[ae68ff0] | 1 | @c |
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[6449498] | 2 | @c COPYRIGHT (c) 1988-2002. |
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[ae68ff0] | 3 | @c On-Line Applications Research Corporation (OAR). |
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| 4 | @c All rights reserved. |
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| 5 | @c |
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[139b2e4a] | 6 | @c $Id$ |
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| 7 | @c |
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[ae68ff0] | 8 | |
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| 9 | @chapter Message Manager |
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[20515fc] | 10 | |
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[169502e] | 11 | @cindex messages |
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| 12 | @cindex message queues |
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| 13 | |
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[ae68ff0] | 14 | @section Introduction |
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| 15 | |
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| 16 | The message manager provides communication and |
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| 17 | synchronization capabilities using RTEMS message queues. The |
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| 18 | directives provided by the message manager are: |
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| 19 | |
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| 20 | @itemize @bullet |
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[f331481c] | 21 | @item @code{@value{DIRPREFIX}message_queue_create} - Create a queue |
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| 22 | @item @code{@value{DIRPREFIX}message_queue_ident} - Get ID of a queue |
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| 23 | @item @code{@value{DIRPREFIX}message_queue_delete} - Delete a queue |
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| 24 | @item @code{@value{DIRPREFIX}message_queue_send} - Put message at rear of a queue |
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| 25 | @item @code{@value{DIRPREFIX}message_queue_urgent} - Put message at front of a queue |
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| 26 | @item @code{@value{DIRPREFIX}message_queue_broadcast} - Broadcast N messages to a queue |
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| 27 | @item @code{@value{DIRPREFIX}message_queue_receive} - Receive message from a queue |
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| 28 | @item @code{@value{DIRPREFIX}message_queue_get_number_pending} - Get number of messages pending on a queue |
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[75e22db] | 29 | @item @code{@value{DIRPREFIX}message_queue_flush} - Flush all messages on a queue |
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[ae68ff0] | 30 | @end itemize |
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| 31 | |
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| 32 | @section Background |
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[20515fc] | 33 | |
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[ae68ff0] | 34 | @subsection Messages |
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| 35 | |
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| 36 | A message is a variable length buffer where |
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| 37 | information can be stored to support communication. The length |
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| 38 | of the message and the information stored in that message are |
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| 39 | user-defined and can be actual data, pointer(s), or empty. |
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| 40 | |
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| 41 | @subsection Message Queues |
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| 42 | |
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| 43 | A message queue permits the passing of messages among |
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| 44 | tasks and ISRs. Message queues can contain a variable number of |
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| 45 | messages. Normally messages are sent to and received from the |
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[75e22db] | 46 | queue in FIFO order using the @code{@value{DIRPREFIX}message_queue_send} |
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| 47 | directive. However, the @code{@value{DIRPREFIX}message_queue_urgent} |
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| 48 | directive can be used to place |
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[ae68ff0] | 49 | messages at the head of a queue in LIFO order. |
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| 50 | |
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| 51 | Synchronization can be accomplished when a task can |
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| 52 | wait for a message to arrive at a queue. Also, a task may poll |
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| 53 | a queue for the arrival of a message. |
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| 54 | |
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| 55 | The maximum length message which can be sent is set |
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| 56 | on a per message queue basis. |
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| 57 | |
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[ed11cadf] | 58 | @subsection Building a Message Queue Attribute Set |
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[ae68ff0] | 59 | |
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[169502e] | 60 | @cindex message queue attributes |
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| 61 | |
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[ae68ff0] | 62 | In general, an attribute set is built by a bitwise OR |
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| 63 | of the desired attribute components. The set of valid message |
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| 64 | queue attributes is provided in the following table: |
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| 65 | |
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| 66 | @itemize @bullet |
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[f331481c] | 67 | @item @code{@value{RPREFIX}FIFO} - tasks wait by FIFO (default) |
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| 68 | @item @code{@value{RPREFIX}PRIORITY} - tasks wait by priority |
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| 69 | @item @code{@value{RPREFIX}LOCAL} - local message queue (default) |
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| 70 | @item @code{@value{RPREFIX}GLOBAL} - global message queue |
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[ae68ff0] | 71 | @end itemize |
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| 72 | |
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| 73 | |
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| 74 | An attribute listed as a default is not required to |
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| 75 | appear in the attribute list, although it is a good programming |
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| 76 | practice to specify default attributes. If all defaults are |
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[75e22db] | 77 | desired, the attribute @code{@value{RPREFIX}DEFAULT_ATTRIBUTES} |
