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Introduce UE release request grace period

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It might happen that the CU does not answer a release request. In that
case, the MAC would never free the UE context, potentially blocking the
DU. Avoid this by introducing a "grace period" after which a UE context
is automatically freed at the MAC (and RLC), currently at 10s after the
30s UL failure timer.
This commit is contained in:
Robert Schmidt
2025-07-04 09:40:26 +02:00
parent 67e9c9c263
commit 2ea3ab5050
2 changed files with 25 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
openair2/LAYER2/NR_MAC_gNB/gNB_scheduler_primitives.c
+24 -9
View File
@@ -3167,7 +3167,12 @@ void nr_mac_update_timers(module_id_t module_id, frame_t frame, slot_t slot)
}
/* check if UL failure and trigger release request if necessary */
nr_mac_check_ul_failure(mac, UE->rnti, sched_ctrl);
bool released = nr_mac_check_ul_failure(mac, UE->rnti, sched_ctrl);
if (released) {
// go back to examine the next UE, which is at the position the current UE was
UE--;
continue;
}
if (nr_timer_tick(&sched_ctrl->transm_interrupt)) {
/* expired */
@@ -3360,6 +3365,8 @@ bool nr_mac_check_release(NR_UE_sched_ctrl_t *sched_ctrl, int rnti)
return sched_ctrl->release_timer == 0;
}
#define UL_FAILURE_REQ_GRACE 10000
#define UL_FAILURE_TIMEOUT 30000
void nr_mac_trigger_ul_failure(NR_UE_sched_ctrl_t *sched_ctrl, NR_SubcarrierSpacing_t subcarrier_spacing)
{
if (sched_ctrl->ul_failure) {
@@ -3367,8 +3374,9 @@ void nr_mac_trigger_ul_failure(NR_UE_sched_ctrl_t *sched_ctrl, NR_SubcarrierSpac
return;
}
sched_ctrl->ul_failure = true;
// 30 seconds till triggering release request
sched_ctrl->ul_failure_timer = 30000 << subcarrier_spacing;
// UL_FAILURE_TIMEOUT ms till triggering release request
// UL_FAILURE_REQ_GRACE ms till automatically released after request
sched_ctrl->ul_failure_timer = (UL_FAILURE_REQ_GRACE + UL_FAILURE_TIMEOUT) << subcarrier_spacing;
}
void nr_mac_reset_ul_failure(NR_UE_sched_ctrl_t *sched_ctrl)
@@ -3398,20 +3406,27 @@ bool nr_mac_request_release_ue(const gNB_MAC_INST *nrmac, int rnti)
return true;
}
void nr_mac_check_ul_failure(gNB_MAC_INST *nrmac, int rnti, NR_UE_sched_ctrl_t *sched_ctrl)
bool nr_mac_check_ul_failure(gNB_MAC_INST *nrmac, int rnti, NR_UE_sched_ctrl_t *sched_ctrl)
{
if (!sched_ctrl->ul_failure)
return;
return false;
if (sched_ctrl->ul_failure_timer > 0)
sched_ctrl->ul_failure_timer--;
/* to trigger only once: trigger when ul_failure_timer == 1, but timer will
* stop at 0 and we wait for a UE release command from upper layers */
if (sched_ctrl->ul_failure_timer == 1) {
/* trigger once: trigger when ul_failure_timer == UL_FAILURE_REQ_GRACE( we
* wait for a UE release command from upper layers), and UE is automatically
* released when no answer after UL_FAILURE_REQ_GRACE */
if (sched_ctrl->ul_failure_timer == UL_FAILURE_REQ_GRACE) {
LOG_W(MAC, "UE %04x: request release after UL failure timer expiry\n", rnti);
bool requested = nr_mac_request_release_ue(nrmac, rnti);
if (!requested)
nr_mac_release_ue(nrmac, rnti);
sched_ctrl->ul_failure_timer = 0; /* force expiry */
}
if (sched_ctrl->ul_failure_timer == 0) {
LOG_W(NR_MAC, "UE %04x: no answer for release request, dropping UE\n", rnti);
nr_mac_release_ue(nrmac, rnti);
return true;
}
return false;
}
void nr_mac_trigger_reconfiguration(const gNB_MAC_INST *nrmac, const NR_UE_info_t *UE)