Review some SMP logic; update comments; refresh configuration.

configs/sim/README.txt

@@ -243,9 +243,6 @@ SMP
 
   You can enable SMP for ostest configuration by enabling:
 
-    -# CONFIG_EXPERIMENTAL is not set
-    +CONFIG_EXPERIMENTAL=y
-
     +CONFIG_SPINLOCK=y
     +CONFIG_SMP=y
     +CONFIG_SMP_NCPUS=2

configs/sim/ostest/defconfig

@@ -58,10 +58,13 @@ CONFIG_DEBUG_NOOPT=y
 # CONFIG_ARCH_AVR is not set
 # CONFIG_ARCH_HC is not set
 # CONFIG_ARCH_MIPS is not set
+# CONFIG_ARCH_MISOC is not set
 # CONFIG_ARCH_RGMP is not set
 # CONFIG_ARCH_RENESAS is not set
+# CONFIG_ARCH_RISCV is not set
 CONFIG_ARCH_SIM=y
 # CONFIG_ARCH_X86 is not set
+# CONFIG_ARCH_XTENSA is not set
 # CONFIG_ARCH_Z16 is not set
 # CONFIG_ARCH_Z80 is not set
 CONFIG_ARCH="sim"
@@ -79,6 +82,7 @@ CONFIG_SIM_NET_HOST_ROUTE=y
 # CONFIG_SIM_NET_BRIDGE is not set
 # CONFIG_SIM_FRAMEBUFFER is not set
 # CONFIG_SIM_SPIFLASH is not set
+# CONFIG_SIM_QSPIFLASH is not set
 
 #
 # Architecture Options
@@ -168,6 +172,7 @@ CONFIG_ARCH_HAVE_TICKLESS=y
 CONFIG_USEC_PER_TICK=10000
 # CONFIG_SYSTEM_TIME64 is not set
 # CONFIG_CLOCK_MONOTONIC is not set
+# CONFIG_ARCH_HAVE_TIMEKEEPING is not set
 # CONFIG_JULIAN_TIME is not set
 CONFIG_START_YEAR=2007
 CONFIG_START_MONTH=2
@@ -180,6 +185,7 @@ CONFIG_PREALLOC_TIMERS=8
 #
 # Tasks and Scheduling
 #
+# CONFIG_SMP is not set
 # CONFIG_INIT_NONE is not set
 CONFIG_INIT_ENTRYPOINT=y
 # CONFIG_INIT_FILEPATH is not set
@@ -262,6 +268,7 @@ CONFIG_PTHREAD_STACK_DEFAULT=8192
 CONFIG_DISABLE_POLL=y
 CONFIG_DEV_NULL=y
 # CONFIG_DEV_ZERO is not set
+# CONFIG_DEV_URANDOM is not set
 # CONFIG_DEV_LOOP is not set
 
 #
@@ -277,12 +284,16 @@ CONFIG_DEV_NULL=y
 # CONFIG_ARCH_HAVE_I2CRESET is not set
 # CONFIG_I2C is not set
 # CONFIG_SPI is not set
+# CONFIG_ARCH_HAVE_SPI_CRCGENERATION is not set
+# CONFIG_ARCH_HAVE_SPI_CS_CONTROL is not set
+# CONFIG_ARCH_HAVE_SPI_BITORDER is not set
 # CONFIG_I2S is not set
 
 #
 # Timer Driver Support
 #
 # CONFIG_TIMER is not set
+# CONFIG_ONESHOT is not set
 # CONFIG_RTC is not set
 # CONFIG_WATCHDOG is not set
 # CONFIG_ANALOG is not set
@@ -351,10 +362,12 @@ CONFIG_SERIAL_CONSOLE=y
 # CONFIG_SERIAL_OFLOWCONTROL is not set
 # CONFIG_SERIAL_DMA is not set
 # CONFIG_ARCH_HAVE_SERIAL_TERMIOS is not set
+# CONFIG_PSEUDOTERM is not set
 # CONFIG_USBDEV is not set
 # CONFIG_USBHOST is not set
 # CONFIG_HAVE_USBTRACE is not set
 # CONFIG_DRIVERS_WIRELESS is not set
+# CONFIG_DRIVERS_CONTACTLESS is not set
 
