diff --git a/libraries/rtos/rtos/Thread.cpp b/libraries/rtos/rtos/Thread.cpp
index ed8270a36a..3af476ce60 100644
--- a/libraries/rtos/rtos/Thread.cpp
+++ b/libraries/rtos/rtos/Thread.cpp
@@ -24,6 +24,12 @@
 #include "mbed_error.h"
 #include "rtos_idle.h"
 
+// rt_tid2ptcb is an internal function which we exposed to get TCB for thread id
+#undef NULL  //Workaround for conflicting macros in rt_TypeDef.h and stdio.h
+#include "rt_TypeDef.h"
+
+extern "C" P_TCB rt_tid2ptcb(osThreadId thread_id);
+
 namespace rtos {
 
 Thread::Thread(void (*task)(void const *argument), void *argument,
@@ -87,7 +93,8 @@ uint32_t Thread::stack_size() {
 #if defined(CMSIS_OS_RTX) && !defined(__MBED_CMSIS_RTOS_CM)
     return _thread_def.tcb.priv_stack;
 #else
-    return 0;
+    P_TCB tcb = rt_tid2ptcb(_tid);
+    return tcb->priv_stack;
 #endif
 #else
     return 0;
@@ -100,7 +107,9 @@ uint32_t Thread::free_stack() {
     uint32_t bottom = (uint32_t)_thread_def.tcb.stack;
     return _thread_def.tcb.tsk_stack - bottom;
 #else
-    return 0;
+    P_TCB tcb = rt_tid2ptcb(_tid);
+    uint32_t bottom = (uint32_t)tcb->stack;
+    return tcb->tsk_stack - bottom;
 #endif
 #else
     return 0;
@@ -113,7 +122,9 @@ uint32_t Thread::used_stack() {
     uint32_t top = (uint32_t)_thread_def.tcb.stack + _thread_def.tcb.priv_stack;
     return top - _thread_def.tcb.tsk_stack;
 #else
-    return 0;
+    P_TCB tcb = rt_tid2ptcb(_tid);
+    uint32_t top = (uint32_t)tcb->stack + tcb->priv_stack;
+    return top - tcb->tsk_stack;
 #endif
 #else
     return 0;
@@ -128,7 +139,11 @@ uint32_t Thread::max_stack() {
         high_mark++;
     return _thread_def.tcb.priv_stack - (high_mark * 4);
 #else
-    return 0;
+    P_TCB tcb = rt_tid2ptcb(_tid);
+    uint32_t high_mark = 0;
+    while (tcb->stack[high_mark] == 0xE25A2EA5)
+        high_mark++;
+    return tcb->priv_stack - (high_mark * 4);
 #endif
 #else
     return 0;
diff --git a/libraries/rtos/rtx/TARGET_CORTEX_M/rt_CMSIS.c b/libraries/rtos/rtx/TARGET_CORTEX_M/rt_CMSIS.c
index d76eb89242..057fced7e3 100644
--- a/libraries/rtos/rtx/TARGET_CORTEX_M/rt_CMSIS.c
+++ b/libraries/rtos/rtx/TARGET_CORTEX_M/rt_CMSIS.c
@@ -407,7 +407,7 @@ static uint16_t rt_ms2tick (uint32_t millisec) {
 }
 
 /// Convert Thread ID to TCB pointer
-static P_TCB rt_tid2ptcb (osThreadId thread_id) {
+P_TCB rt_tid2ptcb (osThreadId thread_id) {
   P_TCB ptcb;
 
   if (thread_id == NULL) { return NULL; }
@@ -506,8 +506,8 @@ osStatus svcKernelStart (void) {
   if (os_tsk.run->task_id == 0xFFU) {           // Idle Thread
     __set_PSP(os_tsk.run->tsk_stack + (8U*4U)); // Setup PSP
   }
-  if (os_tsk.new == NULL) {                     // Force context switch
-    os_tsk.new = os_tsk.run;
+  if (os_tsk.new_tsk == NULL) {                     // Force context switch
+    os_tsk.new_tsk = os_tsk.run;
     os_tsk.run = NULL;
   }
 
diff --git a/libraries/rtos/rtx/TARGET_CORTEX_M/rt_HAL_CM.h b/libraries/rtos/rtx/TARGET_CORTEX_M/rt_HAL_CM.h
index 151eb2f771..d6bac9a0db 100644
--- a/libraries/rtos/rtx/TARGET_CORTEX_M/rt_HAL_CM.h
+++ b/libraries/rtos/rtx/TARGET_CORTEX_M/rt_HAL_CM.h
@@ -276,7 +276,7 @@ extern void dbg_task_switch (U32 task_id);
 #ifdef DBG_MSG
 #define DBG_INIT() dbg_init()
 #define DBG_TASK_NOTIFY(p_tcb,create) if (dbg_msg) dbg_task_notify(p_tcb,create)
-#define DBG_TASK_SWITCH(task_id)      if (dbg_msg && (os_tsk.new!=os_tsk.run)) \
+#define DBG_TASK_SWITCH(task_id)      if (dbg_msg && (os_tsk.new_tsk!=os_tsk.run)) \
                                         dbg_task_switch(task_id)
 #else
 #define DBG_INIT()
diff --git a/libraries/rtos/rtx/TARGET_CORTEX_M/rt_Task.c b/libraries/rtos/rtx/TARGET_CORTEX_M/rt_Task.c
index 73356b663d..17a3da04cf 100644
--- a/libraries/rtos/rtx/TARGET_CORTEX_M/rt_Task.c
+++ b/libraries/rtos/rtx/TARGET_CORTEX_M/rt_Task.c
@@ -99,7 +99,7 @@ static void rt_init_context (P_TCB p_TCB, U8 priority, FUNCP task_body) {
 
 void rt_switch_req (P_TCB p_new) {
   /* Switch to next task (identified by "p_new"). */
-  os_tsk.new   = p_new;
+  os_tsk.new_tsk   = p_new;
   p_new->state = RUNNING;
   DBG_TASK_SWITCH(p_new->task_id);
 }
diff --git a/libraries/rtos/rtx/TARGET_CORTEX_M/rt_TypeDef.h b/libraries/rtos/rtx/TARGET_CORTEX_M/rt_TypeDef.h
index a3e7677239..86a84d2750 100644
--- a/libraries/rtos/rtx/TARGET_CORTEX_M/rt_TypeDef.h
+++ b/libraries/rtos/rtx/TARGET_CORTEX_M/rt_TypeDef.h
@@ -98,7 +98,7 @@ typedef struct OS_PSQ {           /* Post Service Queue                      */
 
 typedef struct OS_TSK {
   P_TCB  run;                     /* Current running task                    */
-  P_TCB  new;                     /* Scheduled task to run                   */
+  P_TCB  new_tsk;                /* Scheduled task to run                   */
 } *P_TSK;
 
 typedef struct OS_ROBIN {         /* Round Robin Control                     */