drivers: Disable priority inheritance on all semaphores used for signaling

drivers/net/slip.c

@@ -55,8 +55,9 @@
 #include <debug.h>
 
 #include <nuttx/irq.h>
-#include <nuttx/net/net.h>
 #include <nuttx/clock.h>
+#include <nuttx/semaphore.h>
+#include <nuttx/net/net.h>
 #include <nuttx/net/netdev.h>
 #include <nuttx/net/ip.h>
 #include <nuttx/net/slip.h>
@@ -965,6 +966,7 @@ int slip_initialize(int intf, FAR const char *devname)
   /* Initialize the wait semaphore */
 
   sem_init(&priv->waitsem, 0, 0);
+  sem_setprotocol(&priv->waitsem, SEM_PRIO_NONE);
 
   /* Put the interface in the down state.  This usually amounts to resetting
    * the device and/or calling slip_ifdown().

drivers/net/tun.c

@@ -884,11 +884,17 @@ static int tun_dev_init(FAR struct tun_device_s *priv, FAR struct file *filep,
 #endif
   priv->dev.d_private = (FAR void *)priv; /* Used to recover private state from dev */
 
-  /* Initialize the wait semaphore */
+  /* Initialize the mutual exlcusion and wait semaphore */
 
   sem_init(&priv->waitsem, 0, 1);
   sem_init(&priv->read_wait_sem, 0, 0);
 
+  /* The wait semaphore is used for signaling and, hence, should not have
+   * priority inheritance enabled.
+   */
+
+  sem_setprotocol(&priv->read_wait_sem, SEM_PRIO_NONE);
+
   /* Create a watchdog for timing polling for and timing of transmisstions */
 
   priv->txpoll        = wd_create();  /* Create periodic poll timer */