drivers/serial/serial.c open, read, write, and poll methods will not return a short transfer or an EINTR error if a signal is received while waiting (only)

git-svn-id: https://nuttx.svn.sourceforge.net/svnroot/nuttx/trunk@5022 7fd9a85b-ad96-42d3-883c-3090e2eb8679

17 files changed, 338 insertions, 115 deletions

diff --git a/nuttx/ChangeLog b/nuttx/ChangeLog
index 364de21a3d..78a6323dde 100644
--- a/nuttx/ChangeLog
+++ b/nuttx/ChangeLog
@@ -3154,3 +3154,7 @@
 	* arch/arm/src/stm32/stm32f2xx_dma.c and stm32f4xx_dma.c: Backed out the
 	  DMA priority change just above.  The reduced SD card frequency was
 	  necessary and sufficient to resolve the problem.
+	* drivers/serial/serial.c:  open, read, write, and poll methods may now
+	  abort return EINTR (or a short transfer size) if a signal is received
+	  while waiting to receive or send serial data.  This behavior is required
+	  by POSIX.
diff --git a/nuttx/TODO b/nuttx/TODO
index f9fc558eab..543d15f707 100644
--- a/nuttx/TODO
+++ b/nuttx/TODO
@@ -1,4 +1,4 @@
-NuttX TODO List (Last updated August 7, 2012)
+NuttX TODO List (Last updated August 12, 2012)
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 This file summarizes known NuttX bugs, limitations, inconsistencies with 
@@ -16,7 +16,7 @@ nuttx/
  (17)  Network (net/, drivers/net)
   (3)  USB (drivers/usbdev, drivers/usbhost)
  (11)  Libraries (lib/)
- (10)  File system/Generic drivers (fs/, drivers/)
+  (9)  File system/Generic drivers (fs/, drivers/)
   (5)  Graphics subystem (graphics/)
   (1)  Pascal add-on (pcode/)
   (1)  Documentation (Documentation/)
@@ -750,21 +750,6 @@ o File system / Generic drivers (fs/, drivers/)
   Status:      Open
   Priority:    Low
 
-  Title:       SERIAL DRIVER DOES NOT RETURN WHEN SIGNAL RECEIVED
-  Description: The serial driver (drivers/serial) should return with an
-               error and errno=EINTR when an interrupt is received.  However,
-               the serial driver just continues waiting:
-
-               static void uart_takesem(FAR sem_t *sem)
-               {
-                 while (sem_wait(sem) != 0)
-                   {
-                     ASSERT(*get_errno_ptr() == EINTR);
-                   }
-               }
-  Status:      Open
-  Priority     Medium
-
   Title:       POLLHUP SUPPORT
   Description: All drivers that support the poll method should also report
                POLLHUP event when the driver is closedd.
diff --git a/nuttx/drivers/serial/serial.c b/nuttx/drivers/serial/serial.c
index e0bd6dc0b9..c0ebd245a0 100644
--- a/nuttx/drivers/serial/serial.c
+++ b/nuttx/drivers/serial/serial.c
@@ -112,16 +112,29 @@ static const struct file_operations g_serialops =
  * Name: uart_takesem
  ************************************************************************************/
 
-static void uart_takesem(FAR sem_t *sem)
+static int uart_takesem(FAR sem_t *sem, bool errout)
 {
-  while (sem_wait(sem) != 0)
+  /* Loop, ignoring interrupts, until we have successfully acquired the semaphore */
+
+  while (sem_wait(sem) != OK)
     {
-      /* The only case that an error should occur here is if
-       * the wait was awakened by a signal.
+      /* The only case that an error should occur here is if the wait was awakened
+       * by a signal.
        */
 
       ASSERT(get_errno() == EINTR);
+
+      /* When the signal is received, should we errout? Or should we just continue
+       * waiting until we have the semaphore?
+       */
+
+      if (errout)
+        {
+          return -EINTR;
+        }
     }
+
+  return OK;
 }
 
