Re: 4-stable termios diff behaviour lc/lc_r

From: Don Lewis (truckman_at_FreeBSD.org)
Date: 08/30/04

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    Date: Mon, 30 Aug 2004 12:38:42 -0700 (PDT)
To: tijl@ulyssis.org

    On 30 Aug, Tijl Coosemans wrote:

    > 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.

    This is not suprising. The way libc_r handles I/O is that it puts all
    the descriptors in non-blocking mode and uses poll() to figure out which
    threads to run. To work properly, libc_r would have to emulate VMIN
    internally.

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

    I would expect the same behaviour with libc_r on -CURRENT, but the other
    thread libraries should work properly.

    > 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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