lkml.org 
[lkml]   [2007]   [Jan]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: PATCH - x86-64 signed-compare bug, was Re: select() setting ERESTARTNOHAND (514).
    On Thursday January 11, ak@suse.de wrote:
    > > Just a 'me too' at this point.
    > > The X server on my shiny new notebook (Core 2 Duo) occasionally dies
    > > with 'select' repeatedly returning ERESTARTNOHAND. It is most
    > > annoying!
    >
    > Normally it should be only visible in strace. Did you see it without
    > strace?

    No, only in strace.

    >
    > >
    > > You don't mention in the Email which kernel version you use but I see
    > > from the web page you reference it is 2.6.19.1. I'm using
    > > 2.6.18.something.
    > >
    > > I thought I'd have a quick look at the code, comparing i386 to x86-64
    > > and guess what I found.....
    > >
    > > On x86-64, regs->rax is "unsigned long", so the following is
    > > needed....
    >
    > regs->rax is unsigned long.
    > I don't think your patch will make any difference. What do you think
    > it will change?

    If regs->rax is unsigned long, then I would think the compiler would
    be allowed to convert

    switch (regs->rax) {
    case -514 : whatever;
    }

    to a no-op, as regs->rax will never have a negative value.

    However it appears that the current compiler doesn't make that
    optimisation so I guess I was too hasty.

    Still, I think it would be safer to have the cast, in case the compiler
    decided to be clever.... or does the C standard ensure against that?

    Sorry for the noise,

    NeilBrown
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-01-11 02:39    [W:0.023 / U:31.652 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site