 04 Jun 2009, Stefan Ritt, Bug Report, odbedit bad ctrl-C
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> When using "/bin/bash" shell, if I exit odbedit (and other midas programs) using ctrl-C, the terminal
> enters a funny state, "echo" is turned off (I cannot see what I type), "delete" key does not work (echoes
> ^H instead).
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18 Feb 2009, Konstantin Olchanski, Info, odbc sql history mlogger update
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> mhttpd and mlogger have been updated with potentially troublesome changes.
> These new features are now available:
> - a "feature complete" implementation of "history in an SQL database".
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 20 Feb 2019, Konstantin Olchanski, Info, odb needs protection against ctrl-c
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Even with the cm_watchdog signal removed, some trouble from UNIX signals remains.
This time, when one presses Ctrl-C at the wrong time, the Ctrl-C signal handler will run at the wrong time
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20 Feb 2019, Stefan Ritt, Info, odb needs protection against ctrl-c
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Not sure if you realized, but there is a two-stage Ctrl-C handling inside midas. The first time you hit ctrl-c, the handler just sets a flag for the main
event loop, so that the program can gracefully exit without trouble. This is
done inside cm_ctrlc_handler(), which sets _ctrlc_pressed true if called. Then cm_yield() tests this flag and returns RPC_SHUTDOWN if so. I agree not very |
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20 Feb 2019, Konstantin Olchanski, Info, odb needs protection against ctrl-c
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Commit f81ff3c protects db_lock/unlock, but not any of the other functions. What if we do ctrl-c in the middle
of some odb write operation in the middle of memory allocation, etc.
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20 Feb 2019, Konstantin Olchanski, Info, odb needs protection against ctrl-c
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> Not sure if you realized, but there is a two-stage Ctrl-C handling inside midas.
Hmm... I am looking at the ctrl-c handler inside odbedit.
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20 Feb 2019, Stefan Ritt, Info, odb needs protection against ctrl-c
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Have you read what I wrote? The current ctrl-c handler just sets the _ctrlc_pressed flag. It might be that some programs do not correctly interprete the
return of cm_yield(), certainly the frontend does it correctly. On the SECOND ctrl-c, the program gets
(internally) hard aborted, equivalent to calling abort(). Not sure if the code works everywhere, I see now that cm_yield(() should maybe return SS_ABORT |
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13 Oct 2017, Konstantin Olchanski, Info, odb multithread support repaired
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multithreaded access to odb was implemented back in 2013-2014. but recently a bug surfaced -
there was a race condition in the odb locking code against cm_watchdog(). Somehow this only
affected the mserver for the DRAGON experiment at TRIUMF. This is now fixed on the branch
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08 Aug 2022, Konstantin Olchanski, Info, odb disallow key names that start or end with spaces
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while testing the new odb editor, we ran into a number of problems with key names
that start or end with spaces. we cannot think of any valid use case for such key
names (subdirectories and variables) and we think they could only have been
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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) |
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24 Dec 2010, Konstantin Olchanski, Bug Report, odb corruption, odb race condition?
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> Thu Dec 23 12:10:30 2010 [ODBEdit9,ERROR] [odb.c:3247:db_get_value,ERROR] "Name" is of type NULL, not STRING
This is caused by a race condition between client removal in cm_delete_client_info() and cm_exist().
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24 Dec 2010, Konstantin Olchanski, Bug Report, odb corruption, odb race condition?
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> > Thu Dec 23 12:10:30 2010 [ODBEdit9,ERROR] [odb.c:3247:db_get_value,ERROR] "Name" is of type NULL, not STRING
> This is caused by a race condition between client removal in cm_delete_client_info() and cm_exist().
> ... this race condition seems to be benign.
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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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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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