Messages in this thread | | | From | Neil Brown <> | Date | Thu, 11 Jan 2007 12:02:53 +1100 | Subject | Re: PATCH - x86-64 signed-compare bug, was Re: select() setting ERESTARTNOHAND (514). |
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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,
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