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| 78 | should be specified on this call. |
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[ae68ff0] | 79 | |
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| 80 | This example demonstrates the attribute_set parameter |
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| 81 | needed to create a local message queue with the task priority |
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| 82 | waiting queue discipline. The attribute_set parameter to the |
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[75e22db] | 83 | @code{@value{DIRPREFIX}message_queue_create} directive could be either |
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[f331481c] | 84 | @code{@value{RPREFIX}PRIORITY} or |
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[a3a7527] | 85 | @code{@value{RPREFIX}LOCAL @value{OR} @value{RPREFIX}PRIORITY}. |
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[f331481c] | 86 | The attribute_set parameter can be set to @code{@value{RPREFIX}PRIORITY} |
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[75e22db] | 87 | because @code{@value{RPREFIX}LOCAL} is the default for all created |
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| 88 | message queues. If a similar message queue were to be known globally, then the |
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[a3a7527] | 89 | attribute_set parameter would be |
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| 90 | @code{@value{RPREFIX}GLOBAL @value{OR} @value{RPREFIX}PRIORITY}. |
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[ae68ff0] | 91 | |
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| 92 | @subsection Building a MESSAGE_QUEUE_RECEIVE Option Set |
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| 93 | |
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| 94 | In general, an option is built by a bitwise OR of the |
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| 95 | desired option components. The set of valid options for the |
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[75e22db] | 96 | @code{@value{DIRPREFIX}message_queue_receive} directive are |
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| 97 | listed in the following table: |
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[ae68ff0] | 98 | |
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| 99 | @itemize @bullet |
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[f331481c] | 100 | @item @code{@value{RPREFIX}WAIT} - task will wait for a message (default) |
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| 101 | @item @code{@value{RPREFIX}NO_WAIT} - task should not wait |
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[ae68ff0] | 102 | @end itemize |
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| 103 | |
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| 104 | An option listed as a default is not required to |
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| 105 | appear in the option OR list, although it is a good programming |
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| 106 | practice to specify default options. If all defaults are |
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[75e22db] | 107 | desired, the option @code{@value{RPREFIX}DEFAULT_OPTIONS} should |
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| 108 | be specified on this call. |
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[ae68ff0] | 109 | |
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| 110 | This example demonstrates the option parameter needed |
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| 111 | to poll for a message to arrive. The option parameter passed to |
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[75e22db] | 112 | the @code{@value{DIRPREFIX}message_queue_receive} directive should |
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| 113 | be @code{@value{RPREFIX}NO_WAIT}. |
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[ae68ff0] | 114 | |
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| 115 | @section Operations |
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[20515fc] | 116 | |
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[ae68ff0] | 117 | @subsection Creating a Message Queue |
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| 118 | |
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[75e22db] | 119 | The @code{@value{DIRPREFIX}message_queue_create} directive creates a message |
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[ae68ff0] | 120 | queue with the user-defined name. The user specifies the |
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| 121 | maximum message size and maximum number of messages which can be |
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| 122 | placed in the message queue at one time. The user may select |
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| 123 | FIFO or task priority as the method for placing waiting tasks in |
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| 124 | the task wait queue. RTEMS allocates a Queue Control Block |
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| 125 | (QCB) from the QCB free list to maintain the newly created queue |
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| 126 | as well as memory for the message buffer pool associated with |
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| 127 | this message queue. RTEMS also generates a message queue ID |
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| 128 | which is returned to the calling task. |
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| 129 | |
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| 130 | For GLOBAL message queues, the maximum message size |
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| 131 | is effectively limited to the longest message which the MPCI is |
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| 132 | capable of transmitting. |
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| 133 | |
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| 134 | @subsection Obtaining Message Queue IDs |
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| 135 | |
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| 136 | When a message queue is created, RTEMS generates a |
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| 137 | unique message queue ID. The message queue ID may be obtained |
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| 138 | by either of two methods. First, as the result of an invocation |
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[75e22db] | 139 | of the @code{@value{DIRPREFIX}message_queue_create} directive, the |
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| 140 | queue ID is stored in a user provided location. Second, the queue |
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| 141 | ID may be obtained later using the @code{@value{DIRPREFIX}message_queue_ident} |
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| 142 | directive. The queue ID is used by other message manager |
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| 143 | directives to access this message queue. |
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[ae68ff0] | 144 | |
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| 145 | @subsection Receiving a Message |
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| 146 | |
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[75e22db] | 147 | The @code{@value{DIRPREFIX}message_queue_receive} directive attempts to |