 /************************************************************************************
@@ -161,10 +174,11 @@ static void uart_pollnotify(FAR uart_dev_t *dev, pollevent_t eventset)
  * Name: uart_putxmitchar
  ************************************************************************************/
 
-static void uart_putxmitchar(FAR uart_dev_t *dev, int ch)
+static int uart_putxmitchar(FAR uart_dev_t *dev, int ch)
 {
   irqstate_t flags;
   int nexthead;
+  int ret;
 
   /* Increment to see what the next head pointer will be.  We need to use the "next"
    * head pointer to determine when the circular buffer would overrun
@@ -184,29 +198,43 @@ static void uart_putxmitchar(FAR uart_dev_t *dev, int ch)
         {
           dev->xmit.buffer[dev->xmit.head] = ch;
           dev->xmit.head = nexthead;
-          return;
+          return OK;
         }
       else
         {
-          /* Inform the interrupt level logic that we are waiting.
-           * This and the following steps must be atomic.
+          /* Inform the interrupt level logic that we are waiting. This and
+           * the following steps must be atomic.
            */
 
           flags = irqsave();
           dev->xmitwaiting = true;
 
-          /* Wait for some characters to be sent from the buffer
-           * with the TX interrupt enabled.  When the TX interrupt
-           * is enabled, uart_xmitchars should execute and remove
-           * some of the data from the TX buffer.
+          /* Wait for some characters to be sent from the buffer with the TX
+           * interrupt enabled.  When the TX interrupt is enabled, uart_xmitchars
+           * should execute and remove some of the data from the TX buffer.
            */
 
           uart_enabletxint(dev);
-          uart_takesem(&dev->xmitsem);
+          ret = uart_takesem(&dev->xmitsem, true);
           uart_disabletxint(dev);
           irqrestore(flags);
+
+          /* Check if we were awakened by signal. */
+
+          if (ret < 0)
+            {
+             /* A signal received while waiting for the xmit buffer to become
+              * non-full will abort the transfer.
+              */
+
+              return -EINTR;
+            }
         }
     }
+
+  /* We won't get here */
+
+  return OK;
 }
 
 /************************************************************************************
@@ -241,9 +269,10 @@ static ssize_t uart_irqwrite(FAR uart_dev_t *dev, FAR const char *buffer, size_t
 
 static ssize_t uart_write(FAR struct file *filep, FAR const char *buffer, size_t buflen)
 {
-  FAR struct inode *inode = filep->f_inode;
-  FAR uart_dev_t   *dev   = inode->i_private;
-  ssize_t           ret   = buflen;
+  FAR struct inode *inode  = filep->f_inode;
+  FAR uart_dev_t   *dev    = inode->i_private;
+  ssize_t           nread  = buflen;
+  int               ret;
 
   /* We may receive console writes through this path from
    * interrupt handlers and from debug output in the IDLE task!
@@ -266,9 +295,18 @@ static ssize_t uart_write(FAR struct file *filep, FAR const char *buffer, size_t
         }
     }
 
-  /* Only one user can be accessing dev->xmit.head at once */
+  /* Only one user can access dev->xmit.head at a time */
 
-  uart_takesem(&dev->xmit.sem);
+  ret = (ssize_t)uart_takesem(&dev->xmit.sem, true);
+  if (ret < 0)
+    {
+      /* A signal received while waiting for access to the xmit.head will
+       * abort the transfer.  After the transfer has started, we are committed
+       * and signals will be ignored.
+       */
+
+      return ret;
+    }
 
   /* Loop while we still have data to copy to the transmit buffer.
    * we add data to the head of the buffer; uart_xmitchars takes the
@@ -280,15 +318,50 @@ static ssize_t uart_write(FAR struct file *filep, FAR const char *buffer, size_t
     {
       int ch = *buffer++;
 
+      /* If this is the console, then we should replace LF with CR-LF */
+
+      ret = OK;
+      if (dev->isconsole && ch == '\n')
+        {
+          ret = uart_putxmitchar(dev, '\r');
+        }
+
       /* Put the character into the transmit buffer */
 
