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Re: Frustration with changing lock type

by crabbdean (Pilgrim)
on Apr 14, 2004 at 12:20 UTC ( #345012=note: print w/ replies, xml ) Need Help??


in reply to Frustration with changing lock type

Yeah, there is a race condition there but in that race if another process grabs the file wouldn't it then have the lock, putting the other one into wait mode? Personally I'd avoid the LOCK_SH and just go for LOCK_EX, write what you need and release (LOCK_UN). You're talking a millisecond of time really.

I once wanted to test such a thing so I created a quick module that was called by a script to lock, and release a DB database. I then proceeced to run about 6 copies of my script at once. They went crazy locking and unlocking and only had to wait for lock every few hundred goes, and even then it was only for a fraction of a second. I was all rather impressed at the time seeing 6 copies trying to grab it a few hundred times a second. Anyway, the moral is ... well you get the gist.


Dean
The Funkster of Mirth
Programming these days takes more than a lone avenger with a compiler. - sam
RFC1149: A Standard for the Transmission of IP Datagrams on Avian Carriers


Comment on Re: Frustration with changing lock type
Re^2: Frustration with changing lock type
by demerphq (Chancellor) on Apr 14, 2004 at 12:45 UTC

    Well speed isnt the issue here so much. The tasks being performed are mostly file moves/ftp and transformations of large files, so the actual taks could take minutes to complete or possible longer in some circumstances. I know I cold have gone with a simpler design if I didnt want to know who owned the task already, but once you set yourself a goal....

    Cheers for the reply.


    ---
    demerphq

      First they ignore you, then they laugh at you, then they fight you, then you win.
      -- Gandhi


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