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[ae68ff0] | 148 | retrieve a message from the specified message queue. If at |
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| 149 | least one message is in the queue, then the message is removed |
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| 150 | from the queue, copied to the caller's message buffer, and |
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| 151 | returned immediately along with the length of the message. When |
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| 152 | messages are unavailable, one of the following situations |
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| 153 | applies: |
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| 154 | |
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| 155 | @itemize @bullet |
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| 156 | @item By default, the calling task will wait forever for the |
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| 157 | message to arrive. |
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| 158 | |
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[f331481c] | 159 | @item Specifying the @code{@value{RPREFIX}NO_WAIT} option forces an immediate return |
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[ae68ff0] | 160 | with an error status code. |
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| 161 | |
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| 162 | @item Specifying a timeout limits the period the task will |
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| 163 | wait before returning with an error status. |
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| 164 | @end itemize |
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| 165 | |
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| 166 | If the task waits for a message, then it is placed in |
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| 167 | the message queue's task wait queue in either FIFO or task |
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| 168 | priority order. All tasks waiting on a message queue are |
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| 169 | returned an error code when the message queue is deleted. |
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| 170 | |
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| 171 | @subsection Sending a Message |
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| 172 | |
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| 173 | Messages can be sent to a queue with the |
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[75e22db] | 174 | @code{@value{DIRPREFIX}message_queue_send} and |
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| 175 | @code{@value{DIRPREFIX}message_queue_urgent} directives. These |
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[ae68ff0] | 176 | directives work identically when tasks are waiting to receive a |
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| 177 | message. A task is removed from the task waiting queue, |
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| 178 | unblocked, and the message is copied to a waiting task's |
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| 179 | message buffer. |
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| 180 | |
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| 181 | When no tasks are waiting at the queue, |
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[75e22db] | 182 | @code{@value{DIRPREFIX}message_queue_send} places the |
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| 183 | message at the rear of the message queue, while |
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| 184 | @code{@value{DIRPREFIX}message_queue_urgent} places the message at the |
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[ae68ff0] | 185 | front of the queue. The message is copied to a message buffer |
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| 186 | from this message queue's buffer pool and then placed in the |
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| 187 | message queue. Neither directive can successfully send a |
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| 188 | message to a message queue which has a full queue of pending |
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| 189 | messages. |
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| 190 | |
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| 191 | @subsection Broadcasting a Message |
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| 192 | |
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[75e22db] | 193 | The @code{@value{DIRPREFIX}message_queue_broadcast} directive sends the same |
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[ae68ff0] | 194 | message to every task waiting on the specified message queue as |
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| 195 | an atomic operation. The message is copied to each waiting |
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| 196 | task's message buffer and each task is unblocked. The number of |
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| 197 | tasks which were unblocked is returned to the caller. |
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| 198 | |
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| 199 | @subsection Deleting a Message Queue |
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| 200 | |
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[75e22db] | 201 | The @code{@value{DIRPREFIX}message_queue_delete} directive removes a message |
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[ae68ff0] | 202 | queue from the system and frees its control block as well as the |
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| 203 | memory associated with this message queue's message buffer pool. |
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| 204 | A message queue can be deleted by any local task that knows the |
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| 205 | message queue's ID. As a result of this directive, all tasks |
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| 206 | blocked waiting to receive a message from the message queue will |
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| 207 | be readied and returned a status code which indicates that the |
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| 208 | message queue was deleted. Any subsequent references to the |
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| 209 | message queue's name and ID are invalid. Any messages waiting |
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| 210 | at the message queue are also deleted and deallocated. |
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| 211 | |
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| 212 | @section Directives |
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| 213 | |
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| 214 | This section details the message manager's |
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| 215 | directives. A subsection is dedicated to each of this manager's |
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| 216 | directives and describes the calling sequence, related |
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| 217 | constants, usage, and status codes. |
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| 218 | |
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[169502e] | 219 | @c |
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| 220 | @c |
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| 221 | @c |
