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xen-devel
Re: [Xen-devel] question on the use of fs in evtchn.c
On Mon, Aug 09, 2004 at 10:40:10PM -0600, ron minnich wrote:
> The problem is that ffs will return -1 if l1 is 0. Yeah, I know, unlikely,
> but if it ever happens that l1 or l2 are 0, well, you're in for a fun
> time. In any event, the loop condition holds for both a valid result and
> an error, which may not be what you really want to do.
If you look at the definition of ffs in xen/include/asm-x86/bitops.h,
you'll see that we return 0 in the "error" case (i.e. input was 0).
> In the plan 9 port this is:
> while ( (l1i = ffs(l1)) > 0 )
If your ffs indeed returns -1 if l1 is 0, shouldn't your test be >= 0?
Or does it never return 0?
christian
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