Confirm / RLL Release Ind"]; + bsc box bsc [label="abis_rsl_rx_rll()"]; + bsc box bsc [label="mark lchan->sapis[link_id] = LCHAN_SAPI_UNUSED"]; + bsc box bsc [label="rll_indication()"]; + bsc box bsc [label="for each bsc_rll_req matching this link_id: + disable timer, call cb(BSC_RLLR_IND_REL_IND)"]; + bsc box bsc [label="rsl_handle_release()"]; + --- [label="IF all SAPIs are unused"]; + bsc box bsc [label="Stop T3109"]; + bsc note bsc [label="T3109 was started if the MSC requested the release"]; + bsc abox bsc [label="Start T3111 (net->T3111 value, t3111_expired())"]; + --- [label="END: all SAPIs are unused"]; + bsc -> bsc_gscon [label="GSCON_EV_RLL_REL_IND (only if RLL Release Ind)"]; + --- [label="END: for each SAPI"]; + + ...; + bsc box bsc [label="T3111 expires"]; + bsc box bsc [label="rsl_rf_chan_release()"]; + bsc box bsc [label="Stop T3109"]; + bsc note bsc [label="[If lchan->state is LCHAN_S_REL_ERR, don't do anything]"]; + bsc abox bsc [label="Start lchan->act_timer (4s, lchan_deact_tmr_cb())"]; + bts <= bsc [label="RSL RF Channel Release"]; + + ...; + --- [label="IF lchan->act_timer expires"]; + bsc box bsc [label="lchan_deact_tmr_cb()"]; + bsc box bsc [label="rsl_lchan_mark_broken(): lchan->state = LCHAN_S_BROKEN"]; + bsc box bsc [label="lchan_free() (see below)"]; + --- [label="END: 'lchan->act_timer expires'"]; + ...; + + bts => bsc [label="RSL RF Channel Release ACK"]; + bsc box bsc [label="rsl_rx_rf_chan_rel_ack()"]; + bsc box bsc [label="Stop lchan->act_timer"]; + bsc box bsc [label="Stop T3111"]; + + --- [label="IF lchan->state == LCHAN_S_BROKEN"]; + bsc note bsc [label="If an ACK comes in late, for specific BTS models, we may choose to 'repair' + the lchan so that it is usable again, by calling do_lchan_free() directly (see below)."]; + bsc box bsc [label="rsl_rx_rf_chan_rel_ack() exits here and none of below actions happen. + The lchan remains LCHAN_S_BROKEN indefinitely."]; + --- [label="END: lchan->state == LCHAN_S_BROKEN"]; + bsc box bsc [label="do_lchan_free()"]; + --- [label="IF lchan->state == LCHAN_S_REL_ERR"]; + bsc note bsc [label="If release failed, we take the lchan back into operation after due + timeout"]; + bsc abox bsc [label="Start lchan->error_timer (T3111+2, error_timeout_cb())"]; + bsc note bsc [label="do_lchan_free() continues, async:"]; + ...; + bsc box bsc [label="error_timeout_cb()"]; + bsc box bsc [label="lchan->state = LCHAN_S_NONE"]; + bsc box bsc [label="dyn TS: activate PDCH..."]; + --- [label="ELSE"]; + bsc box bsc [label="lchan->state = LCHAN_S_NONE"]; + --- [label="END: lchan->state == LCHAN_S_REL_ERR"]; + bsc box bsc [label="lchan_free()"]; + --- [label="IF conn is still associated (and not dyn TS in switchover)"]; + bsc -> bsc [label="S_LCHAN_UNEXPECTED_RELEASE"]; + bsc box bsc [label="handle_release()"]; + bsc box bsc [label="Stop T10"]; + bsc note bsc [linecolor=orange,label="conn->T10 is actually dead code, it is never started. + Instead, the conn FSM starts ST_WAIT_ASS_COMPL with a T10 value."]; + bsc -> bsc_gscon [label="GSCON_EV_RR_ASS_FAIL"]; + bsc -> bsc_gscon [label="GSCON_EV_TX_SCCP: BSSMAP Clear Request"]; + bsc box bsc [label="bsc_clear_handover()"]; + bsc box bsc [label="Stop T3103"]; + bsc box bsc [label="free handover struct"]; + bsc box bsc [label="lchan->conn = NULL"]; + --- [label="END: 'conn is still associated'"]; + bsc box bsc [label="Stop T3101"]; + bsc note bsc [label="T3101 is started when sending an RR Immediate Assignment"]; + bsc -> bsc [label="S_CHALLOC_FREED"]; + bsc -> bsc [label="rll_lchan_signal()"]; + bsc box bsc [label="for each bsc_rll_req matching this lchan: + disable timer, call cb(BSC_RLLR_IND_REL_IND)"]; +} |