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[ae68ff0] | 222 | @page |
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| 223 | @subsection MESSAGE_QUEUE_CREATE - Create a queue |
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| 224 | |
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[169502e] | 225 | @cindex create a message queue |
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| 226 | |
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[ae68ff0] | 227 | @subheading CALLING SEQUENCE: |
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| 228 | |
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[61389eac] | 229 | @ifset is-C |
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[169502e] | 230 | @findex rtems_message_queue_create |
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[ae68ff0] | 231 | @example |
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| 232 | rtems_status_code rtems_message_queue_create( |
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| 233 | rtems_name name, |
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[ef47c44f] | 234 | uint32_t count, |
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| 235 | uint32_t max_message_size, |
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[ae68ff0] | 236 | rtems_attribute attribute_set, |
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| 237 | rtems_id *id |
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| 238 | ); |
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| 239 | @end example |
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[61389eac] | 240 | @end ifset |
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| 241 | |
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| 242 | @ifset is-Ada |
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| 243 | @example |
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| 244 | procedure Message_Queue_Create ( |
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| 245 | Name : in RTEMS.Name; |
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| 246 | Count : in RTEMS.Unsigned32; |
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| 247 | Max_Message_Size : in RTEMS.Unsigned32; |
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| 248 | Attribute_Set : in RTEMS.Attribute; |
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| 249 | ID : out RTEMS.ID; |
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| 250 | Result : out RTEMS.Status_Codes |
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| 251 | ); |
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| 252 | @end example |
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| 253 | @end ifset |
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[ae68ff0] | 254 | |
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| 255 | @subheading DIRECTIVE STATUS CODES: |
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[f331481c] | 256 | @code{@value{RPREFIX}SUCCESSFUL} - queue created successfully@* |
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[a570a14] | 257 | @code{@value{RPREFIX}INVALID_NAME} - invalid queue name@* |
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[f8892c9] | 258 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{id} is NULL@* |
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[f331481c] | 259 | @code{@value{RPREFIX}INVALID_NUMBER} - invalid message count@* |
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| 260 | @code{@value{RPREFIX}INVALID_SIZE} - invalid message size@* |
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| 261 | @code{@value{RPREFIX}TOO_MANY} - too many queues created@* |
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[d3b7d98a] | 262 | @code{@value{RPREFIX}UNSATISFIED} - unable to allocate message buffers@* |
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[f331481c] | 263 | @code{@value{RPREFIX}MP_NOT_CONFIGURED} - multiprocessing not configured@* |
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| 264 | @code{@value{RPREFIX}TOO_MANY} - too many global objects |
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[ae68ff0] | 265 | |
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| 266 | @subheading DESCRIPTION: |
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| 267 | |
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| 268 | This directive creates a message queue which resides |
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| 269 | on the local node with the user-defined name specified in name. |
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| 270 | For control and maintenance of the queue, RTEMS allocates and |
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| 271 | initializes a QCB. Memory is allocated from the RTEMS Workspace |
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| 272 | for the specified count of messages, each of max_message_size |
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| 273 | bytes in length. The RTEMS-assigned queue id, returned in id, |
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| 274 | is used to access the message queue. |
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| 275 | |
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[f331481c] | 276 | Specifying @code{@value{RPREFIX}PRIORITY} in attribute_set causes tasks |
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[ae68ff0] | 277 | waiting for a message to be serviced according to task priority. |
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[d3b7d98a] | 278 | When @code{@value{RPREFIX}FIFO} is specified, waiting tasks are serviced |
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| 279 | in First In-First Out order. |
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[ae68ff0] | 280 | |
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| 281 | @subheading NOTES: |
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| 282 | |
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| 283 | This directive will not cause the calling task to be |
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| 284 | preempted. |
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| 285 | |
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| 286 | The following message queue attribute constants are |
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| 287 | defined by RTEMS: |
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| 288 | |
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| 289 | @itemize @bullet |
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[f331481c] | 290 | @item @code{@value{RPREFIX}FIFO} - tasks wait by FIFO (default) |
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| 291 | @item @code{@value{RPREFIX}PRIORITY} - tasks wait by priority |
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| 292 | @item @code{@value{RPREFIX}LOCAL} - local message queue (default) |
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| 293 | @item @code{@value{RPREFIX}GLOBAL} - global message queue |
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[ae68ff0] | 294 | @end itemize |
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| 295 | |
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| 296 | Message queues should not be made global unless |
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| 297 | remote tasks must interact with the created message queue. This |
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| 298 | is to avoid the system overhead incurred by the creation of a |
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| 299 | global message queue. When a global message queue is created, |
