|author||Jennifer Averett <Jennifer.Averett@OARcorp.com>||2000-01-13 18:32:38 +0000|
|committer||Jennifer Averett <Jennifer.Averett@OARcorp.com>||2000-01-13 18:32:38 +0000|
+ Added comments
Diffstat (limited to 'cpukit/score/src')
3 files changed, 46 insertions, 8 deletions
diff --git a/cpukit/score/src/coremsgclose.c b/cpukit/score/src/coremsgclose.c
index 552c0dc477..245c18524f 100644
@@ -50,15 +50,26 @@ void _CORE_message_queue_Close(
+ * This will flush blocked threads whether they were blocked on
+ * a send or receive.
+ * This removes all messages from the pending message queue. Since
+ * we just flushed all waiting threads, we don't have to worry about
+ * the flush satisfying any blocked senders as a side-effect.
if ( the_message_queue->number_of_pending_messages != 0 )
(void) _CORE_message_queue_Flush_support( the_message_queue );
(void) _Workspace_Free( the_message_queue->message_buffers );
diff --git a/cpukit/score/src/coremsgflush.c b/cpukit/score/src/coremsgflush.c
index f11ed065b6..957d00a59e 100644
@@ -33,8 +33,8 @@
- * This function flushes the message_queue's task wait queue. The number
- * of messages flushed from the queue is returned.
+ * This function flushes the message_queue's pending message queue. The
+ * number of messages flushed from the queue is returned.
* Input parameters:
* the_message_queue - the message_queue to be flushed
diff --git a/cpukit/score/src/coremsgflushsupp.c b/cpukit/score/src/coremsgflushsupp.c
index f221be000e..4bfd8f358b 100644
@@ -57,6 +57,33 @@ unsigned32 _CORE_message_queue_Flush_support(
+ * Currently, RTEMS supports no API that has both flush and blocking
+ * sends. Thus, this routine assumes that there are no senders
+ * blocked waiting to send messages. In the event, that an API is
+ * added that can flush a message queue when threads are blocked
+ * waiting to send, there are two basic behaviors envisioned:
+ * (1) The thread queue of pending senders is a logical extension
+ * of the pending message queue. In this case, it should be
+ * flushed using the _Thread_queue_Flush() service with a status
+ * such as CORE_MESSAGE_QUEUE_SENDER_FLUSHED (which currently does
+ * not exist). This can be implemented without changing the "big-O"
+ * of the message flushing part of the routine.
+ * (2) Only the actual messages queued should be purged. In this case,
+ * the blocked sender threads must be allowed to send their messages.
+ * In this case, the implementation will be forced to individually
+ * dequeue the senders and queue their messages. This will force
+ * this routine to have "big O(n)" where n is the number of blocked
+ * senders. If there are more messages pending than senders blocked,
+ * then the existing flush code can be used to dispose of the remaining
+ * pending messages.
+ * For now, though, we are very happy to have a small routine with
+ * fixed execution time that only deals with pending messages.
_ISR_Disable( level );
inactive_first = the_message_queue->Inactive_messages.first;
message_queue_first = the_message_queue->Pending_messages.first;