posix: Simplify message queues

The mq_open() function returns a descriptor to a POSIX message queue
object identified by a name.  This is similar to sem_open().  In
contrast to the POSIX semaphore the POSIX message queues use a separate
object for the descriptor.  This extra object is superfluous, since the
object identifier can be used directly for this purpose, just like for
the semaphores.

Update #2702.
Update #2555.

1 files changed, 72 insertions, 132 deletions

diff --git a/cpukit/posix/src/mqueueopen.c b/cpukit/posix/src/mqueueopen.c
index 973c9b8e74..fe63d4ea6e 100644
--- a/cpukit/posix/src/mqueueopen.c
+++ b/cpukit/posix/src/mqueueopen.c
@@ -30,59 +30,48 @@
 #include "config.h"
 #endif
 
-#include <stdarg.h>
+#include <rtems/posix/mqueueimpl.h>
+#include <rtems/score/wkspace.h>
 
-#include <pthread.h>
-#include <limits.h>
-#include <errno.h>
+#include <stdarg.h>
 #include <fcntl.h>
-#include <mqueue.h>
-
-#include <rtems/score/todimpl.h>
-#include <rtems/score/watchdog.h>
-#include <rtems/posix/mqueueimpl.h>
-#include <rtems/seterr.h>
 
 #define MQ_OPEN_FAILED ((mqd_t) -1)
 
-static int _POSIX_Message_queue_Create_support(
-  const char                    *name_arg,
-  size_t                         name_len,
-  struct mq_attr                *attr_ptr,
-  POSIX_Message_queue_Control  **message_queue
+/*
+ *  There is no real basis for the default values.  They will work
+ *  but were not compared against any existing implementation for
+ *  compatibility.  See README.mqueue for an example program we
+ *  think will print out the defaults.  Report anything you find with it.
+ */
+static const struct mq_attr _POSIX_Message_queue_Default_attributes = {
+  .mq_maxmsg = 10,
+  .mq_msgsize = 16
+};
+
+static mqd_t _POSIX_Message_queue_Create(
+  const char           *name_arg,
+  size_t                name_len,
+  int                   oflag,
+  const struct mq_attr *attr
 )
 {
-  POSIX_Message_queue_Control   *the_mq;
-  struct mq_attr                 attr;
-  char                          *name;
+  POSIX_Message_queue_Control  *the_mq;
+  char                         *name;
 
   /* length of name has already been validated */
 
-  /*
-   *  There is no real basis for the default values.  They will work
-   *  but were not compared against any existing implementation for
-   *  compatibility.  See README.mqueue for an example program we
-   *  think will print out the defaults.  Report anything you find with it.
-   */
-  if ( attr_ptr == NULL ) {
-    attr.mq_maxmsg  = 10;
-    attr.mq_msgsize = 16;
-  } else {
-    if ( attr_ptr->mq_maxmsg <= 0 ){
-      rtems_set_errno_and_return_minus_one( EINVAL );
-    }
-
-    if ( attr_ptr->mq_msgsize <= 0 ){
-      rtems_set_errno_and_return_minus_one( EINVAL );
-    }
+  if ( attr->mq_maxmsg <= 0 ){
+    rtems_set_errno_and_return_value( EINVAL, MQ_OPEN_FAILED );
+  }
 
-    attr = *attr_ptr;
+  if ( attr->mq_msgsize <= 0 ){
+    rtems_set_errno_and_return_value( EINVAL, MQ_OPEN_FAILED );
   }
 
-  the_mq = _POSIX_Message_queue_Allocate();
+  the_mq = _POSIX_Message_queue_Allocate_unprotected();
   if ( !the_mq ) {
-    _Objects_Allocator_unlock();
-    rtems_set_errno_and_return_minus_one( ENFILE );
+    rtems_set_errno_and_return_value( ENFILE, MQ_OPEN_FAILED );
   }
 
   /*
@@ -92,12 +81,12 @@ static int _POSIX_Message_queue_Create_support(
   name = _Workspace_String_duplicate( name_arg, name_len );
   if ( !name ) {
     _POSIX_Message_queue_Free( the_mq );
-    _Objects_Allocator_unlock();
-    rtems_set_errno_and_return_minus_one( ENOMEM );
+    rtems_set_errno_and_return_value( ENOMEM, MQ_OPEN_FAILED );
   }
 
   the_mq->open_count = 1;
   the_mq->linked = true;
+  the_mq->oflag = oflag;
 
   /*
    *  NOTE: That thread blocking discipline should be based on the
@@ -106,17 +95,17 @@ static int _POSIX_Message_queue_Create_support(
    *  Joel: Cite POSIX or OpenGroup on above statement so we can determine
    *        if it is a real requirement.
    */
-  if ( !_CORE_message_queue_Initialize(
-           &the_mq->Message_queue,
-           CORE_MESSAGE_QUEUE_DISCIPLINES_FIFO,
-           attr.mq_maxmsg,
-           attr.mq_msgsize
-      ) ) {
-
+  if (
+    !_CORE_message_queue_Initialize(
+      &the_mq->Message_queue,
+      CORE_MESSAGE_QUEUE_DISCIPLINES_FIFO,
+      attr->mq_maxmsg,
+      attr->mq_msgsize
+    )
+  ) {
     _POSIX_Message_queue_Free( the_mq );
-    _Workspace_Free(name);
-    _Objects_Allocator_unlock();
-    rtems_set_errno_and_return_minus_one( ENOSPC );
+    _Workspace_Free( name );
+    rtems_set_errno_and_return_value( ENOSPC, MQ_OPEN_FAILED );
   }
 
