Re: 4-stable termios diff behaviour lc/lc_r

From: Tijl Coosemans (tijl_at_ulyssis.org)
Date: 08/30/04

  • Next message: Don Lewis: "Re: 4-stable termios diff behaviour lc/lc_r" 
    Date: Mon, 30 Aug 2004 20:45:53 +0200
To: freebsd-stable@freebsd.org

    Original message on -questions, but this list seems more appropriate.
    More below.

    On Sun, 29 Aug 2004 11:35:39 +0200, Tijl Coosemans wrote:

    > Hi list,
    >
    > I think I've found a possible bug in 4-stable, though I'm not that
    > kind of an expert so I'll leave that decision up to you.
    >
    > Attached is a little test program that opens /dev/cuaa0 and tries to
    > read a couple bytes.
    >
    > When compiled using "gcc vtime.c -o vtime" there's no problem. For
    > example, when you run vtime without anything attached to cuaa0,
    > it'll wait about 2 seconds and timeout, since VMIN=0 and VTIME=20.
    >
    > When compiled using "gcc -pthread vtime.c -o vtime" however, the
    > read function returns immediately, which as far as I can understand,
    > is not what it's supposed to do.
    >
    > Does anyone know if this intended or not, or how I can get the right
    > behaviour in a threaded program?

    I've done some more testing. It appears that when linked with lc_r,
    VTIME is completely ignored.

    As explained in termios(4), when VMIN>0, the read call will wait
    indefinitely for the first byte and then use VTIME as an interbyte
    timer. When using lc_r however, it'll return immediately after the
    first couple bytes read, even if that's less than VMIN.

    The case where VTIME==0 works as it should both with lc and lc_r.

    I dont have access to a box with -current, so I can't say if the same
    applies to it.

    I hope somebody understands this better or could at least give me a
    few pointers as to where to look in the source code.

    Thanks, tijl

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  • Next message: Don Lewis: "Re: 4-stable termios diff behaviour lc/lc_r"