Re: Sequence monitor not getting callback

[Benjamin Franksen <benjamin.franksen@helmholtz-berlin.de>]

Am Freitag, 16. September 2011, um 00:50:04 schrieb Zelazny, Michael Stanley:
> >From time to time it appears as though my sequences don't get their monitor
callbacks.  Example:
> #42 of 196:
> Channel name: "KLYS:LI27:51:BVLT"
>   Unexpanded (assigned) name: ""
>   Variable name: "BVLT"
>     address = 203186364 = 0xc1c60bc
>     type = float
>     count = 1
>   Value = 0
>   Monitor flag = 0
>     Monitored
>   Assigned
>   Connected
>   Get not completed or no get issued
>   Put not completed or no put issued
>   Status = 0
>   Severity = 0
>   Message =
>   Time stamp = 2011/09/15 14:46:40.940
> Next? (+/- skip count)
>
> $ caget KLYS:LI27:51:BVLT KLYS:LI27:51:BVLT.MDEL
> KLYS:LI27:51:BVLT              349.717
> KLYS:LI27:51:BVLT.MDEL         0
>
> The PV is assigned with pvAssign and monitored with pvMonitor.
>
> The PV lives on the same soft ioc as the sequence.
>
> epics> dbpr("KLYS:LI27:51:BVLT",1000)
> ACKS: MAJOR         ACKT: YES           ADEL: 0             ALST:
> 350.166015625 AOFF: 0             ASG:                ASLO: 0
> ASP: 0xa7acfe8 BKPT: 00            DESC: Beam Voltage  DISA: 0
> DISP: 0 DISS: NO_ALARM      DISV: 1             DOL:CONSTANT        DPVT:
> (nil) DRVH: 0             DRVL: 0             DSET: 0x6bf280      DTYP:
> Soft Channel EGU:                EGUF: 0             EGUL: 0
> EOFF: 0 ESLO: 1             EVNT: 0             FLNK:DB_LINK
> KLYS:LI27:51:BVLTTS HHSV: NO_ALARM      HIGH: 360.000152587891
>      HIHI: 0 HOPR: 0             HSV: MAJOR          HYST: 0
> INIT: 0 IVOA: Continue normally                 IVOV: 0             LALM:
> 350.166015625 LBRK: 0             LCNT: 0             LINR: NO CONVERSION
> LLSV: NO_ALARM LOLO: 0             LOPR: 0             LOW: 0
> LSET: 0xb7b25dc8 LSV: NO_ALARM       MDEL: 0
> MLIS: 40 0a 70 8a d0 58 5b 0e 03 00 00 00                   MLOK: c8 b8 f0
> 09 MLST: 350.166015625 NAME: KLYS:LI27:51:BVLT                 NSEV:
> NO_ALARM NSTA: NO_ALARM      OIF: Full           OMOD: 0             OMSL:
> supervisory ORAW: 350           ORBV: 0             OROC: 0
> OUT:CONSTANT OVAL: 350.166015625 PACT: 0             PBRK: (nil)
> PHAS: 0 PINI: YES           PPN: (nil)          PPNR: (nil)         PREC:
> 6 PRIO: LOW           PROC: 0             PUTF: 0             PVAL:
> 350.166015625 RBV: 0              RDES: 0x81bbc50     ROFF: 0
> RPRO: 0 RSET: 0xf66840      RVAL: 350           SCAN: Passive
> SDIS:CONSTANT SEVR: NO_ALARM      SIML:CONSTANT       SIMM: NO
> SIMS: NO_ALARM SIOL:CONSTANT       SPVT: (nil)         STAT: NO_ALARM
> TIME: 2011-09-15 14:58:57.976294000     TPRO: 0             TSE: 0
> TSEL:CONSTANT       UDF: 0              VAL: 350.166015625
>
> More than 99% of the time, the sequence works great, but with 85 klystrons
> in SLAC's LCLS I see about 1 failure per month.  When the sequence starts
> one of its PVs appears to never get any callbacks.  If I restart the
> sequence, everything is fine.
>
> Using EPICS 3.14.12, sequencer 2.0.11, OS RHEL 4, update 8.
>
> Q: Has anyone else seen this?  If so, how did you fix it?
>
> I'm considering upgrading my sequencer to 2.1.2 based on Ben Franksen's
> notes about fixing bugs in pvAssign and "Safe mode".

I don't think use of pvAssign has anything to do with the problem (but I could
be wrong). Whether safe mode helps depends on whether access to a 'float' value
might be non-atomic on the system (OS, arch) on which your IOC and SNL program
run. Thus I need more data before I can judge conclusively.

I have heard the same complaint form at least one other user: sometimes
(monitor) events that should happen simply don't. I cannot guarantee that the
latest release (2-1-2) does not contain this or a similar bug. But the
internal workings of the sequencer have been cleaned up quite a bit since the
2-0-x versions, so it may well be that simply switching to the new version
fixes the problem. In any case, if it does /not/ do that, I can guaranteed that
I will be highly motivated to find out the reason for this and fix it ASAP.

Cheers
Ben

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