 #
 # System Logging
@@ -456,6 +469,8 @@ CONFIG_LIB_HOMEDIR="/"
 # CONFIG_LIBC_FLOATINGPOINT is not set
 CONFIG_LIBC_LONG_LONG=y
 # CONFIG_LIBC_IOCTL_VARIADIC is not set
+# CONFIG_LIBC_WCHAR is not set
+# CONFIG_LIBC_LOCALE is not set
 CONFIG_LIB_RAND_ORDER=1
 # CONFIG_EOL_IS_CR is not set
 # CONFIG_EOL_IS_LF is not set
@@ -501,9 +516,9 @@ CONFIG_ARCH_HAVE_TLS=y
 #
 # Examples
 #
+# CONFIG_EXAMPLES_CCTYPE is not set
 # CONFIG_EXAMPLES_CHAT is not set
 # CONFIG_EXAMPLES_CONFIGDATA is not set
-# CONFIG_EXAMPLES_CPUHOG is not set
 # CONFIG_EXAMPLES_DHCPD is not set
 # CONFIG_EXAMPLES_ELF is not set
 # CONFIG_EXAMPLES_FTPC is not set
@@ -535,10 +550,9 @@ CONFIG_EXAMPLES_OSTEST_RR_RANGE=10000
 CONFIG_EXAMPLES_OSTEST_RR_RUNS=10
 CONFIG_EXAMPLES_OSTEST_WAITRESULT=y
 # CONFIG_EXAMPLES_PCA9635 is not set
-# CONFIG_EXAMPLES_PIPE is not set
-# CONFIG_EXAMPLES_POLL is not set
 # CONFIG_EXAMPLES_POSIXSPAWN is not set
 # CONFIG_EXAMPLES_PPPD is not set
+# CONFIG_EXAMPLES_RFID_READUID is not set
 # CONFIG_EXAMPLES_RGBLED is not set
 # CONFIG_EXAMPLES_RGMP is not set
 # CONFIG_EXAMPLES_SENDMAIL is not set
@@ -577,6 +591,7 @@ CONFIG_EXAMPLES_OSTEST_WAITRESULT=y
 #
 # CONFIG_INTERPRETERS_FICL is not set
 # CONFIG_INTERPRETERS_MICROPYTHON is not set
+# CONFIG_INTERPRETERS_MINIBASIC is not set
 # CONFIG_INTERPRETERS_PCODE is not set
 
 #
@@ -620,6 +635,7 @@ CONFIG_EXAMPLES_OSTEST_WAITRESULT=y
 # CONFIG_READLINE_HAVE_EXTMATCH is not set
 # CONFIG_SYSTEM_READLINE is not set
 # CONFIG_SYSTEM_SUDOKU is not set
+# CONFIG_SYSTEM_TEE is not set
 # CONFIG_SYSTEM_UBLOXMODEM is not set
 # CONFIG_SYSTEM_VI is not set
 # CONFIG_SYSTEM_ZMODEM is not set

sched/irq/irq_csection.c

@@ -214,34 +214,38 @@ void leave_critical_section(irqstate_t flags)
 
   if (g_os_initstate >= OSINIT_TASKLISTS)
     {
-      /* If called from an interrupt handler, then just take the spinlock.
-       * If we are already in a critical section, this will lock the CPU
-       * in the interrupt handler.  Sounds worse than it is.
+      /* If called from an interrupt handler, then just release the
+       * spinlock.  The interrupt handling logic should already hold the
+       * spinlock if enter_critical_section() has been called.  Unlocking
+       * the spinlock will allow interrupt handlers on other CPUs to execute
+       * again.
        */
 
       if (up_interrupt_context())
         {
-          /* We are in an interrupt handler but within a critical section.
-           * Wait until we can get the spinlock (meaning that we are no
-           * longer in the critical section).
-           */
+          /* We are in an interrupt handler. Release the spinlock. */
 
           DEBUGASSERT(g_cpu_irqlock == SP_LOCKED);
-          spin_unlock(&g_cpu_irqlock);
+          if (g_cpu_irqset == 0)
+            {
+              spin_unlock(&g_cpu_irqlock);
+            }
         }
       else
         {
           FAR struct tcb_s *rtcb = this_task();
           DEBUGASSERT(rtcb != 0 && rtcb->irqcount > 0);
 
-          /* Normal tasking context */
-          /* Will we still have interrupts disabled after decrementing the
+          /* Normal tasking context.  We need to coordinate with other
+           * tasks.
+           *
+           * Will we still have interrupts disabled after decrementing the
            * count?
-          */
+           */
 
           if (rtcb->irqcount > 1)
             {
-              /* Yes... make sure that the spinlock is set */
+              /* Yes... the spinlock should remain set */
 
               DEBUGASSERT(g_cpu_irqlock == SP_LOCKED);
               rtcb->irqcount--;