arch/: Relasted to last big change to force interrupts to be disabled. In the SMP case, we still must call leave_critical_section() at least once in order to compensate for the fact that the irqcount was incremented in up_schedsigaction().

arch/arm/src/armv7-a/arm_schedulesigaction.c

@@ -121,7 +121,9 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
 
           if (!CURRENT_REGS)
             {
-              /* In this case just deliver the signal now. */
+              /* In this case just deliver the signal now.
+               * REVISIT:  Signal handler will run in a critical section!
+               */
 
               sigdeliver(tcb);
             }
@@ -227,7 +229,9 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
 
           if (cpu == me && !CURRENT_REGS)
             {
-              /* In this case just deliver the signal now. */
+              /* In this case just deliver the signal now.
+               * REVISIT:  Signal handler will run in a critical section!
+               */
 
               sigdeliver(tcb);
             }

arch/arm/src/armv7-a/arm_sigdeliver.c

@@ -101,9 +101,24 @@ void up_sigdeliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
+#ifdef CONFIG_SMP
+  /* In the SMP case, up_schedule_sigaction(0) will have incremented
+   * 'irqcount' in order to force us into a critical section.  At a minimum,
+   * we must call leave_critical_section() at least once in order to
+   * compensate for that.
+   */
+
+  leave_critical_section(regs[REG_CPSR]);
+#endif /* CONFIG_SMP */
+
 #ifndef CONFIG_SUPPRESS_INTERRUPTS
   /* Then make sure that interrupts are enabled.  Signal handlers must always
    * run with interrupts enabled.
+   *
+   * REVISIT: 'irqcount' could still be greater than zero in the SMP case.
+   * This would be an issue if the signal handler were to suspend because
+   * the critical section would be re-established when the signal handler
+   * resumes.
    */
 
   up_irq_enable();

arch/arm/src/armv7-m/up_schedulesigaction.c

@@ -123,7 +123,9 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
 
           if (!CURRENT_REGS)
             {
-              /* In this case just deliver the signal now. */
+              /* In this case just deliver the signal now.
+               * REVISIT:  Signal handle will run in a critical section!
+               */
 
               sigdeliver(tcb);
             }
@@ -255,7 +257,9 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
 
           if (cpu == me && !CURRENT_REGS)
             {
-              /* In this case just deliver the signal now. */
+              /* In this case just deliver the signal now.
+               * REVISIT:  Signal handler will run in a critical section!
+               */
 
               sigdeliver(tcb);
             }

arch/arm/src/armv7-m/up_sigdeliver.c

@@ -110,9 +110,28 @@ void up_sigdeliver(void)
   sigdeliver           = (sig_deliver_t)rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
+#ifdef CONFIG_SMP
+  /* In the SMP case, up_schedule_sigaction(0) will have incremented
+   * 'irqcount' in order to force us into a critical section.  At a minimum,
+   * we must call leave_critical_section() at least once in order to
+   * compensate for that.
+   */
+
+#ifdef CONFIG_ARMV7M_USEBASEPRI
+  leave_critical_section((uint8_t)regs[REG_BASEPRI]);
+#else
+  leave_critical_section((uint16_t)regs[REG_PRIMASK]);
+#endif
+#endif /* CONFIG_SMP */
+
 #ifndef CONFIG_SUPPRESS_INTERRUPTS
   /* Then make sure that interrupts are enabled.  Signal handlers must always
    * run with interrupts enabled.
+   *
+   * REVISIT: 'irqcount' could still be greater than zero in the SMP case.
+   * This would be an issue if the signal handler were to suspend because
+   * the critical section would be re-established when the signal handler
+   * resumes.
    */
 
   up_irq_enable();

arch/xtensa/src/common/xtensa_schedsigaction.c

@@ -119,7 +119,9 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
 
           if (!CURRENT_REGS)
             {
-              /* In this case just deliver the signal now. */
+              /* In this case just deliver the signal now.
+               * REVISIT:  Signal handler will run in a critical section!
+               */
 
               sigdeliver(tcb);
             }
@@ -235,7 +237,9 @@ void up_schedule_sigaction(struct tcb_s *tcb, sig_deliver_t sigdeliver)
 
           if (cpu == me && !CURRENT_REGS)
             {
-              /* In this case just deliver the signal now. */
+              /* In this case just deliver the signal now.
+               * REVISIT:  Signal handler will run in a critical section!
+               */
 
               sigdeliver(tcb);
             }

arch/xtensa/src/common/xtensa_sigdeliver.c

@@ -100,9 +100,24 @@ void xtensa_sig_deliver(void)
   sigdeliver           = rtcb->xcp.sigdeliver;
   rtcb->xcp.sigdeliver = NULL;
 
+#ifdef CONFIG_SMP
+  /* In the SMP case, up_schedule_sigaction(0) will have incremented
+   * 'irqcount' in order to force us into a critical section.  At a minimum,
+   * we must call leave_critical_section() at least once in order to
+   * compensate for that.
+   */
+
+  leave_critical_section((regs[REG_PS]));
+#endif /* CONFIG_SMP */
+
 #ifndef CONFIG_SUPPRESS_INTERRUPTS
   /* Then make sure that interrupts are enabled.  Signal handlers must always
    * run with interrupts enabled.
+   *
+   * REVISIT: 'irqcount' could still be greater than zero in the SMP case.
+   * This would be an issue if the signal handler were to suspend because
+   * the critical section would be re-established when the signal handler
+   * resumes.
    */
 
   up_irq_enable();

include/nuttx/sched.h

@@ -615,7 +615,7 @@ struct tcb_s
   uint16_t flags;                        /* Misc. general status flags          */
   int16_t  lockcount;                    /* 0=preemptable (not-locked)          */
 #ifdef CONFIG_SMP
-  int16_t  irqcount;                     /* 0=interrupts enabled                */
+  int16_t  irqcount;                     /* 0=Not in critical section           */
 #endif
 #ifdef CONFIG_CANCELLATION_POINTS
   int16_t  cpcount;                      /* Nested cancellation point count     */