Re: Multi-threading access to device drivers.

From: Poul-Henning Kamp (phk_at_phk.freebsd.dk)
Date: 11/07/04

  • Next message: Poul-Henning Kamp: "Re: Multi-threading access to device drivers." 
    To: Matthew Dillon <dillon@apollo.backplane.com>
Date: Sun, 07 Nov 2004 08:48:39 +0100

    In message <200411070357.iA73vaqU040765@apollo.backplane.com>, Matthew Dillon writes:
    >:As was quoted POSIX, the update should be atomic.. so my reading of
    >:that is that you lock the fd, when you read the offset from the fd,
    >:you need to also update the offset with the number of bytes read, so
    >:that a racing read both doesn't drop any data, nor duplicate any data..
    >:
    >:i.e. single file with fixed records, it should be perfectly safe to
    >:throw five threads looping doing a read processing of the records w/o
    >:fear of duplicate records, or dropped records...
    >:
    >:And if we handle it in this manner, then you can allow multiple reads
    >:into the driver...
    >:
    >:--
    >: John-Mark Gurney Voice: +1 415 225 5579
    >
    > If it's a regular file [...]

    BZZZT! Wrong, but thanks for playing. (We are talking devices here) 

    -- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.
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  • Next message: Poul-Henning Kamp: "Re: Multi-threading access to device drivers."

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