 03 Jan 2019, Konstantin Olchanski, Info, 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:
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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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> > > > > > > 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:
>
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 29 Sep 2021, Richard Longland, Bug Report, nstall clash between MIDAS 2020-08 and mscb
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Thank you, Stefan.
I found these instructions under
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29 Sep 2021, Stefan Ritt, Bug Report, nstall clash between MIDAS 2020-08 and mscb
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> Thank you, Stefan.
>
> I found these instructions under
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28 Jan 2024, Pavel Murat, Forum, number of entries in a given ODB subdirectory ?
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Dear MIDAS experts,
- I have a detector configuration with a variable number of hardware components - FPGA's receiving data
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28 Jan 2024, Konstantin Olchanski, Forum, number of entries in a given ODB subdirectory ?
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Very good question. It exposes a very nasty problem, the race condition between "ls" and "rm". While you are
looping over directory entries, somebody else is completely permitted to remove one of the files (or add more
files), making the output of "ls" incorrect (contains non-existant/removed files, does not contain newly added
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28 Jan 2024, Stefan Ritt, Forum, number of entries in a given ODB subdirectory ? 
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I guess you won't change your FPGA configuration just when you start a run, so I don't consider the race
condition very crucial (although KO is correct, it it there).
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29 Jan 2024, Pavel Murat, Forum, number of entries in a given ODB subdirectory ?
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Hi Stefan, Konstantin,
thanks a lot for your responses - they are very teaching and it is good to have them archived in the forum.
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29 Jan 2024, Konstantin Olchanski, Forum, number of entries in a given ODB subdirectory ?
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> https://chat.openai.com/share/d927c78d-9914-4413-ab5e-3b0e5d173132
>
> Please note that you never can be 100% sure that the code from a LLM is correct
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03 Feb 2024, Pavel Murat, Forum, number of entries in a given ODB subdirectory ?
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Konstantin is right: KEY.num_values is not the same as the number of subkeys (should it be ?)
For those looking for an example in the future, I attach a working piece of code converted
from the ChatGPT example, together with its printout.
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08 Feb 2024, Stefan Ritt, Forum, number of entries in a given ODB subdirectory ?
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> Konstantin is right: KEY.num_values is not the same as the number of subkeys (should it be ?)
For ODB keys of type TID_KEY, the value num_values IS the number of subkeys. The only issue here is
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11 Feb 2024, Pavel Murat, Forum, number of entries in a given ODB subdirectory ?
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> For ODB keys of type TID_KEY, the value num_values IS the number of subkeys.
this logic makes sense, however it doesn't seem to be consistent with the printout of the test example
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13 Feb 2024, Stefan Ritt, Forum, number of entries in a given ODB subdirectory ?
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> > For ODB keys of type TID_KEY, the value num_values IS the number of subkeys.
>
> this logic makes sense, however it doesn't seem to be consistent with the printout of the test example
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15 Feb 2024, Konstantin Olchanski, Forum, number of entries in a given ODB subdirectory ?
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> > > For ODB keys of type TID_KEY, the value num_values IS the number of subkeys.
> >
> > this logic makes sense, however it doesn't seem to be consistent with the printout of the test example
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15 Feb 2024, Konstantin Olchanski, Forum, number of entries in a given ODB subdirectory ?
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> > You are right, num_values is always 1 for TID_KEYS. The number of subkeys is stored in
> > ((KEYLIST *) ((char *)pheader + pkey->data))->num_keys
> > Maybe we should add a function to return this. But so far db_enum_key() was enough.
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15 Feb 2024, Stefan Ritt, Forum, number of entries in a given ODB subdirectory ?
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> Hmm... is there any use case where you want to know the number of directory entries, but you will not iterate
> over them later?
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19 Feb 2024, Pavel Murat, Forum, number of entries in a given ODB subdirectory ?
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> > Hmm... is there any use case where you want to know the number of directory entries, but you will not iterate
> > over them later?
>
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01 Jan 2009, Konstantin Olchanski, Info, odb "hot link" magic explored
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Here are my notes on the MIDAS ODB "hot link" function. Perhaps others can find them useful.
Using db_open_record(key,function), the user can tell MIDAS to call the specified user function when
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14 Jan 2009, Stefan Ritt, Info, odb "hot link" magic explored
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[quote="KO"]note 1: I do not completely understand the ss_suspend_xxx() stuff. The best I can tell is it creates a number of udp sockets bound to the local
host and at least one udp rpc receive socket ultimately connected to the cm_dispatch_rpc() function.[/quote]
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23 Dec 2010, Konstantin Olchanski, Bug Report, odb corruption, odb race condition?
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The following script makes midas very unhappy and eventually causes odb corruption. I suspect the reason is some kind of race condition collision between
client
creation and destruction code and the watchdog activity (each client periodically runs cm_watchdog() to check if other clients are still alive, O(NxN) |