Messages in this thread | | | Date | Mon, 18 Aug 2008 13:29:48 -0500 | From | Scott Wood <> | Subject | Re: ftrace introduces instability into kernel 2.6.27(-rc2,-rc3) |
| |
Steven Rostedt wrote: >> Should use a "b" constraint for %2, or you could get r0. > > I will make an updated patch. > >> Or, use an "m" >> constraint with %U2%X2 after the lwz/stw. > > The 'b' seems easier ;-)
The advantage of the latter is that it allows GCC to choose indexed or update instructions -- but that's merely an optimization. Switching to "b" is enough to avoid the potential bug.
>> %1 also needs to be an early clobber. > > Not exactly sure what you mean by the above.
%1 is written to before some inputs are consumed, so you need to use "=&r" rather than "=r" so that GCC won't use the same register for both.
-Scott
| |