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| 300 | the message queue's name and id must be transmitted to every |
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| 301 | node in the system for insertion in the local copy of the global |
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| 302 | object table. |
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| 303 | |
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| 304 | For GLOBAL message queues, the maximum message size |
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| 305 | is effectively limited to the longest message which the MPCI is |
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| 306 | capable of transmitting. |
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| 307 | |
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| 308 | The total number of global objects, including message |
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| 309 | queues, is limited by the maximum_global_objects field in the |
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| 310 | configuration table. |
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| 311 | |
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[169502e] | 312 | @c |
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| 313 | @c |
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| 314 | @c |
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[ae68ff0] | 315 | @page |
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| 316 | @subsection MESSAGE_QUEUE_IDENT - Get ID of a queue |
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| 317 | |
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[169502e] | 318 | @cindex get ID of a message queue |
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| 319 | |
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[ae68ff0] | 320 | @subheading CALLING SEQUENCE: |
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| 321 | |
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[61389eac] | 322 | @ifset is-C |
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[169502e] | 323 | @findex rtems_message_queue_ident |
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[ae68ff0] | 324 | @example |
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| 325 | rtems_status_code rtems_message_queue_ident( |
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[ef47c44f] | 326 | rtems_name name, |
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| 327 | uint32_t node, |
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| 328 | rtems_id *id |
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[ae68ff0] | 329 | ); |
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| 330 | @end example |
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[61389eac] | 331 | @end ifset |
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| 332 | |
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| 333 | @ifset is-Ada |
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| 334 | @example |
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| 335 | procedure Message_Queue_Ident ( |
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| 336 | Name : in RTEMS.Name; |
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| 337 | Node : in RTEMS.Unsigned32; |
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| 338 | ID : out RTEMS.ID; |
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| 339 | Result : out RTEMS.Status_Codes |
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| 340 | ); |
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| 341 | @end example |
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| 342 | @end ifset |
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[ae68ff0] | 343 | |
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| 344 | @subheading DIRECTIVE STATUS CODES: |
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[f331481c] | 345 | @code{@value{RPREFIX}SUCCESSFUL} - queue identified successfully@* |
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[f8892c9] | 346 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{id} is NULL@* |
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[f331481c] | 347 | @code{@value{RPREFIX}INVALID_NAME} - queue name not found@* |
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| 348 | @code{@value{RPREFIX}INVALID_NODE} - invalid node id |
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[ae68ff0] | 349 | |
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| 350 | @subheading DESCRIPTION: |
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| 351 | |
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| 352 | This directive obtains the queue id associated with |
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| 353 | the queue name specified in name. If the queue name is not |
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| 354 | unique, then the queue id will match one of the queues with that |
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| 355 | name. However, this queue id is not guaranteed to correspond to |
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| 356 | the desired queue. The queue id is used with other message |
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| 357 | related directives to access the message queue. |
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| 358 | |
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| 359 | @subheading NOTES: |
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| 360 | |
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| 361 | This directive will not cause the running task to be |
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| 362 | preempted. |
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| 363 | |
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[f331481c] | 364 | If node is @code{@value{RPREFIX}SEARCH_ALL_NODES}, all nodes are searched |
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[ae68ff0] | 365 | with the local node being searched first. All other nodes are |
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| 366 | searched with the lowest numbered node searched first. |
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| 367 | |
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| 368 | If node is a valid node number which does not |
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| 369 | represent the local node, then only the message queues exported |
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| 370 | by the designated node are searched. |
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| 371 | |
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| 372 | This directive does not generate activity on remote |
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| 373 | nodes. It accesses only the local copy of the global object |
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| 374 | table. |
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| 375 | |
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[169502e] | 376 | @c |
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| 377 | @c |
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| 378 | @c |
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[ae68ff0] | 379 | @page |
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| 380 | @subsection MESSAGE_QUEUE_DELETE - Delete a queue |
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| 381 | |
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[169502e] | 382 | @cindex delete a message queue |
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| 383 | |
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[ae68ff0] | 384 | @subheading CALLING SEQUENCE: |
