From d017e3eb2eb95d5122d1596084883b2a82b76d89 Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Sat, 13 Feb 2016 10:25:36 -0600
Subject: [PATCH] SMP: Forgot to add a file before the last commit

---
 sched/irq/irq_csection.c | 142 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 142 insertions(+)
 create mode 100644 sched/irq/irq_csection.c

diff --git a/sched/irq/irq_csection.c b/sched/irq/irq_csection.c
new file mode 100644
index 0000000000..536117151d
--- /dev/null
+++ b/sched/irq/irq_csection.c
@@ -0,0 +1,142 @@
+/****************************************************************************
+ * sched/irq/irq_csection.c
+ *
+ *   Copyright (C) 2007-2008, 2010 Gregory Nutt. All rights reserved.
+ *   Author: Gregory Nutt <gnutt@nuttx.org>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ * 3. Neither the name NuttX nor the names of its contributors may be
+ *    used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *
+ ****************************************************************************/
+
+/****************************************************************************
+ * Included Files
+ ****************************************************************************/
+
+#include <nuttx/config.h>
+
+#include <nuttx/spinlock.h>
+#include <arch/irq.h>
+
+#include "sched/sched.h"
+#include "irq/irq.h"
+
+#ifdef CONFIG_SMP
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+/* This is the spinlock that enforces critical sections when interrupts are
+ * disabled.
+ */
+
+spinlock_t g_cpu_irqlock = SP_UNLOCKED;
+
+/****************************************************************************
+ * Public Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Name: enter_critical_section
+ *
+ * Description:
+ *   Take the CPU IRQ lock and disable interrupts on all CPUs.  A thread-
+ *   specific counter is increment to indicate that the thread has IRQs
+ *   disabled and to support nested calls to enter_critical_section().
+ *
+ ****************************************************************************/
+
+irqstate_t enter_critical_section(void)
+{
+  FAR struct tcb_s *rtcb = this_task();
+
+  /* Do we already have interrupts disabled? */
+
+  if (rtcb->irqcount > 0)
+    {
+      /* Yes... make sure that the spinlock is set and increment the IRQ
+       * lock count.
+       */
+
+      DEBUGASSERT(g_cpu_irqlock == SP_LOCKED && rtcb->irqcount < INT16_MAX);
+      rtcb->irqcount++;
+    }
+  else
+    {
+      /* NO.. Take the spinlock to get exclusive access and set the lock
+       * count to 1.
+       */
+
+      spin_lock(&g_cpu_irqlock);
+      rtcb->irqcount = 1;
+    }
+
+  /* Then disable interrupts (if they have not already been disabeld) */
+
+  return irqsave();
+}
+
+/****************************************************************************
+ * Name: leave_critical_section
+ *
+ * Description:
+ *   Decrement the IRQ lock count and if it decrements to zero then release
+ *   the spinlock.
+ *
+ ****************************************************************************/
+
+void leave_critical_section(irqstate_t flags)
+{
+  FAR struct tcb_s *rtcb = this_task();
+
+  DEBUGASSERT(rtcb->irqcount > 0);
+
+  /* Will we still have interrupts disabled after decrementing the count? */
+
+  if (rtcb->irqcount > 1)
+    {
+      /* Yes... make sure that the spinlock is set */
+
+      DEBUGASSERT(g_cpu_irqlock == SP_LOCKED);
+      rtcb->irqcount--;
+    }
+  else
+    {
+      /* NO.. Take the spinlock to get exclusive access. */
+
+      rtcb->irqcount = 0;
+      spin_unlock(g_cpu_irqlock);
+    }
+
+  /* Restore the previous interrupt state which may still be interrupts
+   * disabled (but we don't have a mechanism to verify that now)
+   */
+
+  irqrestore(flags);
+}
+
+#endif /* CONFIG_SMP */