Fix a deadlock when using the NSH ifconfig command over Telnet

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@4487 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 178 insertions, 0 deletions

diff --git a/nuttx/net/netdev_sem.c b/nuttx/net/netdev_sem.c
new file mode 100644
index 000000000..ba6299c62
--- /dev/null
+++ b/nuttx/net/netdev_sem.c
@@ -0,0 +1,178 @@
+/****************************************************************************
+ * net/netdev_sem.c
+ *
+ *   Copyright (C) 2012 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>
+
+#if defined(CONFIG_NET) && CONFIG_NSOCKET_DESCRIPTORS > 0
+
+#include <sys/types.h>
+
+#include <unistd.h>
+#include <semaphore.h>
+#include <assert.h>
+#include <errno.h>
+
+#include "net_internal.h"
+
+/****************************************************************************
+ * Definitions
+ ****************************************************************************/
+
+#define NO_HOLDER (pid_t)-1
+
+/****************************************************************************
+ * Priviate Types
+ ****************************************************************************/
+
+/* There is at least on context in which recursive semaphores are required:
+ * When netdev_foreach is used with a telnet client, we will deadlock if we
+ * do not provide this capability.
+ */
+
+struct netdev_sem_s
+{
+  sem_t        sem;
+  pid_t        holder;
+  unsigned int count;
+};
+
+/****************************************************************************
+ * Private Data
+ ****************************************************************************/
+
+/****************************************************************************
+ * Public Data
+ ****************************************************************************/
+
+static struct netdev_sem_s g_devlock;
+
+/****************************************************************************
+ * Private Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Global Functions
+ ****************************************************************************/
+
+/****************************************************************************
+ * Function: netdev_seminit
+ *
+ * Description:
+ *   Initialize the network device semaphore.
+ *
+ ****************************************************************************/
+
+void netdev_seminit(void)
+{
+  sem_init(&g_devlock.sem, 0, 1);
+  g_devlock.holder = NO_HOLDER;
+  g_devlock.count  = 0;
+}
+
+/****************************************************************************
+ * Function: netdev_semtake
+ *
+ * Description:
+ *   Get exclusive access to the network device list.
+ *
+ ****************************************************************************/
+
+void netdev_semtake(void)
+{
+  pid_t me = getpid();
+
+  /* Does this thread already hold the semaphore? */
+
+  if (g_devlock.holder == me)
+    {
+      /* Yes.. just increment the reference count */
+
+      g_devlock.count++;
+    }
+  else
+    {
+      /* No.. take the semaphore (perhaps waiting) */
+
+      while (uip_lockedwait(&g_devlock.sem) != 0)
+        {
+          /* The only case that an error should occur here is if
+           * the wait was awakened by a signal.
+           */
+
+          ASSERT(errno == EINTR);
+        }
+
+      /* Now this thread holds the semaphore */
+
+      g_devlock.holder = me;
+      g_devlock.count  = 1;
+    }
+}
+
+/****************************************************************************
+ * Function: netdev_semtake
+ *
+ * Description:
+ *   Release exclusive access to the network device list
+ *
+ ****************************************************************************/
+
+void netdev_semgive(void)
+{
+  DEBUGASSERT(g_devlock.holder == getpid() && g_devlock.count > 0);
+
+  /* If the count would go to zero, then release the semaphore */
+
+  if (g_devlock.count == 1)
+    {
+      /* We no longer hold the semaphore */
+
+      g_devlock.holder = NO_HOLDER;
+      g_devlock.count  = 0;
+      sem_post(&g_devlock.sem);
+    }
+  else
+    {
+      /* We still hold the semaphore. Just decrement the count */
+
+      g_devlock.count--;
+    }
+}
+
+#endif /* CONFIG_NET && CONFIG_NSOCKET_DESCRIPTORS */