   _Objects_Open_string(
@@ -124,11 +113,7 @@ static int _POSIX_Message_queue_Create_support(
     &the_mq->Object,
     name
   );
-
-  *message_queue = the_mq;
-
-  _Objects_Allocator_unlock();
-  return 0;
+  return the_mq->Object.id;
 }
 
 /*
@@ -142,36 +127,12 @@ mqd_t mq_open(
   /* struct mq_attr  attr */
 )
 {
-  /*
-   * mode is set but never used. GCC gives a warning for this
-   * and we need to tell GCC not to complain. But we have to
-   * have it because we have to work through the variable
-   * arguments to get to attr.
-   */
-  mode_t                          mode RTEMS_UNUSED;
-
-  va_list                         arg;
-  struct mq_attr                 *attr = NULL;
-  int                             status;
-  POSIX_Message_queue_Control    *the_mq;
-  POSIX_Message_queue_Control_fd *the_mq_fd;
-  size_t                          name_len;
-  Objects_Get_by_name_error       error;
-
-  if ( oflag & O_CREAT ) {
-    va_start(arg, oflag);
-    mode = va_arg( arg, mode_t );
-    attr = va_arg( arg, struct mq_attr * );
-    va_end(arg);
-  }
-
-  the_mq_fd = _POSIX_Message_queue_Allocate_fd();
-  if ( !the_mq_fd ) {
-    _Objects_Allocator_unlock();
-    rtems_set_errno_and_return_value( ENFILE, MQ_OPEN_FAILED );
-  }
-  the_mq_fd->oflag = oflag;
+  POSIX_Message_queue_Control *the_mq;
+  size_t                       name_len;
+  Objects_Get_by_name_error    error;
+  mqd_t                        status;
 
+  _Objects_Allocator_lock();
   the_mq = _POSIX_Message_queue_Get_by_name( name, &name_len, &error );
 
   /*
@@ -181,12 +142,15 @@ mqd_t mq_open(
    *  or some other miscellaneous error on the name.
    */
   if ( the_mq == NULL ) {
+    va_list               ap;
+    const struct mq_attr *attr;
+
     /*
      * Unless provided a valid name that did not already exist
      * and we are willing to create then it is an error.
      */
-    if ( !( error == OBJECTS_GET_BY_NAME_NO_OBJECT && (oflag & O_CREAT) ) ) {
-      _POSIX_Message_queue_Free_fd( the_mq_fd );
+
+    if ( error != OBJECTS_GET_BY_NAME_NO_OBJECT || ( oflag & O_CREAT ) == 0 ) {
       _Objects_Allocator_unlock();
       rtems_set_errno_and_return_value(
         _POSIX_Get_by_name_error( error ),
@@ -194,60 +158,36 @@ mqd_t mq_open(
       );
     }
 
-  } else {                /* name -> ID translation succeeded */
+    va_start( ap, oflag );
+    va_arg( ap, mode_t );
+    attr = va_arg( ap, const struct mq_attr * );
+    va_end( ap );
+
+    if ( attr == NULL ) {
+      attr = &_POSIX_Message_queue_Default_attributes;
+    }
+
+    /*
+     *  At this point, the message queue does not exist and everything has been
+     *  checked. We should go ahead and create a message queue.
+     */
+
+    status = _POSIX_Message_queue_Create( name, name_len, oflag, attr );
+  } else {
+
     /*
      * Check for existence with creation.
      */
-    if ( (oflag & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL) ) {
-      _POSIX_Message_queue_Free_fd( the_mq_fd );
+
+    if ( ( oflag & ( O_CREAT | O_EXCL ) ) == ( O_CREAT | O_EXCL ) ) {
       _Objects_Allocator_unlock();
       rtems_set_errno_and_return_value( EEXIST, MQ_OPEN_FAILED );
     }
 
-    /*
-     * In this case we need to do an ID->pointer conversion to
-     * check the mode.
-     */
     the_mq->open_count += 1;
-    the_mq_fd->Queue = the_mq;
-    _Objects_Open_string(
-      &_POSIX_Message_queue_Information_fds,
-      &the_mq_fd->Object,
-      NULL
-    );
-    _Objects_Allocator_unlock();
-    return the_mq_fd->Object.id;
-
+    status = the_mq->Object.id;
   }
 
-  /*
-   *  At this point, the message queue does not exist and everything has been
-   *  checked. We should go ahead and create a message queue.
-   */
-  status = _POSIX_Message_queue_Create_support(
-    name,
-    name_len,
-    attr,
-    &the_mq
-  );
-
-  /*
-   * errno was set by Create_support, so don't set it again.
-   */
-  if ( status != 0 ) {
-    _POSIX_Message_queue_Free_fd( the_mq_fd );
-    _Objects_Allocator_unlock();
-    return MQ_OPEN_FAILED;
-  }
-
-  the_mq_fd->Queue = the_mq;
-  _Objects_Open_string(
-    &_POSIX_Message_queue_Information_fds,
-    &the_mq_fd->Object,
-    NULL
-  );
-
   _Objects_Allocator_unlock();
-
-  return the_mq_fd->Object.id;
+  return status;
 }