diff --git a/sched/sched/sched_lock.c b/sched/sched/sched_lock.c
index d07e751b994..f0400b57dc2 100644
--- a/sched/sched/sched_lock.c
+++ b/sched/sched/sched_lock.c
@@ -148,13 +148,15 @@ int sched_lock(void)
 
   if (rtcb != NULL && !up_interrupt_context())
     {
+      irqstate_t flags;
+
       /* Catch attempts to increment the lockcount beyond the range of the
        * integer type.
        */
 
       DEBUGASSERT(rtcb->lockcount < MAX_LOCK_COUNT);
 
-      irqstate_t flags = enter_critical_section();
+      flags = enter_critical_section();
 
       /* We must hold the lock on this CPU before we increment the lockcount
        * for the first time. Holding the lock is sufficient to lockout
@@ -234,12 +236,17 @@ int sched_lock(void)
 
   if (rtcb != NULL && !up_interrupt_context())
     {
+      FAR struct tcb_s *ptcb;
+      irqstate_t flags;
+
       /* Catch attempts to increment the lockcount beyond the range of the
        * integer type.
        */
 
       DEBUGASSERT(rtcb->lockcount < MAX_LOCK_COUNT);
 
+      flags = enter_critical_section();
+
       /* A counter is used to support locking.  This allows nested lock
        * operations on this thread (on any CPU)
        */
@@ -262,6 +269,22 @@ int sched_lock(void)
 #endif
         }
 #endif
+
+      /* Move any tasks in the ready-to-run list to the pending task list
+       * where they will not be available to run until the scheduler is
+       * unlocked and nxsched_merge_pending() is called.  So ready-to-run
+       * will consist only from the currently runnig task and the idle task.
+       */
+
+      for (ptcb = rtcb->flink; ptcb && ptcb->flink; ptcb = rtcb->flink)
+        {
+          dq_rem((FAR dq_entry_t *)ptcb, &g_readytorun);
+
+          nxsched_add_prioritized(ptcb, &g_pendingtasks);
+          ptcb->task_state = TSTATE_TASK_PENDING;
+        }
+
+      leave_critical_section(flags);
     }
 
   return OK;
diff --git a/sched/sched/sched_mergepending.c b/sched/sched/sched_mergepending.c
index 5c30d3ca6c7..9915eb3abde 100644
--- a/sched/sched/sched_mergepending.c
+++ b/sched/sched/sched_mergepending.c
@@ -82,73 +82,79 @@ bool nxsched_merge_pending(void)
 
   rtcb = this_task();
 
-  /* Process every TCB in the g_pendingtasks list */
+  /* Process every TCB in the g_pendingtasks list
+   *
+   * Do nothing if pre-emption is still disabled
+   */
 
-  for (ptcb = (FAR struct tcb_s *)g_pendingtasks.head;
-       ptcb;
-       ptcb = pnext)
+  if (rtcb->lockcount == 0)
     {
-      pnext = ptcb->flink;
-
-      /* REVISIT:  Why don't we just remove the ptcb from pending task list
-       * and call nxsched_add_readytorun?
-       */
-
-      /* Search the ready-to-run list to find the location to insert the
-       * new ptcb. Each is list is maintained in ascending sched_priority
-       * order.
-       */
-
-      for (;
-           (rtcb && ptcb->sched_priority <= rtcb->sched_priority);
-           rtcb = rtcb->flink)
+      for (ptcb = (FAR struct tcb_s *)g_pendingtasks.head;
+           ptcb;
+           ptcb = pnext)
         {
+          pnext = ptcb->flink;
+
+          /* REVISIT:  Why don't we just remove the ptcb from pending task
+           * list and call nxsched_add_readytorun?
+           */
+
+          /* Search the ready-to-run list to find the location to insert the
+           * new ptcb. Each is list is maintained in ascending sched_priority
+           * order.
+           */
+
+          for (;
+               (rtcb && ptcb->sched_priority <= rtcb->sched_priority);
+               rtcb = rtcb->flink)
+            {
+            }
+
+          /* Add the ptcb to the spot found in the list.  Check if the
+           * ptcb goes at the ends of the ready-to-run list. This would be
+           * error condition since the idle test must always be at the end of
+           * the ready-to-run list!
+           */
+
+          DEBUGASSERT(rtcb);
+
+          /* The ptcb goes just before rtcb */
+
+          rprev = rtcb->blink;
+          if (rprev == NULL)
+            {
+              /* Special case: Inserting ptcb at the head of the list */
+
+              ptcb->flink       = rtcb;
+              ptcb->blink       = NULL;
+              rtcb->blink       = ptcb;
+              g_readytorun.head = (FAR dq_entry_t *)ptcb;
+              rtcb->task_state  = TSTATE_TASK_READYTORUN;
+              ptcb->task_state  = TSTATE_TASK_RUNNING;
+              ret               = true;
+            }
+          else
+            {
+              /* Insert in the middle of the list */
+
+              ptcb->flink       = rtcb;
+              ptcb->blink       = rprev;
+              rprev->flink      = ptcb;
+              rtcb->blink       = ptcb;
+              ptcb->task_state  = TSTATE_TASK_READYTORUN;
+            }
+
+          /* Set up for the next time through */
+
+          rtcb = ptcb;
         }
 
-      /* Add the ptcb to the spot found in the list.  Check if the
-       * ptcb goes at the ends of the ready-to-run list. This would be
-       * error condition since the idle test must always be at the end of
-       * the ready-to-run list!
-       */
+      /* Mark the input list empty */
 
-      DEBUGASSERT(rtcb);
-
-      /* The ptcb goes just before rtcb */
-
-      rprev = rtcb->blink;
-      if (rprev == NULL)
-        {
-          /* Special case: Inserting ptcb at the head of the list */
-
-          ptcb->flink       = rtcb;
-          ptcb->blink       = NULL;
-          rtcb->blink       = ptcb;
-          g_readytorun.head = (FAR dq_entry_t *)ptcb;
-          rtcb->task_state  = TSTATE_TASK_READYTORUN;
-          ptcb->task_state  = TSTATE_TASK_RUNNING;
-          ret               = true;
-        }
-      else
-        {
-          /* Insert in the middle of the list */
-
-          ptcb->flink       = rtcb;
-          ptcb->blink       = rprev;
-          rprev->flink      = ptcb;
-          rtcb->blink       = ptcb;
-          ptcb->task_state  = TSTATE_TASK_READYTORUN;
-        }
-
-      /* Set up for the next time through */
-
-      rtcb = ptcb;
+      g_pendingtasks.head = NULL;
+      g_pendingtasks.tail = NULL;
     }
 
-  /* Mark the input list empty */
-
-  g_pendingtasks.head = NULL;
-  g_pendingtasks.tail = NULL;
-
   return ret;
 }
 #endif /* !CONFIG_SMP */