Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.sys.apple2.programmer > #3429

Calling Marinetti from an init

Show all headers | View raw

I'm working on a IIgs system extension (an init) that uses TCP/IP. I 
would like it to be able to continually poll for incoming data and send 
responses as long as GS/OS is running (regardless of the current 
application), but I don't see an entirely satisfactory way to do that.

The basic issue is that it doesn't seem to be safe to call Marinetti 
using interrupt-based timers (e.g. from a heartbeat task). This may 
appear to work as long as nothing else is using Marinetti, but if 
something else is, then I get dropped connections and other odd 
behavior. I think this is because my code may wind up calling Marinetti 
while the other program is also in the middle of a Marinetti call, and 
since Marinetti is not (fully) reentrant this corrupts its state.

My understanding is that it's generally safe to make most tool calls in 
such situations if the system busy flag is not set (and if it is set 
then the scheduler can be used to defer the operation until it's not), 
but this doesn't seem to make a difference with Marinetti. As far as I 
can tell from looking at the MOSP code, Marinetti never increments the 
busy flag, so it's not surprising that this doesn't work.

My current workaround for this issue is to use a run queue task 
instead. This more or less works in desktop programs, but it doesn't 
work in other environments like textual shells, because they don't call 
SystemTask and therefore run queue tasks don't get run. (There can also 
be an issue if a desktop program is busy with something and doesn't 
call SystemTask for a long time.)

Am I missing some good way to do what I want? If not, should Marinetti 
be changed to make this possible? I think at a minimum it would have to 
be modified to increment the busy flag around any non-reentrant 
sections of code. It seems like this would be useful for a fairly wide 
range of programs, including servers and programs that provide some 
kind of system service using a TCP/IP connection.

-- 
Stephen Heumann

Back to comp.sys.apple2.programmer | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

Calling Marinetti from an init Stephen Heumann <stephen.heumann@gmail.com> - 2017-04-20 22:53 -0500
  Re: Calling Marinetti from an init andrew.roughan@writeme.com - 2017-05-02 16:58 -0700
    Re: Calling Marinetti from an init andrew.roughan@writeme.com - 2017-05-02 17:03 -0700
    Re: Calling Marinetti from an init Stephen Heumann <stephen.heumann@gmail.com> - 2017-05-02 21:13 -0500

csiph-web