Re: [PATCH] __up_read and gcc-3.0

["Petr Vandrovec" <VANDROVE@vc.cvut.cz>]

On 11 May 01 at 9:13, Tom Leete wrote:
> >         __asm__ __volatile__(
> >                 "# beginning __up_read\n\t"
> > +               "  movl      %2,%%edx\n\t"
> >  LOCK_PREFIX    "  xadd      %%edx,(%%eax)\n\t" /* subtracts 1, returns the old value */
> >                 "  js        2f\n\t" /* jump if the lock is being waited upon */
> >                 "1:\n\t"
> 
> My solution to this was to relax +d(tmp) to +m(tmp). Posted a few days ago.
> I have larger problems with 2.4.5-pre1 and have not gone back to check what
> comes out. Being a product of pure reason (and not much of that), mine
> deserves suspicion.

Changing +d => +m could generate 'xadd (%%xyz),(%%eax)' which does not exist.
Maybe +r, but in this case do not forget to add push/pop %%edx around
call to rwsem_wake. Otherwise you can have some corruption if gcc decides
to use %edx for some local variable around __up_read.
                                                    Best regards,
                                                        Petr Vandrovec
                                                        vandrove@vc.cvut.cz