-      uart_putxmitchar(dev, ch);
+      if (ret == OK)
+        {
+          ret = uart_putxmitchar(dev, ch);
+        }
 
-      /* If this is the console, then we should replace LF with LF-CR */
+      /* Were we awakened by a signal?  That should be the only condition that
+       * uart_putxmitchar() should return an error.
+       */
 
-      if (dev->isconsole && ch == '\n')
+      if (ret < 0)
         {
-          uart_putxmitchar(dev, '\r');
+          /* POSIX requires that we return -1 and errno set if no data was
+           * transferred.  Otherwise, we return the number of bytes in the
+           * interrupted transfer.
+           */
+
+          if (buflen < nread)
+            {
+              /* Some data was transferred.  Return the number of bytes that were
+               * successfully transferred.
+               */
+
+              nread -= buflen;
+            }
+          else
+            {
+              /* No data was transferred. Return -EINTR.  The VFS layer will
+               * set the errno value appropriately).
+               */
+ 
+              nread = -EINTR;
+            }
+
+          break;
         }
     }
 
@@ -298,7 +371,7 @@ static ssize_t uart_write(FAR struct file *filep, FAR const char *buffer, size_t
     }
 
   uart_givesem(&dev->xmit.sem);
-  return ret;
+  return nread;
 }
 
 /************************************************************************************
@@ -312,10 +385,20 @@ static ssize_t uart_read(FAR struct file *filep, FAR char *buffer, size_t buflen
   irqstate_t        flags;
   ssize_t           recvd = 0;
   int16_t           tail;
+  int               ret;
 
-  /* Only one user can be accessing dev->recv.tail at once */
+  /* Only one user can access dev->recv.tail at a time */
 
-  uart_takesem(&dev->recv.sem);
+  ret = uart_takesem(&dev->recv.sem, true);
+  if (ret < 0)
+    {
+      /* A signal received while waiting for access to the recv.tail will avort
+       * the transfer.  After the transfer has started, we are committed and
+       * signals will be ignored.
+       */
+
+      return ret;
+    }
 
   /* Loop while we still have data to copy to the receive buffer.
    * we add data to the head of the buffer; uart_xmitchars takes the
@@ -352,6 +435,7 @@ static ssize_t uart_read(FAR struct file *filep, FAR char *buffer, size_t buflen
             {
               tail = 0;
             }
+
           dev->recv.tail = tail;
         }
 
@@ -426,12 +510,34 @@ static ssize_t uart_read(FAR struct file *filep, FAR char *buffer, size_t buflen
               uart_enablerxint(dev);
 
               /* Now wait with the Rx interrupt re-enabled.  NuttX will
-               * automatically re-enable global interrupts when this
-               * thread goes to sleep.
+               * automatically re-enable global interrupts when this thread
+               * goes to sleep.
                */
 
-              uart_takesem(&dev->recvsem);
+              ret = uart_takesem(&dev->recvsem, true);
               irqrestore(flags);
+
+              /* Was a signal received while waiting for data to be received? */
+
+              if (ret < 0)
+                {
+                  /* POSIX requires that we return after a signal is received.
+                   * If some bytes were read, we need to return the number of bytes
+                   * read; if no bytes were read, we need to return -1 with the
+                   * errno set correctly.
+                   */
+
+                  if (recvd == 0)
+                    {
+                      /* No bytes were read, return -EINTR (the VFS layer will
+                       * set the errno value appropriately.
+                       */
+
+                      recvd = -EINTR;
+                    }
+
+                  break;
+                }
             }
           else
             {
@@ -472,7 +578,7 @@ int uart_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup)
   FAR uart_dev_t   *dev   = inode->i_private;
   pollevent_t       eventset;
   int               ndx;
-  int               ret   = OK;
+  int               ret;
   int               i;
 
   /* Some sanity checking */
@@ -486,7 +592,16 @@ int uart_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup)
 
