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 28 Dec 2018, Konstantin Olchanski, Info, note on the midas event buffer code, part 1
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 28 Dec 2018, Konstantin Olchanski, Info, note on the midas event buffer code, part 2, bm_send_event()
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28 Dec 2018, Konstantin Olchanski, Info, note on the midas event buffer code, part 3, rpc_send_event()
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28 Dec 2018, Konstantin Olchanski, Info, note on the midas event buffer code, part 4, reading from event buffer
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02 Jan 2019, Konstantin Olchanski, Info, note on the midas event buffer code, part 5, bm_read_buffer()
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02 Jan 2019, Konstantin Olchanski, Info, note on the midas event buffer code, part 6, reading events through the mserver
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03 Jan 2019, Konstantin Olchanski, Info, note on the midas event buffer code, part 7, event buffer polling frequencies
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03 Jan 2019, Konstantin Olchanski, Info, note on the midas event buffer code, part 8, writer and reader communications
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10 Jan 2019, Konstantin Olchanski, Info, note on the midas event buffer code, part 8, writer and reader communications
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Message ID: 1434
Entry time: 10 Jan 2019
In reply to: 1433
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| Author: |
Konstantin Olchanski |
| Topic: |
Info |
| Subject: |
note on the midas event buffer code, part 8, writer and reader communications |
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> > > > > > > In this technical note, I write down the workings of the midas event buffer code
> Event buffer readers and writers need to communicate following information:
>
> N.B.1. There is a fly in the ointment for the writer-to-reader path: a function called
> bm_mark_read_waiting() is called from several places to set and clear the reader "read_wait" flag.
> I think this causes several logic errors...
bm_mark_read_waiting() is removed in the new code, it is unnecessary. This uncovered a number of problems
in the writer-to-reader communications, fixed in the new code:
- bm_poll_event() did not poll anything because internal flags were not set right
- reader "read_wait" now means "I am waiting for new data, please send me a notification "B" message".
- writer sends a notification "B" message and clears "read_wait" to stop sending more notifications until the reader asks for more data.
- for remote clients, there is interplay between the 500 ms sec blank-off in sending BM_MSG notifications from the mserver and the 1000 ms timeout in the loop of bm_poll_event(). Do not
change one of them without thinking how it will affect the other one and how they interact.
K.O. |