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| 385 | |
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[61389eac] | 386 | @ifset is-C |
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[169502e] | 387 | @findex rtems_message_queue_delete |
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[ae68ff0] | 388 | @example |
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| 389 | rtems_status_code rtems_message_queue_delete( |
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| 390 | rtems_id id |
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| 391 | ); |
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| 392 | @end example |
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[61389eac] | 393 | @end ifset |
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| 394 | |
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| 395 | @ifset is-Ada |
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| 396 | @example |
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| 397 | procedure Message_Queue_Delete ( |
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| 398 | ID : in RTEMS.ID; |
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| 399 | Result : out RTEMS.Status_Codes |
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| 400 | ); |
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| 401 | @end example |
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| 402 | @end ifset |
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[ae68ff0] | 403 | |
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| 404 | @subheading DIRECTIVE STATUS CODES: |
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[f331481c] | 405 | @code{@value{RPREFIX}SUCCESSFUL} - queue deleted successfully@* |
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| 406 | @code{@value{RPREFIX}INVALID_ID} - invalid queue id@* |
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| 407 | @code{@value{RPREFIX}ILLEGAL_ON_REMOTE_OBJECT} - cannot delete remote queue |
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[ae68ff0] | 408 | |
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| 409 | @subheading DESCRIPTION: |
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| 410 | |
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| 411 | This directive deletes the message queue specified by |
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| 412 | id. As a result of this directive, all tasks blocked waiting to |
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| 413 | receive a message from this queue will be readied and returned a |
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| 414 | status code which indicates that the message queue was deleted. |
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| 415 | If no tasks are waiting, but the queue contains messages, then |
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| 416 | RTEMS returns these message buffers back to the system message |
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| 417 | buffer pool. The QCB for this queue as well as the memory for |
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| 418 | the message buffers is reclaimed by RTEMS. |
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| 419 | |
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| 420 | @subheading NOTES: |
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| 421 | |
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| 422 | The calling task will be preempted if its preemption |
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| 423 | mode is enabled and one or more local tasks with a higher |
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| 424 | priority than the calling task are waiting on the deleted queue. |
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| 425 | The calling task will NOT be preempted if the tasks that are |
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| 426 | waiting are remote tasks. |
---|
| 427 | |
---|
| 428 | The calling task does not have to be the task that |
---|
| 429 | created the queue, although the task and queue must reside on |
---|
| 430 | the same node. |
---|
| 431 | |
---|
| 432 | When the queue is deleted, any messages in the queue |
---|
| 433 | are returned to the free message buffer pool. Any information |
---|
| 434 | stored in those messages is lost. |
---|
| 435 | |
---|
| 436 | When a global message queue is deleted, the message |
---|
| 437 | queue id must be transmitted to every node in the system for |
---|
| 438 | deletion from the local copy of the global object table. |
---|
| 439 | |
---|
| 440 | Proxies, used to represent remote tasks, are |
---|
| 441 | reclaimed when the message queue is deleted. |
---|
| 442 | |
---|
[169502e] | 443 | @c |
---|
| 444 | @c |
---|
| 445 | @c |
---|
[ae68ff0] | 446 | @page |
---|
| 447 | @subsection MESSAGE_QUEUE_SEND - Put message at rear of a queue |
---|
| 448 | |
---|
[169502e] | 449 | @cindex send message to a queue |
---|
| 450 | |
---|
[ae68ff0] | 451 | @subheading CALLING SEQUENCE: |
---|
| 452 | |
---|
[61389eac] | 453 | @ifset is-C |
---|
[169502e] | 454 | @findex rtems_message_queue_send |
---|
[ae68ff0] | 455 | @example |
---|
| 456 | rtems_status_code rtems_message_queue_send( |
---|
[ef47c44f] | 457 | rtems_id id, |
---|
| 458 | void *buffer, |
---|
| 459 | size_t size |
---|
[ae68ff0] | 460 | ); |
---|
| 461 | @end example |
---|
[61389eac] | 462 | @end ifset |
---|
| 463 | |
---|
| 464 | @ifset is-Ada |
---|
| 465 | @example |
---|
| 466 | procedure Message_Queue_Send ( |
---|
| 467 | ID : in RTEMS.ID; |
---|
| 468 | Buffer : in RTEMS.Address; |
---|
| 469 | Size : in RTEMS.Unsigned32; |
---|
| 470 | Result : out RTEMS.Status_Codes |
---|
| 471 | ); |
---|
| 472 | @end example |
---|
| 473 | @end ifset |
---|
[ae68ff0] | 474 | |
---|
| 475 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 476 | @code{@value{RPREFIX}SUCCESSFUL} - message sent successfully@* |
---|
| 477 | @code{@value{RPREFIX}INVALID_ID} - invalid queue id@* |
---|
| 478 | @code{@value{RPREFIX}INVALID_SIZE} - invalid message size@* |
---|
[f8892c9] | 479 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{buffer} is NULL@* |
---|
[f331481c] | 480 | @code{@value{RPREFIX}UNSATISFIED} - out of message buffers@* |
---|
| 481 | @code{@value{RPREFIX}TOO_MANY} - queue's limit has been reached |
---|
[ae68ff0] | 482 | |
---|
| 483 | @subheading DESCRIPTION: |
---|
| 484 | |
---|
| 485 | This directive sends the message buffer of size bytes |
---|
| 486 | in length to the queue specified by id. If a task is waiting at |
---|
| 487 | the queue, then the message is copied to the waiting task's |
---|
| 488 | buffer and the task is unblocked. If no tasks are waiting at the |
---|
| 489 | queue, then the message is copied to a message buffer which is |
---|
| 490 | obtained from this message queue's message buffer pool. The |
---|
| 491 | message buffer is then placed at the rear of the queue. |
---|
| 492 | |
---|
| 493 | @subheading NOTES: |
---|
| 494 | |
---|
| 495 | The calling task will be preempted if it has |
---|
| 496 | preemption enabled and a higher priority task is unblocked as |
---|
| 497 | the result of this directive. |
---|
| 498 | |
---|
| 499 | Sending a message to a global message queue which |
---|
| 500 | does not reside on the local node will generate a request to the |
---|
| 501 | remote node to post the message on the specified message queue. |
---|
| 502 | |
---|
| 503 | If the task to be unblocked resides on a different |
---|
| 504 | node from the message queue, then the message is forwarded to |
---|