   /* Are we setting up the poll?  Or tearing it down? */
 
-  uart_takesem(&dev->pollsem);
+  ret = uart_takesem(&dev->pollsem, true);
+  if (ret < 0)
+    {
+      /* A signal received while waiting for access to the poll data
+       * will abort the operation.
+       */
+
+      return ret;
+    }
+
   if (setup)
     {
       /* This is a request to set up the poll.  Find an available
@@ -514,31 +629,43 @@ int uart_poll(FAR struct file *filep, FAR struct pollfd *fds, bool setup)
           goto errout;
         }
 
-      /* Should immediately notify on any of the requested events?
+      /* Should we immediately notify on any of the requested events?
        * First, check if the xmit buffer is full.
+       *
+       * Get exclusive access to the xmit buffer indices.  NOTE: that we do not
+       * let this wait be interrupted by a signal (we probably should, but that
+       * would be a little awkward).
        */
 
       eventset = 0;
+      (void)uart_takesem(&dev->xmit.sem, false);
 
-      uart_takesem(&dev->xmit.sem);
       ndx = dev->xmit.head + 1;
       if (ndx >= dev->xmit.size)
         {
           ndx = 0;
         }
+
       if (ndx != dev->xmit.tail)
        {
          eventset |= POLLOUT;
        }
+
       uart_givesem(&dev->xmit.sem);
 
-      /* Check if the receive buffer is empty */
+      /* Check if the receive buffer is empty
+       *
+       * Get exclusive access to the recv buffer indices.  NOTE: that we do not
+       * let this wait be interrupted by a signal (we probably should, but that
+       * would be a little awkward).
+       */
 
-      uart_takesem(&dev->recv.sem);
+      (void)uart_takesem(&dev->recv.sem, false);
       if (dev->recv.head != dev->recv.tail)
        {
          eventset |= POLLIN;
        }
+
       uart_givesem(&dev->recv.sem);
 
       if (eventset)
@@ -588,7 +715,13 @@ static int uart_close(FAR struct file *filep)
   FAR uart_dev_t   *dev   = inode->i_private;
   irqstate_t        flags;
 
-  uart_takesem(&dev->closesem);
+  /* Get exclusive access to the close semaphore (to synchronize open/close operations.
+   * NOTE: that we do not let this wait be interrupted by a signal.  Technically, we
+   * should, but almost no one every checks the return value from close() so we avoid
+   * a potential memory leak by ignoring signals in this case.
+   */
+
+  (void)uart_takesem(&dev->closesem, false);
   if (dev->open_count > 1)
     {
       dev->open_count--;
@@ -653,11 +786,19 @@ static int uart_open(FAR struct file *filep)
   struct inode *inode = filep->f_inode;
   uart_dev_t   *dev   = inode->i_private;
   uint8_t       tmp;
-  int           ret   = OK;
+  int           ret;
 
-  /* If the port is the middle of closing, wait until the close is finished */
+  /* If the port is the middle of closing, wait until the close is finished.
+   * If a signal is received while we are waiting, then return EINTR.
+   */
+
+  ret = uart_takesem(&dev->closesem, true);
+  if (ret < 0)
+    {
+      /* A signal received while waiting for the last close operation. */
 
-  uart_takesem(&dev->closesem);
+      return ret;
+    }
 
   /* Start up serial port */
   /* Increment the count of references to the device. */
diff --git a/nuttx/include/netinet/arp.h b/nuttx/include/netinet/arp.h
index 34cfc84a4c..e318945aa7 100644
--- a/nuttx/include/netinet/arp.h
+++ b/nuttx/include/netinet/arp.h
@@ -58,14 +58,17 @@
 #define SIOCDARP        _ARPIOC(2) /* Delete an ARP mapping */
 #define SIOCGARP        _ARPIOC(3) /* Get an ARP mapping */
 
