diff --git a/sched/irq/irq_csection.c b/sched/irq/irq_csection.c
index a03c090e63..8071da9758 100644
--- a/sched/irq/irq_csection.c
+++ b/sched/irq/irq_csection.c
@@ -263,6 +263,12 @@ irqstate_t enter_critical_section(void)
 #else /* defined(CONFIG_SCHED_INSTRUMENTATION_CSECTION) */
 irqstate_t enter_critical_section(void)
 {
+  irqstate_t ret;
+
+  /* Disable interrupts */
+
+  ret = up_irq_save();
+
   /* Check if we were called from an interrupt handler and that the task
    * lists have been initialized.
    */
@@ -272,14 +278,14 @@ irqstate_t enter_critical_section(void)
       FAR struct tcb_s *rtcb = this_task();
       DEBUGASSERT(rtcb != NULL);
 
-      /* No.. note that we have entered the critical section */
+      /* Yes.. Note that we have entered the critical section */
 
       sched_note_csection(rtcb, true);
     }
 
-  /* And disable interrupts */
+  /* Return interrupt status */
 
-  return up_irq_save();
+  return ret;
 }
 #endif
 
@@ -386,9 +392,10 @@ void leave_critical_section(irqstate_t flags)
                   /* Check if there are pending tasks and that pre-emption
                    * is also enabled.
                    *
-                   * REVISIT: There is an issue here!  up_release_pending()
+                   * REVISIT: Is there an issue here?  up_release_pending()
                    * must be called from within a critical section but here
-                   * we have just left the critical section.
+                   * we have just left the critical section.  At least we
+                   * still have interrupts disabled on this CPU.
                    */
 
                   if (g_pendingtasks.head != NULL &&
@@ -429,7 +436,7 @@ void leave_critical_section(irqstate_t flags)
       FAR struct tcb_s *rtcb = this_task();
       DEBUGASSERT(rtcb != NULL);
 
-      /* Note that we have left the critical section */
+      /* Yes.. Note that we have left the critical section */
 
       sched_note_csection(rtcb, false);
     }
diff --git a/sched/wdog/wd_start.c b/sched/wdog/wd_start.c
index 898f80060f..149b95427e 100644
--- a/sched/wdog/wd_start.c
+++ b/sched/wdog/wd_start.c
@@ -421,11 +421,28 @@ int wd_start(WDOG_ID wdog, int32_t delay, wdentry_t wdentry,  int argc, ...)
 unsigned int wd_timer(int ticks)
 {
   FAR struct wdog_s *wdog;
+#ifdef CONFIG_SMP
+  irqstate_t flags;
+#endif
+  unsigned int ret;
   int decr;
 
+#ifdef CONFIG_SMP
+  /* We are in an interrupt handler as, as a consequence, interrupts are
+   * disabled.  But in the SMP case, interrupst MAY be disabled only on
+   * the local CPU since most architectures do not permit disabling
+   * interrupts on other CPUS.
+   *
+   * Hence, we must follow rules for critical sections even here in the
+   * SMP case.
+   */
+
+  flags = enter_critical_section();
+#endif
+
   /* Check if there are any active watchdogs to process */
 
-  while (g_wdactivelist.head && ticks > 0)
+  while (g_wdactivelist.head != NULL && ticks > 0)
     {
       /* Get the watchdog at the head of the list */
 
@@ -455,13 +472,36 @@ unsigned int wd_timer(int ticks)
 
   /* Return the delay for the next watchdog to expire */
 
-  return g_wdactivelist.head ?
-         ((FAR struct wdog_s *)g_wdactivelist.head)->lag : 0;
+  ret = g_wdactivelist.head ?
+          ((FAR struct wdog_s *)g_wdactivelist.head)->lag : 0;
+
+#ifdef CONFIG_SMP
+  leave_critical_section(flags);
+#endif
+
+  /* Return the delay for the next watchdog to expire */
+
+  return ret;
 }
 
 #else
 void wd_timer(void)
 {
+#ifdef CONFIG_SMP
+  irqstate_t flags;
+
+  /* We are in an interrupt handler as, as a consequence, interrupts are
+   * disabled.  But in the SMP case, interrupst MAY be disabled only on
+   * the local CPU since most architectures do not permit disabling
+   * interrupts on other CPUS.
+   *
+   * Hence, we must follow rules for critical sections even here in the
+   * SMP case.
+   */
+
+  flags = enter_critical_section();
+#endif
+
   /* Check if there are any active watchdogs to process */
 
   if (g_wdactivelist.head)
@@ -474,5 +514,9 @@ void wd_timer(void)
 
       wd_expiration();
     }
+
+#ifdef CONFIG_SMP
+  leave_critical_section(flags);
+#endif
 }
 #endif /* CONFIG_SCHED_TICKLESS */