message_queue delays

[eran <eran@…>]

Hello,

I've encountered an issue with send/receive delays while using interprocess::message_queue.

Although mostly it takes 1-2 microseconds to send/receive a message, about 5% of the messages are delayed for 1-2 milliseconds.

It seems that at revision 34837 (Aug06), which was a major update, the lines that check for 'was_empty' and 'was_full' before using the condition's notify, were commented out.

Fix: I've uncommented those lines and everything seems fine now - no delays. Also, this seems to fix another issue in my platform (Win7) - a forceful shutdown of a client using message_queue caused, sometimes, a termination of the server. (again, related to the condition variable)

Attached a diff file for this fix.