diff --git a/common/utils/LOG/log.c b/common/utils/LOG/log.c
index acd4b8c437..d856a2cfe6 100644
--- a/common/utils/LOG/log.c
+++ b/common/utils/LOG/log.c
@@ -479,6 +479,7 @@ char *log_getthreadname(char *threadname,
 }
 
 #if LOG_MINIMAL
+#include <sys/syscall.h>
 void logMinimal(int comp, int level, const char *format, ...)
 {
     struct timespec ts;
@@ -486,9 +487,10 @@ void logMinimal(int comp, int level, const char *format, ...)
         abort();
 
     char buf[MAX_LOG_TOTAL];
-    int n = snprintf(buf, sizeof(buf), "%lu.%06lu [%s] %c ",
+    int n = snprintf(buf, sizeof(buf), "%lu.%06lu %08lx [%s] %c ",
                      ts.tv_sec,
                      ts.tv_nsec / 1000,
+                     syscall(__NR_gettid),
                      g_log->log_component[comp].name,
                      level);
     if (n < 0 || n >= sizeof(buf))
diff --git a/openair2/LAYER2/MAC/main_ue.c b/openair2/LAYER2/MAC/main_ue.c
index 2868d94930..bbb9acdaf1 100644
--- a/openair2/LAYER2/MAC/main_ue.c
+++ b/openair2/LAYER2/MAC/main_ue.c
@@ -41,9 +41,9 @@
 #include "common/utils/LOG/log.h"
 #include "nfapi/oai_integration/vendor_ext.h"
 #include "RRC/L2_INTERFACE/openair_rrc_L2_interface.h"
-
-
+#include "PHY_INTERFACE/phy_stub_UE.h"
 #include "common/ran_context.h"
+
 extern void openair_rrc_top_init_ue( int eMBMS_active, char *uecap_xer, uint8_t cba_group_active, uint8_t HO_active);
 
 void dl_phy_sync_success(module_id_t module_idP, frame_t frameP, unsigned char eNB_index, uint8_t first_sync) { //init as MR
@@ -89,6 +89,16 @@ mac_top_init_ue(int eMBMS_active, char *uecap_xer,
     UE_mac_inst = NULL;
   }
 
+  // mutex below are used for multiple UE's L2 FAPI simulation.
+  if (NFAPI_MODE == NFAPI_UE_STUB_PNF || NFAPI_MODE == NFAPI_MODE_STANDALONE_PNF) {
+    pthread_mutex_init(&fill_ul_mutex.rx_mutex,NULL);
+    pthread_mutex_init(&fill_ul_mutex.crc_mutex,NULL);
+    pthread_mutex_init(&fill_ul_mutex.sr_mutex,NULL);
+    pthread_mutex_init(&fill_ul_mutex.harq_mutex,NULL);
+    pthread_mutex_init(&fill_ul_mutex.cqi_mutex,NULL);
+    pthread_mutex_init(&fill_ul_mutex.rach_mutex,NULL);
+  }
+
   LOG_I(MAC, "[MAIN] calling RRC\n");
   openair_rrc_top_init_ue(eMBMS_active, uecap_xer, cba_group_active,
                           HO_active);
diff --git a/openair2/PHY_INTERFACE/phy_stub_UE.c b/openair2/PHY_INTERFACE/phy_stub_UE.c
index e1b6d3e332..c3e6764165 100644
--- a/openair2/PHY_INTERFACE/phy_stub_UE.c
+++ b/openair2/PHY_INTERFACE/phy_stub_UE.c
@@ -47,6 +47,8 @@ queue_t dl_config_req_tx_req_queue;
 queue_t ul_config_req_queue;
 queue_t hi_dci0_req_queue;
 
+FILL_UL_INFO_MUTEX_t fill_ul_mutex;
+
 int current_sfn_sf;
 sem_t sfn_semaphore;
 
@@ -114,6 +116,8 @@ void fill_rx_indication_UE_MAC(module_id_t Mod_id,
 
   UL_INFO->rx_ind.rx_indication_body.number_of_pdus++;
   UL_INFO->rx_ind.sfn_sf = frame << 4 | subframe;
+
+  pthread_mutex_unlock(&fill_ul_mutex.rx_mutex);
 }
 
 void fill_sr_indication_UE_MAC(int Mod_id,
@@ -152,6 +156,8 @@ void fill_sr_indication_UE_MAC(int Mod_id,
 
   // UL_INFO->rx_ind.rx_indication_body.number_of_pdus++;
   sr_ind_body->number_of_srs++;
+
+  pthread_mutex_unlock(&fill_ul_mutex.sr_mutex);
 }
 
 void fill_crc_indication_UE_MAC(int Mod_id,
@@ -188,6 +194,8 @@ void fill_crc_indication_UE_MAC(int Mod_id,
         __FUNCTION__,
         pdu->rx_ue_information.rnti,
         UL_INFO->crc_ind.crc_indication_body.number_of_crcs);
+
+  pthread_mutex_unlock(&fill_ul_mutex.crc_mutex);
 }
 
 void fill_rach_indication_UE_MAC(int Mod_id,
@@ -196,6 +204,8 @@ void fill_rach_indication_UE_MAC(int Mod_id,
                                  UL_IND_t *UL_INFO,
                                  uint8_t ra_PreambleIndex,
                                  uint16_t ra_RNTI) {
+  pthread_mutex_lock(&fill_ul_mutex.rach_mutex);
+
   UL_INFO->rach_ind.rach_indication_body.number_of_preambles = 1;
 
   UL_INFO->rach_ind.header.message_id = NFAPI_RACH_INDICATION;
@@ -245,6 +255,8 @@ void fill_rach_indication_UE_MAC(int Mod_id,
   }
 
   free(UL_INFO->rach_ind.rach_indication_body.preamble_list);
+
+  pthread_mutex_unlock(&fill_ul_mutex.rach_mutex);
 }
 
 void fill_ulsch_cqi_indication_UE_MAC(int Mod_id,
@@ -333,6 +345,8 @@ void fill_ulsch_harq_indication_UE_MAC(
   }
 
   UL_INFO->harq_ind.harq_indication_body.number_of_harqs++;
+
+  pthread_mutex_unlock(&fill_ul_mutex.harq_mutex);
 }
 
 void fill_uci_harq_indication_UE_MAC(int Mod_id,
@@ -425,6 +439,8 @@ void fill_uci_harq_indication_UE_MAC(int Mod_id,
   LOG_D(PHY,
         "Incremented eNB->UL_INFO.harq_ind.number_of_harqs:%d\n",
         UL_INFO->harq_ind.harq_indication_body.number_of_harqs);
+
+  pthread_mutex_unlock(&fill_ul_mutex.harq_mutex);
 }
 
 void handle_nfapi_ul_pdu_UE_MAC(module_id_t Mod_id,
diff --git a/openair2/PHY_INTERFACE/phy_stub_UE.h b/openair2/PHY_INTERFACE/phy_stub_UE.h
index 6eb339cb9e..e6c74be3f5 100644
--- a/openair2/PHY_INTERFACE/phy_stub_UE.h
+++ b/openair2/PHY_INTERFACE/phy_stub_UE.h
@@ -22,7 +22,7 @@
 #include "queue.h"
 
 // this mutex is used to set multiple UE's UL value in L2 FAPI simulator.
-FILL_UL_INFO_MUTEX_t fill_ul_mutex;
+extern FILL_UL_INFO_MUTEX_t fill_ul_mutex;
 //below 2 difinitions move to phy_stub_UE.c to add initialization when difinition.
 extern UL_IND_t *UL_INFO;
 // New