Re: [hpoj-devel] Laserjet 1220 hangs on the second job - possible cause

[Cory M. <cor...@hp...>]

Thx for your effort on this... I have forwarded your suggestions on to
the developers.

Cory
hp linux printing team

On Thu, 2004-08-05 at 16:17, Tomasz Malesinski wrote:
> I have the same problem as the one mentioned at the end of the
> message:
> 
> http://sourceforge.net/mailarchive/message.php?msg_id=2306606
> 
> The difference is that the problem happens almost always on my
> system. After I print one job and I send another one, the printer
> usually hangs as described in the mentioned message. I suspect that
> this is caused by a race condition, so whether the printer hangs or
> not may depend on computer speed, CPU load etc.
> 
> I have Intel Pentium III 800 MHz CPU running Debian Woody. I use CUPS
> as a spooler. I have HP Laserjet 1220 connected via USB.
> 
> When I investigated the problem, I was using sources from CVS.
> I was printing files using ptal-print this way:
> 
> ptal-print <test.prn
> 
> where test.prn was a CUPS output for some postscript file. I tried it
> also with Windows drivers output.
> 
> The suspected race condition goes as follows:
> 
> - ptal-print sends the job, job data are buffered waiting for ptal-mlcd
>   to receive them
> - after sending all the data, ptal-print closes a socket and exits
> - ptal-mlcd receives part of the job data
> - as ptal-mlcd has some reverse data from the previous job (it ended
>   with @PJL ECHO EOJ), it tries to send it to ptal-print
> - the connection to ptal-print is broken, so ptal-mlcd receives
>   SIGPIPE, write failes and (in ExMgr::sessionServiceOutput) it
>   duplicates the /dev/null file descriptor in place of the session
>   socket
> - ptal-mlcd hits EOF on /dev/null when trying to receive the rest of
>   the job and the printer does not receive the entire job
> 
> I have been redirecting data read in ExMgr::pullForwardData to a file
> and the second job was in fact truncated there.
> 
> I commented out nullDup call in ExMgr::sessionServiceOutput and
> everything started to work fine. I have not yet written a more elegant
> solution, but it seems that after a failed write to a session socket,
> ptal-mlcd should continue to read from the socket, but drop buffers
> waiting to be written to it and all the buffers that will be added to
> pReverseBdrQueue later.
> 
> Tomasz Malesinski
> 
> 
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