-/* Values for the FLAGS field in struct arpreq */
-
-#define ATF_COM         0x01       /* Lookup complete */
-#define ATF_PERM        0x02       /* Permanent entry */
-#define ATF_PUBL        0x04       /* Publish entry */
-#define ATF_USETRAILERS 0x10       /* Trailers requested */
-#define ATF_NETMASK     0x20       /* Use a netmask */
-#define ATF_DONTPUB     0x40       /* Don't answer */
+/* Definitions for bits in field arp_flags of struct arpreq.  If the
+ * ATF_NETMASK flag is set, then arp_netmask should be valid.  This should
+ * be set to 0xffffffff, or 0 to remove an existing arp entry.
+ */
+
+#define ATF_COM         (1 << 0)   /* Lookup complete */
+#define ATF_PERM        (1 << 1)   /* Permanent entry */
+#define ATF_PUBL        (1 << 2)   /* Publish entry */
+#define ATF_USETRAILERS (1 << 3)   /* Trailers requested (obsolete) */
+#define ATF_NETMASK     (1 << 4)   /* Use a netmask */
+#define ATF_DONTPUB     (1 << 5)   /* Don't answer */
 
 /****************************************************************************
  * Public Type Definitions
diff --git a/nuttx/include/nuttx/net/ioctl.h b/nuttx/include/nuttx/net/ioctl.h
index 5bce5eaf1c..be3f597f47 100644
--- a/nuttx/include/nuttx/net/ioctl.h
+++ b/nuttx/include/nuttx/net/ioctl.h
@@ -149,6 +149,7 @@
 /****************************************************************************
  * Type Definitions
  ****************************************************************************/
+/* See include/net/if.h */
 
 /****************************************************************************
  * Public Function Prototypes
diff --git a/nuttx/lib/stdio/lib_libfwrite.c b/nuttx/lib/stdio/lib_libfwrite.c
index e2c35e3e99..e71866b498 100644
--- a/nuttx/lib/stdio/lib_libfwrite.c
+++ b/nuttx/lib/stdio/lib_libfwrite.c
@@ -2,7 +2,7 @@
  * lib/stdio/lib_libfwrite.c
  *
  *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *   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
diff --git a/nuttx/lib/stdio/lib_lowinstream.c b/nuttx/lib/stdio/lib_lowinstream.c
index 6dcc4a37e6..c97a4721fd 100644
--- a/nuttx/lib/stdio/lib_lowinstream.c
+++ b/nuttx/lib/stdio/lib_lowinstream.c
@@ -1,8 +1,8 @@
 /****************************************************************************
  * lib/stdio/lib_lowinstream.c
  *
- *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *   Copyright (C) 2007-2009, 2011-2012 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
@@ -42,7 +42,9 @@
 #ifdef CONFIG_ARCH_LOWGETC
 
 #include <stdio.h>
+#include <assert.h>
 #include <errno.h>
+
 #include <nuttx/arch.h>
 
 #include "lib_internal.h"
@@ -57,10 +59,19 @@
 
 static int lowinstream_getc(FAR struct lib_instream_s *this)
 {
-  if (this && up_getc(ch) != EOF)
+  int ret;
+
+  DEBUGASSERT(this);
+
+  /* Get the next character from the incoming stream */
+
+  ret = up_getc(ch)
+  if (ret != EOF)
     {
       this->nget++;
     }
+
+  return ret;
 }
 
 /****************************************************************************
diff --git a/nuttx/lib/stdio/lib_lowoutstream.c b/nuttx/lib/stdio/lib_lowoutstream.c
index 726bd84d7d..092f39ca25 100644
--- a/nuttx/lib/stdio/lib_lowoutstream.c
+++ b/nuttx/lib/stdio/lib_lowoutstream.c
@@ -42,6 +42,7 @@
 #ifdef CONFIG_ARCH_LOWPUTC
 
 #include <stdio.h>
+#include <assert.h>
 #include <errno.h>
 #include <nuttx/arch.h>
 
