NET: Fix some errors in recent network I/O buffering when stack runs from interrupt level

include/nuttx/net/net.h

@@ -156,7 +156,7 @@ int net_checksd(int fd, int oflags);
  * under sched/
  */
 
-void weak_function net_initialize(void);
+void net_initialize(void);
 void net_initlist(FAR struct socketlist *list);
 void net_releaselist(FAR struct socketlist *list);
 

net/iob/iob_alloc.c

@@ -107,8 +107,7 @@ static FAR struct iob_s *iob_tryalloc(bool throttled)
 #if CONFIG_IOB_THROTTLE > 0
   /* If there are free I/O buffers for this allocation */
 
-  DEBUGVERIFY(sem_getvalue(sem, &semcount));
-  if (semcount > 0)
+  if (sem->semcount > 0)
 #endif
     {
       /* Take the I/O buffer from the head of the free list */
@@ -122,9 +121,18 @@ static FAR struct iob_s *iob_tryalloc(bool throttled)
            */
 
           g_iob_freelist = iob->io_flink;
-          DEBUGVERIFY(sem_trywait(&g_iob_sem));
+
+          /* Take a semaphore count.  Note that we cannot do this in
+           * in the orthodox way by calling sem_wait() or sem_trywait()
+           * because this function may be called from an interrupt
+           * handler. Fortunately we know at at least one free buffer
+           * so a simple decrement is all that is needed.
+           */
+
+          g_iob_sem.semcount--;
+          DEBUGASSERT(g_iob_sem.semcount >= 0);
+
 #if CONFIG_IOB_THROTTLE > 0
-          //DEBUGVERIFY(sem_trywait(&g_throttle_sem));
           g_throttle_sem.semcount--;
           DEBUGASSERT(g_throttle_sem.semcount >= -CONFIG_IOB_THROTTLE);
 #endif

sched/os_start.c

@@ -448,12 +448,7 @@ void os_start(void)
   /* Initialize the network system */
 
 #ifdef CONFIG_NET
-#if 0
-  if (net_initialize != NULL)
-#endif
-    {
-      net_initialize();
-    }
+  net_initialize();
 #endif
 
   /* The processor specific details of running the operating system

sched/sem_trywait.c

@@ -116,8 +116,8 @@ int sem_trywait(FAR sem_t *sem)
 
       saved_state = irqsave();
 
-      /* Any further errors could only be occurred because the semaphore
-       * is not available.
+      /* Any further errors could only occurr because the semaphore is not
+       * available.
        */
 
       set_errno(EAGAIN);