| 505 | the appropriate node, the waiting task is unblocked, and the |
---|
| 506 | proxy used to represent the task is reclaimed. |
---|
| 507 | |
---|
[169502e] | 508 | @c |
---|
| 509 | @c |
---|
| 510 | @c |
---|
[ae68ff0] | 511 | @page |
---|
| 512 | @subsection MESSAGE_QUEUE_URGENT - Put message at front of a queue |
---|
| 513 | |
---|
[169502e] | 514 | @cindex put message at front of queue |
---|
| 515 | |
---|
[ae68ff0] | 516 | @subheading CALLING SEQUENCE: |
---|
| 517 | |
---|
[61389eac] | 518 | @ifset is-C |
---|
[169502e] | 519 | @findex rtems_message_queue_urgent |
---|
[ae68ff0] | 520 | @example |
---|
| 521 | rtems_status_code rtems_message_queue_urgent( |
---|
[ef47c44f] | 522 | rtems_id id, |
---|
| 523 | void *buffer, |
---|
| 524 | size_t size |
---|
[ae68ff0] | 525 | ); |
---|
| 526 | @end example |
---|
[61389eac] | 527 | @end ifset |
---|
| 528 | |
---|
| 529 | @ifset is-Ada |
---|
| 530 | @example |
---|
| 531 | procedure Message_Queue_Urgent ( |
---|
| 532 | ID : in RTEMS.ID; |
---|
| 533 | Buffer : in RTEMS.Address; |
---|
| 534 | Size : in RTEMS.Unsigned32; |
---|
| 535 | Result : out RTEMS.Status_Codes |
---|
| 536 | ); |
---|
| 537 | @end example |
---|
| 538 | @end ifset |
---|
[ae68ff0] | 539 | |
---|
| 540 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 541 | @code{@value{RPREFIX}SUCCESSFUL} - message sent successfully@* |
---|
| 542 | @code{@value{RPREFIX}INVALID_ID} - invalid queue id@* |
---|
| 543 | @code{@value{RPREFIX}INVALID_SIZE} - invalid message size@* |
---|
[f8892c9] | 544 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{buffer} is NULL@* |
---|
[f331481c] | 545 | @code{@value{RPREFIX}UNSATISFIED} - out of message buffers@* |
---|
| 546 | @code{@value{RPREFIX}TOO_MANY} - queue's limit has been reached |
---|
[ae68ff0] | 547 | |
---|
| 548 | @subheading DESCRIPTION: |
---|
| 549 | |
---|
| 550 | This directive sends the message buffer of size bytes |
---|
| 551 | in length to the queue specified by id. If a task is waiting on |
---|
| 552 | the queue, then the message is copied to the task's buffer and |
---|
| 553 | the task is unblocked. If no tasks are waiting on the queue, |
---|
| 554 | then the message is copied to a message buffer which is obtained |
---|
| 555 | from this message queue's message buffer pool. The message |
---|
| 556 | buffer is then placed at the front of the queue. |
---|
| 557 | |
---|
| 558 | @subheading NOTES: |
---|
| 559 | |
---|
| 560 | The calling task will be preempted if it has |
---|
| 561 | preemption enabled and a higher priority task is unblocked as |
---|
| 562 | the result of this directive. |
---|
| 563 | |
---|
| 564 | Sending a message to a global message queue which |
---|
| 565 | does not reside on the local node will generate a request |
---|
| 566 | telling the remote node to post the message on the specified |
---|
| 567 | message queue. |
---|
| 568 | |
---|
| 569 | If the task to be unblocked resides on a different |
---|
| 570 | node from the message queue, then the message is forwarded to |
---|
| 571 | the appropriate node, the waiting task is unblocked, and the |
---|
| 572 | proxy used to represent the task is reclaimed. |
---|
| 573 | |
---|
[169502e] | 574 | @c |
---|
| 575 | @c |
---|
| 576 | @c |
---|
[ae68ff0] | 577 | @page |
---|
| 578 | @subsection MESSAGE_QUEUE_BROADCAST - Broadcast N messages to a queue |
---|
| 579 | |
---|
[169502e] | 580 | @cindex broadcast message to a queue |
---|
| 581 | |
---|
[ae68ff0] | 582 | @subheading CALLING SEQUENCE: |
---|
| 583 | |
---|
[61389eac] | 584 | @ifset is-C |
---|
[169502e] | 585 | @findex rtems_message_queue_broadcast |
---|
[ae68ff0] | 586 | @example |
---|
| 587 | rtems_status_code rtems_message_queue_broadcast( |
---|
[ef47c44f] | 588 | rtems_id id, |
---|
| 589 | void *buffer, |
---|
| 590 | size_t size, |
---|
| 591 | uint32_t *count |
---|
[ae68ff0] | 592 | ); |
---|
| 593 | @end example |
---|
[61389eac] | 594 | @end ifset |
---|
| 595 | |
---|
| 596 | @ifset is-Ada |
---|
| 597 | @example |
---|
| 598 | procedure Message_Queue_Broadcast ( |
---|
| 599 | ID : in RTEMS.ID; |
---|
| 600 | Buffer : in RTEMS.Address; |
---|
| 601 | Size : in RTEMS.Unsigned32; |
---|
| 602 | Count : out RTEMS.Unsigned32; |
---|
| 603 | Result : out RTEMS.Status_Codes |
---|
| 604 | ); |
---|
| 605 | @end example |
---|
| 606 | @end ifset |
---|
[ae68ff0] | 607 | |
---|
| 608 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 609 | @code{@value{RPREFIX}SUCCESSFUL} - message broadcasted successfully@* |
---|
| 610 | @code{@value{RPREFIX}INVALID_ID} - invalid queue id@* |
---|
[f8892c9] | 611 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{buffer} is NULL@* |
---|
| 612 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{count} is NULL@* |
---|
[f331481c] | 613 | @code{@value{RPREFIX}INVALID_SIZE} - invalid message size |
---|
[ae68ff0] | 614 | |
---|
| 615 | @subheading DESCRIPTION: |
---|
| 616 | |
---|
| 617 | This directive causes all tasks that are waiting at |
---|
| 618 | the queue specified by id to be unblocked and sent the message |
---|
| 619 | contained in buffer. Before a task is unblocked, the message |
---|
| 620 | buffer of size byes in length is copied to that task's message |
---|
| 621 | buffer. The number of tasks that were unblocked is returned in |
---|
| 622 | count. |
---|
| 623 | |
---|
| 624 | @subheading NOTES: |
---|
| 625 | |
---|
| 626 | The calling task will be preempted if it has |
---|
| 627 | preemption enabled and a higher priority task is unblocked as |
---|
| 628 | the result of this directive. |
---|
| 629 | |
---|
| 630 | The execution time of this directive is directly |
---|
| 631 | related to the number of tasks waiting on the message queue, |
---|
| 632 | although it is more efficient than the equivalent number of |
---|
[75e22db] | 633 | invocations of @code{@value{DIRPREFIX}message_queue_send}. |
---|
[ae68ff0] | 634 | |
---|
| 635 | Broadcasting a message to a global message queue |
---|
| 636 | which does not reside on the local node will generate a request |
---|
| 637 | telling the remote node to broadcast the message to the |
---|
| 638 | specified message queue. |
---|
| 639 | |
---|
| 640 | When a task is unblocked which resides on a different |
---|
| 641 | node from the message queue, a copy of the message is forwarded |
---|
| 642 | to the appropriate node, the waiting task is unblocked, and the |
---|
| 643 | proxy used to represent the task is reclaimed. |
---|
| 644 | |
---|
[169502e] | 645 | @c |
---|
| 646 | @c |
---|
| 647 | @c |
---|
[ae68ff0] | 648 | @page |
---|
| 649 | @subsection MESSAGE_QUEUE_RECEIVE - Receive message from a queue |
---|
| 650 | |
---|
[169502e] | 651 | @cindex receive message from a queue |
---|
| 652 | |
---|
[ae68ff0] | 653 | @subheading CALLING SEQUENCE: |
---|
| 654 | |
---|
[61389eac] | 655 | @ifset is-C |
---|
[169502e] | 656 | @findex rtems_message_queue_receive |
---|
[ae68ff0] | 657 | @example |
---|
| 658 | rtems_status_code rtems_message_queue_receive( |
---|
[ef47c44f] | 659 | rtems_id id, |
---|
| 660 | void *buffer, |
---|
| 661 | size_t *size, |
---|
| 662 | uint32_t option_set, |
---|
| 663 | rtems_interval timeout |
---|
[ae68ff0] | 664 | ); |
---|
| 665 | @end example |
---|
[61389eac] | 666 | @end ifset |
---|
| 667 | |
---|
| 668 | @ifset is-Ada |
---|
| 669 | @example |
---|
| 670 | procedure Message_Queue_Receive ( |
---|
| 671 | ID : in RTEMS.ID; |
---|
| 672 | Buffer : in RTEMS.Address; |
---|
| 673 | Option_Set : in RTEMS.Option; |
---|
| 674 | Timeout : in RTEMS.Interval; |
---|
| 675 | Size : out RTEMS.Unsigned32; |
---|
| 676 | Result : out RTEMS.Status_Codes |
---|
| 677 | ); |
---|
| 678 | @end example |
---|
| 679 | @end ifset |
---|
[ae68ff0] | 680 | |