@@ -57,7 +58,9 @@
 
 static void lowoutstream_putc(FAR struct lib_outstream_s *this, int ch)
 {
-  if (this && up_putc(ch) != EOF)
+  DEBUGASSERT(this);
+
+  if (up_putc(ch) != EOF)
     {
       this->nput++;
     }
diff --git a/nuttx/lib/stdio/lib_meminstream.c b/nuttx/lib/stdio/lib_meminstream.c
index 839e562199..a842096fb4 100644
--- a/nuttx/lib/stdio/lib_meminstream.c
+++ b/nuttx/lib/stdio/lib_meminstream.c
@@ -1,8 +1,8 @@
 /****************************************************************************
  * lib/stdio/lib_meminstream.c
  *
- *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *   Copyright (C) 2007-2009, 2011-2012 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
@@ -37,6 +37,8 @@
  * Included Files
  ****************************************************************************/
 
+#include <assert.h>
+
 #include "lib_internal.h"
 
 /****************************************************************************
@@ -52,7 +54,11 @@ static int meminstream_getc(FAR struct lib_instream_s *this)
   FAR struct lib_meminstream_s *mthis = (FAR struct lib_meminstream_s *)this;
   int ret;
 
-  if (this && this->nget < mthis->buflen)
+  DEBUGASSERT(this);
+
+  /* Get the next character (if any) from the buffer */
+
+  if (this->nget < mthis->buflen)
     {
       ret = mthis->buffer[this->nget];
       this->nget++;
@@ -61,6 +67,7 @@ static int meminstream_getc(FAR struct lib_instream_s *this)
     {
       ret = EOF;
     }
+
   return ret;
 }
 
diff --git a/nuttx/lib/stdio/lib_memoutstream.c b/nuttx/lib/stdio/lib_memoutstream.c
index 007ab89763..21197358b7 100644
--- a/nuttx/lib/stdio/lib_memoutstream.c
+++ b/nuttx/lib/stdio/lib_memoutstream.c
@@ -37,6 +37,8 @@
  * Included Files
  ****************************************************************************/
 
+#include <assert.h>
+
 #include "lib_internal.h"
 
 /****************************************************************************
@@ -51,12 +53,14 @@ static void memoutstream_putc(FAR struct lib_outstream_s *this, int ch)
 {
   FAR struct lib_memoutstream_s *mthis = (FAR struct lib_memoutstream_s *)this;
 
+  DEBUGASSERT(this);
+
   /* If this will not overrun the buffer, then write the character to the
    * buffer.  Not that buflen was pre-decremented when the stream was
    * created so it is okay to write past the end of the buflen by one.
    */
 
-  if (this && this->nput < mthis->buflen)
+  if (this->nput < mthis->buflen)
     {
       mthis->buffer[this->nput] = ch;
       this->nput++;
diff --git a/nuttx/lib/stdio/lib_nullinstream.c b/nuttx/lib/stdio/lib_nullinstream.c
index 271cba396f..0eadb0a8e4 100644
--- a/nuttx/lib/stdio/lib_nullinstream.c
+++ b/nuttx/lib/stdio/lib_nullinstream.c
@@ -1,8 +1,8 @@
 /****************************************************************************
  * lib/stdio/lib_nullinstream.c
  *
- *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *   Copyright (C) 2007-2009, 2011-2012 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
@@ -39,6 +39,7 @@
 
 #include <stdio.h>
 #include <errno.h>
+
 #include "lib_internal.h"
 
 /****************************************************************************
diff --git a/nuttx/lib/stdio/lib_nulloutstream.c b/nuttx/lib/stdio/lib_nulloutstream.c
index 520df459ea..69878fd579 100644
--- a/nuttx/lib/stdio/lib_nulloutstream.c
+++ b/nuttx/lib/stdio/lib_nulloutstream.c
@@ -38,7 +38,9 @@
  ****************************************************************************/
 
 #include <stdio.h>
+#include <assert.h>
 #include <errno.h>
+
 #include "lib_internal.h"
 
