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/coremsgclose.c | 23 +++++++++++++++++------ cpukit/score/src/coremsgflush.c | 4 ++-- cpukit/score/src/coremsgflushsupp.c | 27 +++++++++++++++++++++++++++ 3 files changed, 46 insertions(+), 8 deletions(-) (limited to 'cpukit/score/src') diff --git a/cpukit/score/src/coremsgclose.c b/cpukit/score/src/coremsgclose.c index 552c0dc477..245c18524f 100644 --- a/cpukit/score/src/coremsgclose.c +++ b/cpukit/score/src/coremsgclose.c @@ -50,15 +50,26 @@ void _CORE_message_queue_Close( unsigned32 status ) { + + /* + * This will flush blocked threads whether they were blocked on + * a send or receive. + */ + + _Thread_queue_Flush( + &the_message_queue->Wait_queue, + remote_extract_callout, + status + ); + + /* + * 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 ); - else - _Thread_queue_Flush( - &the_message_queue->Wait_queue, - remote_extract_callout, - status - ); (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 --- a/cpukit/score/src/coremsgflush.c +++ b/cpukit/score/src/coremsgflush.c @@ -33,8 +33,8 @@ * * _CORE_message_queue_Flush * - * 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 --- 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