---|
| 681 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 682 | @code{@value{RPREFIX}SUCCESSFUL} - message received successfully@* |
---|
| 683 | @code{@value{RPREFIX}INVALID_ID} - invalid queue id@* |
---|
[f8892c9] | 684 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{buffer} is NULL@* |
---|
[7f46d43d] | 685 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{size} is NULL@* |
---|
[f331481c] | 686 | @code{@value{RPREFIX}UNSATISFIED} - queue is empty@* |
---|
| 687 | @code{@value{RPREFIX}TIMEOUT} - timed out waiting for message@* |
---|
| 688 | @code{@value{RPREFIX}OBJECT_WAS_DELETED} - queue deleted while waiting |
---|
[ae68ff0] | 689 | |
---|
| 690 | @subheading DESCRIPTION: |
---|
| 691 | |
---|
| 692 | This directive receives a message from the message |
---|
[f331481c] | 693 | queue specified in id. The @code{@value{RPREFIX}WAIT} and @code{@value{RPREFIX}NO_WAIT} options of the |
---|
[ae68ff0] | 694 | options parameter allow the calling task to specify whether to |
---|
| 695 | wait for a message to become available or return immediately. |
---|
| 696 | For either option, if there is at least one message in the |
---|
| 697 | queue, then it is copied to buffer, size is set to return the |
---|
| 698 | length of the message in bytes, and this directive returns |
---|
| 699 | immediately with a successful return code. |
---|
| 700 | |
---|
| 701 | If the calling task chooses to return immediately and |
---|
| 702 | the queue is empty, then a status code indicating this condition |
---|
| 703 | is returned. If the calling task chooses to wait at the message |
---|
| 704 | queue and the queue is empty, then the calling task is placed on |
---|
| 705 | the message wait queue and blocked. If the queue was created |
---|
[75e22db] | 706 | with the @code{@value{RPREFIX}PRIORITY} option specified, then |
---|
| 707 | the calling task is inserted into the wait queue according to |
---|
| 708 | its priority. But, if the queue was created with the |
---|
| 709 | @code{@value{RPREFIX}FIFO} option specified, then the |
---|
[ae68ff0] | 710 | calling task is placed at the rear of the wait queue. |
---|
| 711 | |
---|
| 712 | A task choosing to wait at the queue can optionally |
---|
| 713 | specify a timeout value in the timeout parameter. The timeout |
---|
| 714 | parameter specifies the maximum interval to wait before the |
---|
| 715 | calling task desires to be unblocked. If it is set to |
---|
[f331481c] | 716 | @code{@value{RPREFIX}NO_TIMEOUT}, then the calling task will wait forever. |
---|
[ae68ff0] | 717 | |
---|
| 718 | @subheading NOTES: |
---|
| 719 | |
---|
| 720 | The following message receive option constants are |
---|
| 721 | defined by RTEMS: |
---|
| 722 | |
---|
| 723 | @itemize @bullet |
---|
[f331481c] | 724 | @item @code{@value{RPREFIX}WAIT} - task will wait for a message (default) |
---|
| 725 | @item @code{@value{RPREFIX}NO_WAIT} - task should not wait |
---|
[ae68ff0] | 726 | @end itemize |
---|
| 727 | |
---|
| 728 | Receiving a message from a global message queue which |
---|
| 729 | does not reside on the local node will generate a request to the |
---|
| 730 | remote node to obtain a message from the specified message |
---|
[f331481c] | 731 | queue. If no message is available and @code{@value{RPREFIX}WAIT} was specified, then |
---|
[ae68ff0] | 732 | the task must be blocked until a message is posted. A proxy is |
---|
| 733 | allocated on the remote node to represent the task until the |
---|
| 734 | message is posted. |
---|
| 735 | |
---|
[1ca951ce] | 736 | A clock tick is required to support the timeout functionality of |
---|
| 737 | this directive. |
---|
| 738 | |
---|
[169502e] | 739 | @c |
---|
| 740 | @c |
---|
| 741 | @c |
---|
[ae68ff0] | 742 | @page |
---|
[d1f19f0] | 743 | @subsection MESSAGE_QUEUE_GET_NUMBER_PENDING - Get number of messages pending on a queue |
---|
| 744 | |
---|
[169502e] | 745 | @cindex get number of pending messages |
---|
| 746 | |
---|
[d1f19f0] | 747 | @subheading CALLING SEQUENCE: |
---|
| 748 | |
---|
| 749 | @ifset is-C |
---|
[169502e] | 750 | @findex rtems_message_queue_get_number_pending |
---|
[d1f19f0] | 751 | @example |
---|
| 752 | rtems_status_code rtems_message_queue_get_number_pending( |
---|
[ef47c44f] | 753 | rtems_id id, |
---|
| 754 | uint32_t *count |
---|
[d1f19f0] | 755 | ); |
---|
| 756 | @end example |
---|
| 757 | @end ifset |
---|
| 758 | |
---|
| 759 | @ifset is-Ada |
---|
| 760 | @example |
---|
| 761 | procedure Message_Queue_Get_Number_Pending ( |
---|
| 762 | ID : in RTEMS.ID; |
---|
| 763 | Count : out RTEMS.Unsigned32; |
---|
| 764 | Result : out RTEMS.Status_Codes |
---|
| 765 | ); |
---|
| 766 | @end example |
---|
| 767 | @end ifset |
---|
| 768 | |
---|
| 769 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 770 | @code{@value{RPREFIX}SUCCESSFUL} - number of messages pending returned successfully@* |
---|
[f8892c9] | 771 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{count} is NULL@* |
---|
[f331481c] | 772 | @code{@value{RPREFIX}INVALID_ID} - invalid queue id |
---|
[d1f19f0] | 773 | |
---|
| 774 | @subheading DESCRIPTION: |
---|
| 775 | |
---|
| 776 | This directive returns the number of messages pending on this |
---|
| 777 | message queue in count. If no messages are present |
---|
| 778 | on the queue, count is set to zero. |
---|
| 779 | |
---|
| 780 | @subheading NOTES: |
---|
| 781 | |
---|
| 782 | Getting the number of pending messages on a global message queue which |
---|
| 783 | does not reside on the local node will generate a request to the |
---|
| 784 | remote node to actually obtain the pending message count for |
---|
| 785 | the specified message queue. |
---|
| 786 | |
---|
| 787 | |
---|
[169502e] | 788 | @c |
---|
| 789 | @c |
---|
| 790 | @c |
---|
[d1f19f0] | 791 | @page |
---|
[ae68ff0] | 792 | @subsection MESSAGE_QUEUE_FLUSH - Flush all messages on a queue |
---|
| 793 | |
---|
[169502e] | 794 | @cindex flush messages on a queue |
---|
| 795 | |
---|
[ae68ff0] | 796 | @subheading CALLING SEQUENCE: |
---|
| 797 | |
---|
[61389eac] | 798 | @ifset is-C |
---|
[169502e] | 799 | @findex rtems_message_queue_flush |
---|
[ae68ff0] | 800 | @example |
---|
| 801 | rtems_status_code rtems_message_queue_flush( |
---|
[ef47c44f] | 802 | rtems_id id, |
---|
| 803 | uint32_t *count |
---|
[ae68ff0] | 804 | ); |
---|
| 805 | @end example |
---|
[61389eac] | 806 | @end ifset |
---|
| 807 | |
---|
| 808 | @ifset is-Ada |
---|
| 809 | @example |
---|
| 810 | procedure Message_Queue_Flush ( |
---|
| 811 | ID : in RTEMS.ID; |
---|
| 812 | Count : out RTEMS.Unsigned32; |
---|
| 813 | Result : out RTEMS.Status_Codes |
---|
| 814 | ); |
---|
| 815 | @end example |
---|
| 816 | @end ifset |
---|
[ae68ff0] | 817 | |
---|
| 818 | @subheading DIRECTIVE STATUS CODES: |
---|
[f331481c] | 819 | @code{@value{RPREFIX}SUCCESSFUL} - message queue flushed successfully@* |
---|
[f8892c9] | 820 | @code{@value{RPREFIX}INVALID_ADDRESS} - @code{count} is NULL@* |
---|
[f331481c] | 821 | @code{@value{RPREFIX}INVALID_ID} - invalid queue id |
---|
[ae68ff0] | 822 | |
---|
| 823 | @subheading DESCRIPTION: |
---|
| 824 | |
---|
| 825 | This directive removes all pending messages from the |
---|
| 826 | specified queue id. The number of messages removed is returned |
---|
| 827 | in count. If no messages are present on the queue, count is set |
---|
| 828 | to zero. |
---|
| 829 | |
---|
| 830 | @subheading NOTES: |
---|
| 831 | |
---|
| 832 | Flushing all messages on a global message queue which |
---|
| 833 | does not reside on the local node will generate a request to the |
---|
| 834 | remote node to actually flush the specified message queue. |
---|
| 835 | |
---|