 /****************************************************************************
@@ -47,6 +49,7 @@
 
 static void nulloutstream_putc(FAR struct lib_outstream_s *this, int ch)
 {
+  DEBUGASSERT(this);
   this->nput++;
 }
 
diff --git a/nuttx/lib/stdio/lib_rawinstream.c b/nuttx/lib/stdio/lib_rawinstream.c
index ead3116b4f..aacc8f8678 100644
--- a/nuttx/lib/stdio/lib_rawinstream.c
+++ b/nuttx/lib/stdio/lib_rawinstream.c
@@ -1,8 +1,8 @@
 /****************************************************************************
  * lib/stdio/lib_rawinstream.c
  *
- *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *   Copyright (C) 2007-2009, 2011-2012 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
@@ -38,7 +38,9 @@
  ****************************************************************************/
 
 #include <unistd.h>
+#include <assert.h>
 #include <errno.h>
+
 #include "lib_internal.h"
 
 /****************************************************************************
@@ -52,23 +54,27 @@
 static int rawinstream_getc(FAR struct lib_instream_s *this)
 {
   FAR struct lib_rawinstream_s *rthis = (FAR struct lib_rawinstream_s *)this;
+  int nwritten;
   char ch;
 
-  if (this && rthis->fd >= 0)
+  DEBUGASSERT(this && rthis->fd >= 0);
+
+  /* Attempt to read one character */
+
+  nwritten = read(rthis->fd, &ch, 1);
+  if (nwritten == 1)
     {
-      int nwritten;
-      do
-        {
-          nwritten = read(rthis->fd, &ch, 1);
-          if (nwritten == 1)
-            {
-              this->nget++;
-              return ch;
-            }
-        }
-      while (nwritten < 0 && get_errno() == EINTR);
+      this->nget++;
+      return ch;
     }
 
+  /* Return EOF on any failure to read from the incoming byte stream. The
+   * only expected error is EINTER meaning that the read was interrupted
+   * by a signal.  A Zero return value would indicated an end-of-file
+   * confition.
+   */
+
+  DEBUGASSERT(nwritten == 0 || get_errno() == EINTR);
   return EOF;
 }
 
diff --git a/nuttx/lib/stdio/lib_rawoutstream.c b/nuttx/lib/stdio/lib_rawoutstream.c
index ce9d33280e..b4a20958b3 100644
--- a/nuttx/lib/stdio/lib_rawoutstream.c
+++ b/nuttx/lib/stdio/lib_rawoutstream.c
@@ -38,7 +38,9 @@
  ****************************************************************************/
 
 #include <unistd.h>
+#include <assert.h>
 #include <errno.h>
+
 #include "lib_internal.h"
 
 /****************************************************************************
@@ -52,19 +54,28 @@
 static void rawoutstream_putc(FAR struct lib_outstream_s *this, int ch)
 {
   FAR struct lib_rawoutstream_s *rthis = (FAR struct lib_rawoutstream_s *)this;
+  int nwritten;
   char buffer = ch;
-  if (this && rthis->fd >= 0)
+
+  DEBUGASSERT(this && rthis->fd >= 0);
+
+  /* Loop until the character is successfully transferred  */
+
+  for (;;)
     {
-      int nwritten;
-      do
+      nwritten = write(rthis->fd, &buffer, 1);
+      if (nwritten == 1)
         {
-          nwritten = write(rthis->fd, &buffer, 1);
-          if (nwritten == 1)
-            {
-              this->nput++;
-            }
+          this->nput++;
+          return;
         }
-      while (nwritten < 0 && get_errno() == EINTR);
+
+      /* The only expected error is EINTR, meaning that the write operation
+       * was awakened by a signal.  Zero would not be a valid return value
+       * either.
+       */
+
+      DEBUGASSERT(nwritten < 0 && get_errno() == EINTR);
     }
 }
 
diff --git a/nuttx/lib/stdio/lib_stdinstream.c b/nuttx/lib/stdio/lib_stdinstream.c
index d89b6b63a0..77aab9ec88 100644
--- a/nuttx/lib/stdio/lib_stdinstream.c
+++ b/nuttx/lib/stdio/lib_stdinstream.c
@@ -1,8 +1,8 @@
 /****************************************************************************
  * lib/stdio/lib_stdinstream.c
  *
- *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *   Copyright (C) 2007-2009, 2011-2012 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
@@ -37,6 +37,8 @@
  * Included Files
  ****************************************************************************/
 
