From 9c1c778d56ef42f8f00dbd87b2bcf2293bf49380 Mon Sep 17 00:00:00 2001 From: Jennifer Averett Date: Thu, 13 Jan 2000 18:32:38 +0000 Subject: + Added comments --- cpukit/score/src/coremsgflushsupp.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) (limited to 'cpukit/score/src/coremsgflushsupp.c') diff --git a/cpukit/score/src/coremsgflushsupp.c b/cpukit/score/src/coremsgflushsupp.c index f221be000e..4bfd8f358b 100644 --- a/cpukit/score/src/coremsgflushsupp.c +++ b/cpukit/score/src/coremsgflushsupp.c @@ -57,6 +57,33 @@ unsigned32 _CORE_message_queue_Flush_support( Chain_Node *message_queue_last; unsigned32 count; + /* + * 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; -- cgit v1.2.3