Getting Started with QNX Neutrino - QNX Software Systems

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send a message
send hierarchy
server
signal
sporadic
synchronous
thread
A thread can send a message to another thread. The MsgSend*() series of functions
are used to send the message; the sending thread blocks until the receiving thread
replies to the message. See Message passing. A thread that sends a message is said
to be a Client.
A design paradigm whereby messages sent flow in one direction, and messages
replied to flow in another direction. The primary purpose of having a send hierarchy
is to avoid deadlock. A send hierarchy is accomplished by assigning clients and
servers a “level,” and ensuring that messages that are being sent go only to a higher
level. This avoids the potential for deadlock where two threads would send to each
other, because it would violate the send hierarchy — one thread should not have sent
to the other thread, as that other thread must have been at a lower level.
A server is a regular, user-level process that provides certain types of functionality
(usually file-descriptor-based) to clients. Servers are typically Resource Managers,
and there’s an extensive library provided by QSS which performs much of the
functionality of a resource manager for you. The server’s job is to receive messages
from clients, process them, and then reply to the messages, which unblocks the
clients. A thread can be both a client and a server at the same time.
A mechanism dating back to early UNIX systems that is used to send asynchronous
notification of events from one thread to another. Signals are non-blocking for the
sender. The receiver of the signal may decide to treat the signal in a synchronous
manner by explicitly waiting for it. Contrast with pulse.
Scheduling algorithm whereby a thread’s priority can oscillate dynamically between a
“foreground” or normal priority and a “background” or low priority. A thread is given
an execution budget of time to be consumed within a certain replenishment period.
See also FIFO and round robin.
Used to indicate that a given operation has some synchronization to another operation.
For example, during a message-passing operation, when the server does a
MsgReply() (to reply to the client), the unblocking of the client is said to be
synchronous to the reply operation. Contrast with Asynchronous.
A single, schedulable, flow of execution. Threads are implemented directly within the
Neutrino kernel and correspond to the POSIX pthread*() function calls. A thread will
need to synchronize with other threads (if any) by using various synchronization
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