+#include <assert.h>
+
 #include "lib_internal.h"
 
 /****************************************************************************
@@ -50,16 +52,19 @@
 static int stdinstream_getc(FAR struct lib_instream_s *this)
 {
   FAR struct lib_stdinstream_s *sthis = (FAR struct lib_stdinstream_s *)this;
-  if (this)
+  int ret;
+
+  DEBUGASSERT(this);
+
+  /* Get the next character from the incoming stream */
+
+  ret = getc(sthis->stream);
+  if (ret != EOF)
     {
-      int ret = getc(sthis->stream);
-      if (ret != EOF)
-        {
-          this->nget++;
-        }
-      return ret;
+      this->nget++;
     }
-  return EOF;
+ 
+ return ret;
 }
 
 /****************************************************************************
diff --git a/nuttx/lib/stdio/lib_stdoutstream.c b/nuttx/lib/stdio/lib_stdoutstream.c
index 12e78ce53f..b8dd0bf63a 100644
--- a/nuttx/lib/stdio/lib_stdoutstream.c
+++ b/nuttx/lib/stdio/lib_stdoutstream.c
@@ -1,8 +1,8 @@
 /****************************************************************************
  * lib/stdio/lib_stdoutstream.c
  *
- *   Copyright (C) 2007-2009, 2011 Gregory Nutt. All rights reserved.
- *   Author: Gregory Nutt <spudmonkey@racsa.co.cr>
+ *   Copyright (C) 2007-2009, 2011-2012 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
@@ -38,6 +38,8 @@
  ****************************************************************************/
 
 #include <fcntl.h>
+#include <assert.h>
+#include <errno.h>
 
 #include "lib_internal.h"
 
@@ -52,12 +54,26 @@
 static void stdoutstream_putc(FAR struct lib_outstream_s *this, int ch)
 {
   FAR struct lib_stdoutstream_s *sthis = (FAR struct lib_stdoutstream_s *)this;
-  if (this)
+  int result;
+
+  DEBUGASSERT(this && sthis->stream);
+
+  /* Loop until the character is successfully transferred  */
+
+  for (;;)
     {
-      if (putc(ch, sthis->stream) != EOF)
+      result = fputc(ch, sthis->stream);
+      if (result != EOF)
         {
           this->nput++;
+          return;
         }
+
+      /* EINTR (meaning that fputc was interrupted by a signal) is the only
+       * expected error.
+       */
+
+      DEBUGASSERT(get_errno() == EINTR);
     }
 }
 
diff --git a/nuttx/lib/stdio/lib_syslogstream.c b/nuttx/lib/stdio/lib_syslogstream.c
index 20c6165ca9..1a47f6abbe 100644
--- a/nuttx/lib/stdio/lib_syslogstream.c
+++ b/nuttx/lib/stdio/lib_syslogstream.c
@@ -40,6 +40,7 @@
 #include <nuttx/config.h>
 
 #include <unistd.h>
+#include <assert.h>
 #include <errno.h>
 
 #include <nuttx/syslog.h>
@@ -62,10 +63,31 @@
 
 static void syslogstream_putc(FAR struct lib_outstream_s *this, int ch)
 {
-  /* Write the character to the supported logging device */
-
-  (void)syslog_putc(ch);
-  this->nput++;
+  int ret;
+
+  /* Try writing until the write was successful or until an irrecoverable
+   * error occurs.
+   */
+
+  for (;;)
+    {
+      /* Write the character to the supported logging device */
+
+      ret = syslog_putc(ch);
+      if (ret == OK)
+        {
+          this->nput++;
+          return;
+        }
+
+      /* On failure syslog_putc will return a negated errno value.  The
+       * errno variable will not be set.  The special value -EINTR means that
+       * syslog_putc() was awakened by a signal.  This is not a real error and
+       * must be ignored in this context.
+       */
+
+      DEBUGASSERT(ret == -EINTR);
+    }
 }
 
 /****************************************************************************